Document:

<PAGE>   1
                                                                   Exhibit 10.23

                                RIVERSIDE CENTER
                              NEWTON, MASSACHUSETTS

                             OFFICE LEASE AGREEMENT

                                     BETWEEN

       EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED LIABILITY COMPANY
                                  ("LANDLORD")

                                       AND

  ALLAIRE CORPORATION, A CORPORATION ORGANIZED UNDER THE LAWS OF THE STATE OF
                              DELAWARE ("TENANT")

<PAGE>   2
                                TABLE OF CONTENTS

I. BASIC LEASE INFORMATION.....................................................1

II. LEASE GRANT................................................................4

III. ADJUSTMENT OF COMMENCEMENT DATE; POSSESSION...............................5

IV. RENT.......................................................................9

V. COMPLIANCE WITH LAWS; USE..................................................13

VI. SECURITY DEPOSIT..........................................................14

VII. SERVICES TO BE FURNISHED BY LANDLORD.....................................16

VIII. LEASEHOLD IMPROVEMENTS..................................................17

IX. REPAIRS AND ALTERATIONS...................................................17

X. USE OF ELECTRICAL SERVICES BY TENANT.......................................19

XI. ENTRY BY LANDLORD.........................................................19

XII. ASSIGNMENT AND SUBLETTING................................................20

XIII. LIENS...................................................................22

XIV. INDEMNITY AND WAIVER OF CLAIMS...........................................23

XV. INSURANCE.................................................................23

XVI. SUBROGATION..............................................................23

XVII. CASUALTY DAMAGE.........................................................24

XVIII. CONDEMNATION...........................................................25

XIX. EVENTS OF DEFAULT........................................................25

XX. REMEDIES..................................................................26

XXI. LIMITATION OF LIABILITY..................................................27

XXII. NO WAIVER...............................................................27

XXIII.  QUIET ENJOYMENT.......................................................27

XXIV. RELOCATION..............................................................27

XXV. HOLDING OVER.............................................................27

XXVI. SUBORDINATION TO MORTGAGES; ESTOPPEL CERTIFICATE........................28

XXVII. ATTORNEYS'FEES.........................................................28

XXVIII. NOTICE................................................................28

XXIX.EXCEPTED RIGHTS..........................................................29

XXX. SURRENDER OF PREMISES....................................................29

XXXI. MISCELLANEOUS...........................................................29

XXXII.ENTIRE AGREEMENT........................................................32

EXHIBIT A - OUTLINE AND LOCATION OF FIRST FLOOR PREMISES OF ONE RIVERSIDE CENTER
EXHIBIT A-1 - OUTLINE AND LOCATION OF SECOND FLOOR PREMISES OF ONE RIVERSIDE
CENTER
EXHIBIT A-2 - OUTLINE AND LOCATION OF THIRD FLOOR PREMISES OF ONE RIVERSIDE
CENTER
EXHIBIT A-3 - OUTLINE AND LOCATION OF FIRST FLOOR PREMISES OF TWO RIVERSIDE
CENTER
EXHIBIT A-4 - OUTLINE AND LOCATION OF SECOND FLOOR PREMISES OF TWO RIVERSIDE
CENTER
EXHIBIT B - RULES AND REGULATIONS
EXHIBIT C - COMMENCEMENT LETTER
EXHIBIT D - WORK LETTER
EXHIBIT E - ADDITIONAL TERMS AND CONDITIONS
EXHIBIT F - NOTICE OF LEASE
EXHIBIT G - LEGAL DESCRIPTION OF PROPERTY
EXHIBIT H - BUILDING PLAN
EXHIBIT I - SAMPLE LETTER OF CREDIT
EXHIBIT J - FORM OF NON-DISTURBANCE AGREEMENT
EXHIBIT K - LOCATION OF PARKING STRUCTURE SIGN

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EXHIBIT L - LOCATION OF ONE RIVERSIDE CENTER SIGN
EXHIBIT M - BASE BUILDING SCOPE
EXHIBIT N - SAMPLE CLEANING SPECIFICATIONS
EXHIBIT O - ENTRY SIGNAGE
EXHIBIT P - FIRST EXPANSION SPACE

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<PAGE>   4

                             OFFICE LEASE AGREEMENT

     This Office Lease Agreement (the "Lease") is made and entered into as of
the 23rd day of November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A
DELAWARE LIMITED LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A
CORPORATION ORGANIZED UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant").

I.   BASIC LEASE INFORMATION.

     A.   "Building" shall mean the building to be constructed on the land
          described in EXHIBIT G attached hereto, commonly known as Riverside
          Center, and having an address of 275 Grove Street, Newton, MA.
          Landlord and Tenant acknowledge that: (i) the "Building", as defined
          herein, consists of three (3) buildings commonly known as One
          Riverside Center, Two Riverside Center and Three Riverside Center, and
          (ii) the Premises (hereinafter defined) are located entirely in One
          Riverside Center and Two Riverside Center. A copy of a plan showing
          the Building and the location of One Riverside Center and Two
          Riverside Center within the Building is attached hereto as EXHIBIT H.

     B.   "Rentable Square Footage of the Building" is deemed to be 494,710
          square feet.

     C.   "Premises" shall mean the area shown on EXHIBITS A, A-1, A-2, A-3 AND
          A-4 to this Lease and identified as Suites #1-100, 1-200, 1-300,
          2-100, and 2-200. The Premises are located on floors one (1), two (2)
          and three (3) of One Riverside Center and floors one (1) and two (2)
          of Two Riverside Center. The "Rentable Square Footage of the Premises"
          is deemed to be approximately 270,446 square feet, consisting of
          223,300 square feet in One Riverside Center (sometimes referred to as
          the "One Riverside Center Premises") and 47,146 square feet in Two
          Riverside Center (sometimes referred to as the "Two Riverside Center
          Premises"). Tenant acknowledges that Landlord has not yet determined
          the exact location of the building management office on the first
          floor of Two Riverside Center and, as such, EXHIBIT A-3 shows the
          approximate location of the portion of the Two Riverside Center
          Premises that is located on the first floor of Two Riverside Center.
          Landlord and Tenant will work together in good faith to agree upon the
          exact location of the management office and, accordingly, the portion
          of the Two Riverside Center Premises on the first floor of Two
          Riverside Center by no later than December 15, 1999; provided that:
          (i) the management office will be located in either the southwesterly
          or northeasterly corners of the first floor of Two Riverside Center;
          and (ii) in no event shall the management office be located so as to
          segregate Tenant's space on the first floor of Two Riverside Center,
          it being agreed that Tenant's space on the first floor shall be
          demised as one contiguous parcel of space. In the event that Landlord
          and Tenant do not agree on the location of the management office by
          December 15, 1999, Tenant shall have the right to designate the
          location of the Two Riverside Premises on the first floor of Two
          Riverside Center and the management office in either the southwesterly
          corner or northeasterly corner. All corridors and restroom facilities
          located on floors one, two and three of One Riverside Center, floor
          two of Two Riverside Center and any other floors leased by Tenant in
          their entirety shall be considered part of the Premises. The total
          Rentable Square Footage of the Premises and of the Building has been
          determined from the approved permit set of construction drawings,
          without field measurement, based upon the 1996 BOMA standard of
          measurement. Notwithstanding the foregoing, Landlord, at its sole cost
          and expense within six (6) months following the Substantial Completion
          (hereinafter defined) of the Base Building Work (hereinafter defined),
          shall cause the Rentable Square Footage of the Premises, the Rentable
          Square Footage of the Building and the Rentable Square Footage of the
          First Expansion Space (defined in Section IV of Exhibit E) to be field
          measured by an architect retained by Landlord. If, as a result of such
          field measurement, it is determined that the Rentable Square Footage
          of the Premises, First Expansion Space or the Rentable Square Footage
          of the Building has been misstated by more than 1%, Landlord and
          Tenant shall promptly enter into an amendment to this Lease to restate
          the Rentable Square Footage of the Building, First Expansion Space,
          and/or the Rentable Square Footage of the Premises, as the case may
          be, to reflect the actual square footage pursuant to the field
          measurement. If such field measurement does not disclose a variance of
          1% or more, any variance that is disclosed shall be considered by
          Landlord and Tenant to be immaterial and shall not result in an
          amendment of the Rentable Square Footage of the Building, First
          Expansion Space, and/or the Rentable Square Footage of the Premises,
          as the case may be. Landlord and Tenant acknowledge that the amendment
          of the Rentable Square Footage of the Premises will affect the Base
          Rent, Allowance (hereinafter defined) and the Architectural and
          Engineering Allowance (hereinafter defined), as such amounts are
          determined on a "per

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          square foot" basis. Landlord and Tenant further acknowledge that the
          amendment of either the Rentable Square Footage of the Premises or the
          Rentable Square Footage of the Building will affect Tenant's Pro Rata
          Share (as hereinafter defined).

     D.   "Base Rent" shall mean the following with respect to the One Riverside
          Center Premises and the Two Riverside Center Premises:

          Base Rent Schedule for the One Riverside Center Premises
          --------------------------------------------------------

<TABLE>
<CAPTION>
                              ANNUAL RATE        ANNUAL                MONTHLY
          PERIOD            PER SQUARE FOOT     BASE RENT             BASE RENT
          ------            ---------------     ---------             ---------
<S>                             <C>           <C>                   <C>
          Months 1-6            $32.50        $4,773,632.52         $397,802.71
          Months 7-15           $32.50        $6,015,457.52         $501,288.13
          Months 16-60          $32.50        $7,257,249.96         $604,770.83
          Months 61-120         $32.50        $7,927,149.96         $660,595.83
</TABLE>

          Landlord and Tenant acknowledge that, notwithstanding the Rentable
          Square Footage of the One Riverside Center Premises, the foregoing
          schedule of Base Rent has been calculated based upon 146,881 rentable
          square feet with respect to months 1 - 6 of the Term and upon 185,091
          rentable square feet with respect to months 7 - 15 of the Term. Tenant
          shall be required to pay Base Rent based upon such reduced square
          footage amounts regardless of whether Tenant occupies more or less
          square footage of the One Riverside Center Premises during such
          period.

          Base Rent Schedule for the Two Riverside Center Premises
          --------------------------------------------------------

<TABLE>
<CAPTION>
                                      ANNUAL RATE       ANNUAL         MONTHLY
          PERIOD                    PER SQUARE FOOT    BASE RENT      BASE RENT
          ------                    ---------------    ---------      ---------
<S>                                     <C>          <C>            <C>
          Months 1-60                   $34.00       $1,602,963.96  $133,580.33
          Months 61-Termination Date    $36.00       $1,697,256.00  $141,438.00
</TABLE>

          In the event the Rentable Square Footage of the Premises is adjusted
          pursuant to Section I.C. above, the foregoing square footage amounts
          shall be adjusted up or down by the same percentage as the adjustment
          of the overall Premises. The schedule of Base Rent shall also be
          adjusted based upon the new square footage calculations. In the event
          that the Term does not commence on the first day of a calendar month,
          the schedule of Base Rent shall be deemed to reflect lease months, as
          opposed to calendar months, provided, however, payments of Base Rent
          shall be made on a calendar month basis. For example, if the
          Commencement Date occurs on July 15, 2000, the first lease month shall
          reflect the period of July 15, 2000 through August 14, 2000. In the
          event that Base Rent adjusts on a day other than the first day of a
          calendar month, the total monthly Base Rent for such month shall
          reflect a blended rate based upon the number of days in such calendar
          month during which each rate (or square footage) is in effect.
          Notwithstanding the foregoing, Base Rent shall always be payable on or
          before the first day of each calendar month.

     E.   "Tenant's Pro Rata Share": 54.6676%, subject to adjustment as provided
          in this Lease.

     F.   "Tax Base Year" shall be the Fiscal Year 2001 (i.e. July 1, 2000
          through June 30, 2001). For purposes hereof, the term "Fiscal Year"
          shall mean the Tax Base Year and every subsequent period of July 1st
          through June 30th. The "Expense Base Year" shall be the period
          beginning on the Commencement Date and ending on the day prior to the
          first anniversary of the Commencement Date. For example, if the
          Commencement Date occurs on July 15, 2000, the Expense Base Year shall
          mean the period beginning on July 15, 2000 and ending on July 14,
          2001. Expenses for the Expense Base Year and subsequent years shall be
          adjusted to reflect 95% occupancy in accordance with the terms and
          conditions of Section IV.C.

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<PAGE>   6

     G.   "Term" shall mean the following with respect to the One Riverside
          Center Premises and the Two Riverside Center Premises:

          Term for the One Riverside Center Premises
          ------------------------------------------

          A period of 120 months, as the same may be extended in accordance with
          the terms hereof. The "Term" for the One Riverside Center Premises
          shall commence on the later to occur of (1) July 1, 2000 (the "Target
          Commencement Date"); or (2) the date upon which Landlord Work in the
          One Riverside Premises is "Substantially Complete", as such date is
          determined pursuant to Section III.A. hereof (such date being referred
          to as the date of "Substantial Completion"); or (3) the date on which
          Landlord delivers full possession of the One Riverside Center Premises
          to Tenant (the later to occur of such dates being defined as the
          "Commencement Date"). The "Termination Date" shall, unless sooner
          terminated as provided herein, mean the last day of the Term as the
          same may be extended as provided herein.

          Term for the Two Riverside Center Premises
          ------------------------------------------

          A period of months, days and years, as the same may be extended in
          accordance with the terms hereof, commencing on the Two Riverside
          Center Premises Commencement Date (hereinafter defined) and ending on
          the Termination Date as determined above with respect to the One
          Riverside Center Premises, it being agreed that the entire Premises
          (i.e. the One Riverside Center Premises and Two Riverside Center
          Premises) shall always expire on the same date. The "Two Riverside
          Center Premises Commencement Date" shall occur on the later to occur
          of (1) August 1, 2000 (the "Two Riverside Center Target Commencement
          Date"); or (2) the date upon which Landlord Work in the Two Riverside
          Premises is "Substantially Complete", as such date is determined
          pursuant to Section III.A. hereof (such date being referred to as the
          date of "Substantial Completion"); (3) the date on which Landlord
          delivers full possession of the Two Riverside Center Premises to
          Tenant; or (4) the Commencement Date with respect to the One Riverside
          Center Premises. Landlord and Tenant acknowledge that the defined
          terms of "Substantially Complete" and "Substantial Completion" shall
          have the same meaning, but shall be applied separately, with respect
          to the One Riverside Center Premises and the Two Riverside Center
          Premises.

          Except as provided elsewhere in this Lease to the contrary, the
          adjustment of the Commencement Date and, accordingly, the postponement
          of Tenant's obligation to pay Rent shall be Tenant's sole remedy and
          shall constitute full settlement of all claims that Tenant might
          otherwise have against Landlord by reason of the Landlord Work in the
          One Riverside Center Premises not being Substantially Complete on the
          Target Commencement Date or the Two Riverside Center Premises not be
          Substantially Complete on the Two Riverside Premises Target
          Commencement Date. Landlord, in accordance with Section III.A. below,
          shall provide Tenant with notice of the date on which Landlord
          reasonably estimates that the Landlord Work will be Substantially
          Complete (as defined in Section III.A herein) in the One Riverside
          Center Premises and the Two Riverside Center Premises. Promptly after
          the determination of the Commencement Date and the Two Riverside
          Center Premises Commencement Date, Landlord and Tenant shall enter
          into a commencement letter agreement in the form attached as EXHIBIT
          C.

     H.   Tenant allowances: An Allowance (defined in Exhibit D) of Six Million
          Seven Hundred Sixty-One Thousand One Hundred Fifty and 00/100 Dollars
          ($6,761,150.00) to be applied toward the cost of the Landlord Work and
          an Architectural and Engineering Allowance (defined in Exhibit D) of
          $540,892.00 to be applied toward the cost of preparing Plans (defined
          in Exhibit D) for the Landlord Work.

     I.   "Security Deposit": Initially $8,477,000.00. Fifty percent (50%) of
          the Security Deposit (i.e. $4,238,500.00) shall be due and payable
          upon the execution of this Lease by Tenant. The remaining fifty
          percent (50%) of the Security Deposit (i.e. $4,238,500.00) shall be
          payable during the performance of the Landlord Work in accordance with
          the terms and conditions of Article VI. The Security Deposit shall be
          subject to increase and decrease in accordance with the terms and
          conditions of Article VI.

     J.   "Guarantor(s)": None.

     K.   "Broker(s)": Spaulding & Slye.

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<PAGE>   7

     L.   "Permitted Use": General office use.

     M.   "Notice Addresses":

          Tenant:

          On and after the Commencement Date, notices shall be sent to Tenant at
          the Premises, Attention: General Counsel. Prior to the Commencement
          Date, notices shall be sent to Tenant at the following address:

          Allaire Corporation
          One Alewife Center
          Third Floor
          Cambridge, Massachusetts  02140
          Attention: General Counsel
          Phone #:  617.761.2260
          Fax #:  617.761.2201

          A copy of any notices of default shall be sent to:

          Foley, Hoag & Eliot LLP
          One Post Office Square
          Boston, MA 02109
          Attention: Robert L. Birnbaum, Esq.
          Phone #: 617.832.1000
          Fax #: 617.832.7000

           Landlord:                              With a copy to:

           Wellesley Office Park                  Equity Office Properties
           c/o Equity Office Properties           Two North Riverside Plaza
           65 William Street                      Suite 2200
           Wellesley, MA 02181                    Chicago, Illinois 60606
           Attention: Building Manager            Attention: Northeast Regional
                                                  Counsel

          Rent (defined in Section IV.A) is payable to the order of EQUITY
          OFFICE PROPERTIES at the following address:

          EOP Operating Limited Partnership, as agent
          P.O. Box 30162
          Hartford, CT 06150-0162

     N.   "Business Day(s)" are Monday through Friday of each week, exclusive of
          New Year's Day, Memorial Day, Independence Day, Labor Day,
          Thanksgiving Day and Christmas Day ("Holidays"). Landlord may
          designate additional Holidays, provided that the additional Holidays
          are commonly recognized by other office buildings in the area where
          the Building is located.

     O.   "Landlord Work" means the work that Landlord is obligated to perform
          in the Premises pursuant to the work letter agreement (the "Work
          Letter") attached as EXHIBIT D.

     P.   "Law(s)" means all applicable statutes, codes, ordinances, orders,
          rules and regulations of any municipal or governmental entity.

     Q.   "Normal Business Hours" for the Building are 8 A.M. to 6 P.M. on
          Business Days and 8 A.M. to 1 P.M. on Saturdays.

     R.   "Property" means the Building and the parcel of land on which it is
          located described in EXHIBIT G.

     S.   "Base Building Work" shall mean the work that Landlord is obligated to
          perform as described in the Base Building Scope attached as EXHIBIT M.

                                       4

<PAGE>   8

II.  LEASE GRANT.

     Landlord leases the Premises to Tenant and Tenant leases the Premises from
Landlord, together with the right in common with others to use any portions of
the Building and Property that are designated by Landlord for the common use of
tenants and others, such as sidewalks, common corridors, elevator foyers, and
other portions of the Building and Property that reasonably necessary for access
to the Building and the Premises; unreserved parking areas; restrooms; and
vending areas (the "Common Areas").

III. ADJUSTMENT OF COMMENCEMENT DATE; POSSESSION.

     A.   The Landlord Work with respect to each of the One Riverside Center
          Premises and the Two Riverside Center Premises shall be deemed to be
          "Substantially Complete" on the date that all of the following
          conditions have been satisfied (or would have been satisfied absent
          any Tenant Delays [hereinafter defined]): (i) All of the Landlord's
          Work with respect to the One Riverside Center Premises or the Two
          Riverside Center Premises (as the case may be) has been performed (as
          evidenced by Landlord's architect's certificate of substantial
          completion as hereinbelow provided), other than any minor details of
          construction, mechanical adjustment or any other matter, the
          noncompletion of which does not materially interfere with Tenant's use
          and occupancy of the One Riverside Center Premises or the Two
          Riverside Center Premises (as the case may be) as more particularly
          set forth below and in Section III.C. below ("Punchlist Items").
          Landlord acknowledges that the construction of demising walls, and
          installation of glass partitions, doors and carpet and the completion
          of other work that is necessary to allow Tenant to install its
          furniture and equipment in the One Riverside Center Premises or the
          Two Riverside Center Premises (as the case may be) shall not be
          considered to be Punchlist Items but shall be considered conditions
          precedent to Substantial Completion; (ii) Landlord has received a
          temporary or permanent (non-conditional) certificate of occupancy with
          respect to the One Riverside Center Premises or the Two Riverside
          Center Premises (as the case may be), (iii) the Base Building Work in
          One Riverside Center or Two Riverside Center (as the case may be) and
          a means of safe ingress and egress and all facilities reasonably
          necessary to Tenant's use and occupancy of the One Riverside Center
          Premises or the Two Riverside Center Premises (as the case may be),
          including corridors, elevators and stairways, heating, ventilating,
          air-conditioning, fire/life safety, Building security systems,
          sanitary, water, electrical, lighting, telephone and data to the
          demarcation room (ready for connection to Tenant's internal system)
          and power facilities, have been installed and are in good operating
          order and available to Tenant in accordance with Landlord's
          obligations under the Lease; (iv) the ground floor lobby in the
          Building has been substantially completed, subject to Punchlist Items,
          and lobby furniture shall have been installed, (v) there is adequate
          parking available to provide Tenant parking spaces at the Property
          based on a ratio of 3 spaces for each 1000 rentable square feet of
          Premises, (vi) a cafeteria or other food service provider is open for
          business in the Building, (vii) workout facilities are open for use in
          the Building, and (viii) parking lot and outdoor lighting is installed
          and operational. If Landlord has not obtained a permanent
          non-conditional certificate of occupancy as of the Commencement Date,
          Landlord will obtain the same within a reasonable time after the
          Commencement Date.

          From time to time upon request by Tenant or Tenant's designated
          representative, Landlord shall advise Tenant of the progress of the
          Landlord Work and Base Building Work in the Premises and the
          approximate date on which Landlord Work with respect to each portion
          of the Premises will be Substantially Complete. In addition, whether
          or not Tenant requests the same, Landlord will use reasonable efforts
          to provide Tenant with at least 30 days prior notice of the date on
          which Landlord reasonably believes the Landlord Work will be
          Substantially Complete; provided that Landlord's failure to provide
          such notice shall not be a default by Landlord or postpone the
          Commencement Date or the Two Riverside Center Premises Commencement
          Date (as the case may be). Tenant acknowledges that any such estimate
          by Landlord shall not be binding on Landlord and shall not be
          construed as anything more than a good faith estimate based upon the
          circumstances known to Landlord at such time.

     B.   Notwithstanding anything herein to the contrary, if Landlord is
          delayed in the performance of the Landlord Work as a result of any
          Tenant Delay(s) (defined below), the Landlord Work shall be deemed to
          be Substantially Complete on the date that Landlord could reasonably
          have been expected to Substantially Complete the Landlord Work absent
          any Tenant Delay, calculated by determining the actual number of days
          that Substantial Completion of the Landlord Work was delayed by such
          Tenant Delay(s).

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<PAGE>   9

          Landlord agrees to provide Tenant with written notice of any Tenant
          Delay(s) as soon as reasonably possible after Landlord first becomes
          aware of such Tenant Delay(s), which notice shall include reasonable
          detail describing the cause of the Tenant Delay and, to the extent the
          same can reasonably be determined at such time (e.g. a long lead time
          item or changes to plans), Landlord's good faith estimate of the
          length of the Tenant Delay. For purposes hereof, the term "Tenant
          Delay" shall mean

          1.   Tenant's failure to furnish information in accordance with the
               Work Letter or to respond to any reasonable request by Landlord
               for any approval or information within any time period
               prescribed, or if no time period is prescribed, then within five
               (5) Business Days of such request, provided that a "Tenant Delay"
               shall not be deemed to have occurred unless Tenant's failure to
               respond or furnish information continues for one (1) additional
               Business Day after written notice of such failure is given to
               Tenant, which written notice may be delivered by messenger or
               other form of personal delivery; or

          2.   Subject to the provisions of the Work Letter, Tenant's selection
               of equipment or materials that have long lead times after first
               being informed by Landlord that the selection may result in a
               Tenant Delay, it being agreed that Landlord will use reasonable
               efforts to identify and order such items as soon as possible
               after receipt of Tenant's Design Development Plans (as defined in
               the Work Letter). Notwithstanding the foregoing, if specific
               materials for the Landlord Work are unavailable and there are no
               reasonable substitutes available for such materials, such
               circumstance shall be considered to be an event of Force Majeure,
               and not a Tenant Delay. Aesthetics shall not be taken into
               consideration in determining whether a particular item is
               available without reasonable substitute, it being agreed that
               such decision shall be made solely on the basis of functionality;
               or

          3.   Tenant's failure to complete Plans (defined in the Work Letter)
               by their respective due dates pursuant to the terms and
               conditions of the Work Letter, or any changes to the Plans that
               are requested by Tenant after approval of the Plans by Landlord;
               or

          4.   Subject to subsection III.D. below, the performance of work in
               the Premises (e.g. the installation of cabling, furniture and
               equipment) by persons or entities employed by Tenant (all such
               work and such persons or entities being subject to the prior
               reasonable approval of Landlord) to the extent that the same
               materially interferes with the completion of Landlord Work or
               Base Building Work; or

          5.   Any delays caused by (i) an uncured Monetary Default (as defined
               in Section XIX) by Tenant, including, without limitation,
               Tenant's failure to provide Landlord with the Security Deposit,
               or (ii) the voluntary or involuntary bankruptcy of Tenant; or

          6.   Subject to subsection III.D. below, any delay resulting from
               Tenant's having taken possession of the Premises in accordance
               with Section III.D. below prior to substantial completion of the
               Landlord Work, which delay continues for one (1) Business Day
               after Landlord provides Tenant with written notice of such delay,
               which written notice may be delivered by messenger or other form
               of personal delivery.

     C.   Subject to (i) Substantial Completion of the Landlord Work, (ii) the
          correction of Punchlist Items set forth on a punch list mutually
          prepared by Landlord and Tenant promptly following Substantial
          Completion of the Landlord Work, (iii) latent defects, and (iv)
          necessary corrections and adjustments to seasonal items such as
          heating and air conditioning that are not readily discoverable by
          Tenant on or about the date of Substantial Completion, by taking
          possession of the One Riverside Center Premises or the Two Riverside
          Center Premises (as the case may be) for the purpose of operating its
          business therein, Tenant is deemed to have accepted such portion of
          the Premises and agreed that such portion of the Premises is in good
          order and satisfactory condition, with no representation or warranty
          by Landlord as to the condition of such portion of the Premises or the
          Building or suitability thereof for Tenant's use. Tenant shall be
          liable for all costs necessary to correct damage caused by Tenant in
          moving and installing its furniture, equipment or other personal
          property in the Premises. Notwithstanding anything herein to the
          contrary, Landlord's obligation to correct any latent defects with
          respect to items that Tenant is required to maintain and repair
          pursuant to Section IX.A. shall be limited to the terms and conditions
          of any warranties received by Landlord in connection with the
          performance of the Landlord Work, it being agreed that Landlord shall
          obtain a 1 year warranty of workmanship for the Landlord Work. Within
          45 days following the Substantial Completion of the Landlord Work,
          Landlord and Tenant shall

                                       6

<PAGE>   10

          conduct a second inspection of such portion of the Premises and
          prepare a second punch list with respect to any items that were not
          adequately completed from the first punch list and any items that were
          not reasonably discoverable during the first inspection (including,
          without limitation, latent defects). Landlord shall use good faith
          efforts to correct any items listed on the first and second punch list
          as soon as reasonably possible. The cost of correcting any Punchlist
          Items shall be included as part of the contract price for the Landlord
          Work, it being understood that the performance of punchlist work shall
          not be considered to be a change order or otherwise result in an
          additional cost to Tenant. Landlord shall use reasonable efforts to
          cause the Punch List Items to be completed (and to perform work in
          general) in a manner that minimizes the level of interference with
          Tenant's use of the Premises; provided that Landlord shall not be
          obligated to incur any additional costs to complete the Punchlist
          Items or to perform necessary maintenance and repairs at times other
          than Normal Business Hours.

     D.   If Tenant takes possession of the One Riverside Center Premises or the
          Two Riverside Center Premises before the Commencement Date or the Two
          Riverside Center Premises Commencement Date, respectively, such
          possession shall be subject to the terms and conditions of this Lease
          and Tenant shall pay Rent (defined in Section IV.A.) to Landlord for
          each day of possession before the Commencement Date; provided,
          however, except for the cost of services requested by Tenant, Tenant
          shall not be required to pay Rent for any days of possession before
          the Commencement Date unless Tenant shall be actively using the
          Premises for the conduct of Tenant's business. Notwithstanding
          anything herein to the contrary, Landlord agrees that Tenant shall
          have access to each portion of the Premises at least thirty (30) days
          prior to the Commencement Date or the Two Riverside Center Premises
          Commencement Date, as the case may be (the "Early Access Period") for
          the sole purpose of installing voice and data cabling and equipment
          for Tenant's data center, build lab and LAN closets. Landlord and
          Tenant agree to work together in good faith to schedule appropriate
          times for Tenant's contractors and employees to install such cable and
          equipment during the Early Access Period so as to allow the Landlord
          Work and the permitted installation work of Tenant to be performed on
          schedule and minimize or eliminate any Tenant Delay(s); provided that,
          if Tenant performs within such schedule, such installation work shall
          not be deemed to contribute to Tenant Delay(s). If, in Landlord's
          reasonable discretion, such work can be performed without adversely
          affecting the performance of the Landlord Work or adversely affecting
          the date on which Landlord can reasonably expect to receive a
          certificate of occupancy for the Premises, Landlord will permit Tenant
          to commence installing its other furniture, equipment and personal
          property in the Premises during the Early Access Period.

     E.   Late Completion Penalties and Termination Rights.
          -------------------------------------------------

          1.   If Landlord fails to commence the performance of the Landlord
          Work on or before June 1, 2000 (the "First Termination Date"), Tenant
          may terminate this Lease by giving Landlord written notice of
          termination on or before the date on which Landlord commences to
          perform Landlord Work in the Premises.

          2.   If the Commencement Date has not occurred on or before September
          1, 2000 (the "One Riverside Premises Outside Completion Date"), Tenant
          shall be entitled to a rent abatement (the "Late Completion
          Abatement") following the Commencement Date of $13,078.45 for every
          day in the period beginning on the One Riverside Premises Outside
          Completion Date and ending on the earlier to occur of (i) the
          Commencement Date, or (ii) January 1, 2001. If the Two Riverside
          Center Premises Commencement Date has not occurred on or before
          October 1, 2000 (the "Two Riverside Center Premises Outside Completion
          Date"), Tenant shall be entitled to a rent abatement (also referred to
          as a "Late Completion Abatement") following the Two Riverside Center
          Premises Commencement Date of $4,392.00 for every day in the period
          beginning on the Two Riverside Center Premises Outside Completion Date
          and ending on the Two Riverside Premises Center Commencement Date,
          unless this Lease is sooner terminated. In addition, if all of the
          Additional Abatement Conditions (hereinafter defined) occur, Tenant
          shall be entitled to receive a rent abatement following the
          Commencement Date in a amount equal to the Additional Late Completion
          Abatement (hereinafter defined). The Additional Late Completion
          Abatement shall be applied against Rent due under the Lease from and
          after the full application of the Late Completion Abatement. For
          purposes hereof:

               a.   The "Additional Abatement Conditions" are: (i) the
                    Commencement Date (i.e. with respect to the One Riverside
                    Center Premises) does not occur by the

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<PAGE>   11

                    Outside Completion Date; (ii) Tenant has entered into (1)
                    one or more subleases or assignments with third parties
                    (each being referred to as a "Alewife Sublease") for all or
                    a portion of the premises currently leased by Tenant at One
                    Alewife Center, Cambridge, MA (the "One Alewife Premises"
                    and such lease being referred to herein as the "One Alewife
                    Lease"), and/or (2) an agreement with the landlord of the
                    One Alewife Premises for the recapture of the One Alewife
                    Premises or a portion thereof (the "Alewife Recapture");
                    (iii) as a result of Landlord's failure to complete the
                    Landlord Work in the One Riverside Center Premises and
                    Tenant's inability to move into the One Riverside Center
                    Premises, Tenant is unable to deliver possession of any
                    premises under a Alewife Sublease or the Alewife Recapture
                    on or before the later to occur of (y) the Outside
                    Commencement Date, or (z) the commencement date of the
                    Alewife Sublease and/or the surrender date under the Alewife
                    Recapture, as the case may be; and (iv) as a result of
                    Tenant's inability to deliver possession on or before the
                    later of the dates described in (iii), the
                    subtenant/assignee under the Alewife Sublease terminates the
                    Alewife Sublease, and/or Tenant incurs penalties/damages
                    under the One Alewife Lease or the Alewife Recapture (such
                    penalties/damages being referred to herein as the "Alewife
                    Penalties").

               b.   The "Additional Late Completion Abatement" shall be an
                    amount equal to the lesser of: (i) $500,000.00 or (ii) the
                    total sum of the Alewife Sublease Lost Rent (hereinafter
                    defined) and the Alewife Penalties. The Alewife Sublease
                    Lost Rent shall be calculated separately for each Alewife
                    Sublease that satisfies the Additional Abatement Conditions
                    and added together to determine the total Alewife Sublease
                    Lost Rent. Tenant agrees to use reasonable efforts to
                    mitigate the amount of any Alewife Sublease Lost Rent. The
                    Alewife Sublease Lost Rent with respect to each individual
                    Alewife Sublease that satisfies the Additional Abatement
                    Conditions shall be an amount determined in accordance with
                    the following formula:

                    A - B = The Alewife Sublease Lost Rent

                    A = the total amount of rental that was payable under the
                    Alewife Sublease for the term of the Alewife Sublease
                    (exclusive of any unexercised renewal or extension options).

                    B = the total amount of rental that Tenant is entitled to
                    receive in connection with one or more subleases or
                    assignments (exclusive of any unexercised renewal or
                    extension options) that are entered into after the
                    termination of the Alewife Sublease with respect to the
                    portion of the One Alewife Premises that was covered by the
                    Alewife Sublease. Tenant may deduct from such total all
                    reasonable and customary expenses directly incurred by
                    Tenant attributable to such replacement subleases or
                    assignments, including brokerage fees, legal fees and
                    construction costs. If Tenant re-sublets/re-assigns less
                    than all of the space under a terminated Alewife Sublease,
                    the Alewife Sublease Lost Rent will be calculated separately
                    for each portion of the space that was (or wasn't')
                    re-sublet/re-assigned. For the purpose of calculating any
                    Alewife Sublease Lost Rent, it shall be assumed that all
                    rental is paid when due under each replacement sublease or
                    assignment, it being agreed that the risk of non-payment
                    under any replacement sublease or assignment shall be borne
                    by Tenant, not Landlord. Upon request by either party,
                    Landlord and Tenant shall enter into an amendment to this
                    Lease to document the total Alewife Sublease Lost Rent and
                    Alewife Penalties.

          3.   If the Commencement Date (i.e. with respect to the One Riverside
          Center Premises) does not occur by January 1, 2001 (the "Second
          Termination Date"), Tenant may terminate this Lease with respect to
          the entire Premises by giving Landlord written notice of termination
          on or before the earlier to occur of: (i) five (5) Business Days after
          the Second Termination Date; and (ii) the Commencement Date.
          Notwithstanding anything herein to the contrary, if Landlord
          determines that it will be unable to cause the Commencement Date to
          occur by the Second Termination Date, Landlord shall have the right to
          immediately cease its performance of the Landlord Work and provide
          Tenant with written notice (the "Outside Extension Notice") of such
          inability, which Outside Extension Notice shall set forth the date on
          which Landlord reasonably believes that the Commencement Date will
          occur. Upon receipt of the Outside Extension Notice, Tenant shall have
          the right to terminate this Lease by providing written notice of
          termination to Landlord within five (5) Business Days after the
          receipt of the Outside Extension Notice. In the event that Tenant does
          not terminate this Lease within such five (5) Business Day period, the
          Second Termination Date shall automatically be amended to be the date
          set forth in Landlord's Outside Extension Notice.

                                       8
<PAGE>   12

          4.   In the event Tenant terminates this Lease pursuant to subsections
          III.E.1 or III.E.3 above, this Lease shall be deemed null and void and
          of no further force and effect and Landlord shall promptly refund any
          Security Deposit and any portion of the Excess Costs (defined in the
          Work Letter attached hereto as EXHIBIT D) previously advanced by
          Tenant under this Lease and, so long as Tenant has not previously
          defaulted under any of its obligations under the Work Letter, the
          parties hereto shall have no further responsibilities or obligations
          to each other with respect to this Lease. Landlord and Tenant
          acknowledge and agree that: (i) the determination of the Commencement
          Date and the Two Riverside Premises Commencement Date shall take into
          consideration the effect of any Tenant Delays; and (ii) the First
          Termination Date, Outside Completion Date, Two Riverside Premises
          Outside Completion Date and Second Termination Date shall be postponed
          by the number of days the Commencement Date is delayed due to events
          of Force Majeure.

IV.  RENT.

     A.   PAYMENTS. As consideration for this Lease, Tenant shall pay Landlord,
          without any setoff or deduction, the total amount of Base Rent and
          Additional Rent due for the Term. "Additional Rent" means all sums
          (exclusive of Base Rent) that Tenant is required to pay Landlord.
          Additional Rent and Base Rent are sometimes collectively referred to
          as "Rent". Tenant shall pay and be liable for all rental, sales and
          use taxes (but excluding income taxes), if any, imposed upon or
          measured by Rent under applicable Law. Base Rent and recurring monthly
          charges of Additional Rent shall be due and payable in advance on the
          first day of each calendar month without notice or demand. All other
          items of Rent shall be due and payable by Tenant on or before 30 days
          after notice by Landlord. All payments of Rent shall be by good and
          sufficient check or by other means (such as electronic transfer)
          acceptable to Landlord. If Tenant fails to pay any item or installment
          of Rent when due, Tenant shall pay Landlord an administration fee
          equal to 5% of the past due Rent, provided that Tenant shall be
          entitled to a grace period of 5 days for the first 2 late payments of
          Rent in a given calendar year. If the Term commences on a day other
          than the first day of a calendar month or terminates on a day other
          than the last day of a calendar month, the monthly Base Rent and
          Tenant's Pro Rata Share of any Tax Excess (defined in Section IV.D.)
          or Expense Excess (defined in Section IV.B.) for the month shall be
          prorated based on the number of days in such calendar month.
          Landlord's acceptance of less than the correct amount of Rent shall be
          considered a payment on account of the earliest Rent due. No
          endorsement or statement on a check or letter accompanying a check or
          payment shall be considered an accord and satisfaction, and either
          party may accept the check or payment without prejudice to that
          party's right to recover the balance or pursue other available
          remedies. Tenant's covenant to pay Rent is independent of every other
          covenant in this Lease.

     B.   EXPENSE EXCESS. Tenant shall pay Tenant's Pro Rata Share of the
          amount, if any, by which Expenses (defined in Section IV.C.) for each
          calendar year during the Term (beginning on the day following the last
          day of the Expense Base Year) exceed Expenses for the Expense Base
          Year (the "Expense Excess"). If Expenses in any calendar year decrease
          below the amount of Expenses for the Expense Base Year, Tenant's Pro
          Rata Share of Expenses for that calendar year shall be $0. Landlord
          shall provide Tenant with a good faith estimate of the Expense Excess
          for each calendar year during the Term. On or before the first day of
          each month, Tenant shall pay to Landlord a monthly installment equal
          to one-twelfth of Tenant's Pro Rata Share of Landlord's estimate of
          the Expense Excess. If Landlord determines that its good faith
          estimate of the Expense Excess was incorrect by a material amount,
          Landlord may provide Tenant with a revised estimate. After its receipt
          of the revised estimate, Tenant's monthly payments shall be based upon
          the revised estimate; provided, however, Landlord shall submit no more
          than two such revisions in any calendar year. If Landlord does not
          provide Tenant with an estimate of the Expense Excess by January 1 of
          a calendar year, Tenant shall continue to pay monthly installments
          based on the previous year's estimate(s) until Landlord provides
          Tenant with the new estimate. Upon delivery of the new estimate, an
          adjustment shall be made for any month for which Tenant paid monthly
          installments based on the previous year's estimate(s). Tenant shall
          pay Landlord the amount of any underpayment within 30 days after
          receipt of the new

                                       9
<PAGE>   13

          estimate. Any overpayment shall be refunded to Tenant within 30 days
          or credited against the next due future installment(s) of Rent.

          As soon as practical following the end of each calendar year, Landlord
          shall furnish Tenant with a reasonably detailed statement of the
          actual Expenses and Expense Excess for the prior calendar year.
          Notwithstanding the foregoing, Landlord shall use reasonable efforts
          to provide Tenant with such statement no later than May 1st of each
          prior calendar year. If Landlord fails to provide Tenant with a
          statement by September 1st following each prior calendar year and such
          failure continues for 30 days after Landlord's receipt of a written
          notice from Tenant specifically requesting that Landlord furnish
          Tenant with a copy of such year end statement, Landlord shall be
          deemed to have waived its right to reconcile Expenses for such
          calendar year and recover any underpayment of Expenses from Tenant.
          Such waiver shall not be construed as to release Landlord of its
          obligation to furnish Tenant with a reconciliation of Expenses for
          such calendar year and to reimburse Tenant for any overpayment of
          Expenses. Tenant's written notice to Landlord shall clearly state that
          Landlord's failure to furnish a reconciliation of Expenses for the
          calendar year in question within 30 days shall be deemed to be a
          waiver of Landlord's right to recover any underpayment of Expenses
          from Tenant with respect to such calendar year.

          If the estimated Expense Excess for the prior calendar year is more
          than the actual Expense Excess for the prior calendar year, Landlord
          shall apply any overpayment by Tenant against Rent due or next
          becoming due, provided if the Term expires before the determination of
          the overpayment, Landlord shall, within 30 days after the delivery of
          the statement, refund any overpayment to Tenant after first deducting
          the amount of any Rent due. If the estimated Expense Excess for the
          prior calendar year is less than the actual Expense Excess for such
          prior year, Tenant shall pay Landlord, within 30 days after its
          receipt of the statement of Expenses, any underpayment for the prior
          calendar year.

     C.   EXPENSES DEFINED. "Expenses" means all costs and expenses (other than
          those expressly excluded herein) incurred in each calendar year in
          connection with operating, maintaining, repairing, and managing the
          Building and the Property, including, but not limited to:

          1.   Labor costs, including, wages, salaries, social security and
               employment taxes, medical and other types of insurance, uniforms,
               training, and retirement and pension plans, specifically
               excluding the personnel costs of any employee above the grade of
               general manager and the salaries of officers and executives of
               Landlord to the extent not directly connected with the operation
               of the Property.

          2.   Management fees in connection with the management of the
               Building, the cost of equipping and maintaining a management
               office, accounting and bookkeeping services, legal fees not
               attributable to leasing, lease enforcement or collection
               activity, and other overhead and administrative costs. Landlord,
               by itself or through an affiliate, shall have the right to
               directly perform or provide any services under this Lease
               (including management services), provided that the cost of any
               such services shall not exceed the cost that would have been
               incurred had Landlord entered into an arms-length contract for
               such services with an unaffiliated entity of comparable skill and
               experience.

          3.   The cost of services, including amounts paid to service providers
               and the rental and purchase cost of parts, supplies, tools and
               equipment. Except with respect to items that are rented by
               Landlord on an emergency basis in connection with the
               interruption of services, Expenses shall not include the rental
               cost of any items which are (or, if purchased, would be deemed)
               capital improvements (other than capital improvements permitted
               under subsection 6 below).

          4.   Premiums and deductibles paid by Landlord for insurance,
               including workers compensation, fire and extended coverage,
               earthquake, general liability, rental loss, elevator, boiler and
               other insurance customarily carried from time to time by owners
               of comparable office buildings.

          5.   Electrical Costs (defined below) and charges for water, gas,
               steam and sewer, but excluding those charges for which Landlord
               is entitled to be reimbursed by tenants (other than through
               Expenses). "Electrical Costs" means: (a) charges paid by Landlord
               for electricity; (b) costs reasonably incurred in connection with
               an energy

                                       10
<PAGE>   14

               management program for the Property; and (c) if and to the extent
               permitted by Law, a fee for the services provided by Landlord in
               connection with the selection of utility companies and the
               negotiation and administration of contracts for electricity,
               provided that such fee shall not exceed 50% of any savings
               obtained by Landlord. Electrical Costs shall be adjusted as
               follows: (i) amounts received by Landlord as reimbursement for
               above standard electrical consumption shall be deducted from
               Electrical Costs; (ii) the cost of electricity incurred to
               provide overtime HVAC to specific tenants (as reasonably
               estimated by Landlord) shall be deducted from Electrical Costs;
               and (iii) if Tenant is billed directly for the cost of building
               standard electricity to the Premises as a separate charge in
               addition to Base Rent, the cost of electricity to individual
               tenant spaces in the Building shall be deducted from Electrical
               Costs.

          6.   The amortized cost of capital improvements (as distinguished from
               replacement parts or components installed in the ordinary course
               of business) made to the Property which are: (a) performed
               primarily to reduce Expenses or otherwise improve the operating
               efficiency of the Property; or (b) required to comply with any
               Laws that are enacted, or first interpreted to apply to the
               Property, after the date of this Lease. The cost of such capital
               improvements shall be amortized by Landlord over the lesser of
               the Payback Period (defined below) or the useful life of the
               capital improvement as reasonably determined by Landlord (taking
               into account the number of hours during which such equipment is
               in use). The amortized cost of capital improvements may, at
               Landlord's option, include actual or imputed interest at the rate
               that Landlord would reasonably be required to pay to finance the
               cost of the capital improvement. "Payback Period" means the
               reasonably estimated period of time that it takes for the cost
               savings resulting from a capital improvement to equal the total
               cost of the capital improvement. Notwithstanding the foregoing,
               the portion of the annual amortized costs to be included in
               Expenses in any calendar year with respect to a capital
               improvement which is intended to reduce expenses or improve the
               operating efficiency of the Property or Building shall equal the
               lesser of: a) such annual amortized costs; and b) the projected
               annual amortized reduction in Expenses for that portion of the
               amortization period of the capital improvement which falls within
               the Term (based on the total cost savings for such period, as
               reasonably estimated by Landlord). Upon request by Tenant,
               Landlord shall provide Tenant with such information as Tenant
               reasonably requests concerning Landlord's projected cost savings,
               including an analysis of actual savings and the facts and
               assumptions that formed the basis of Landlord's projected
               savings.

          If Landlord incurs Expenses for the Property together with one or more
          other buildings or properties, whether pursuant to a reciprocal
          easement agreement, common area agreement or otherwise, the shared
          costs and expenses shall be equitably prorated and apportioned between
          the Property and the other buildings or properties. Expenses shall not
          include: (i) the cost of capital improvements (except as set forth
          above); (ii) depreciation; (iii) interest (except as provided above
          for the amortization of capital improvements); (iv) principal payments
          of mortgage and other non-operating debts of Landlord; (v) the cost of
          repairs or other work to the extent Landlord is reimbursed or entitled
          to reimbursement by insurance or condemnation proceeds; (vi) costs in
          connection with leasing space in the Building, including brokerage
          commissions; advertising and promotional expenditures and costs to
          prepare or perform work in tenant space in the Building (other than
          repairs and maintenance of the type described in Section IX.B.); (vii)
          lease concessions, including rental abatements and construction
          allowances, granted to specific tenants; (viii) costs incurred in
          connection with the sale, financing or refinancing of the Building;
          (ix) Taxes (defined in Section IV.E); (x) costs, expenses, fines,
          interest and penalties incurred due to the late payment of Taxes
          (defined in Section IV.E) or Expenses or due to the violation of Law;
          (xi) organizational expenses associated with the creation and
          operation of the entity which constitutes Landlord; (xii) any
          penalties or damages that Landlord pays to Tenant under this Lease or
          to other tenants in the Building under their respective leases; (xiii)
          expenses for any item or service not available to Tenant but provided
          to certain other tenant(s) in the Building; (xiv) expenses for any
          item or service which Tenant separately pays to Landlord; (xv) any
          cost incurred due to the adjudicated negligence or willful misconduct
          of the Landlord, its agents and employees; (xvi) rent payable under
          any ground lease; (xvii) reserves not expended in the calendar year
          for which Expenses are calculated; (xviii) expenses for the
          replacement of any item to the extent that the cost of replacing such
          item is covered by a valid and enforceable warranty or guaranty (as
          determined in Landlord's reasonable judgment); (xix) the initial costs
          incurred in connection with furnishing or decorating (including,
          without limitation, the purchase of artwork) the

                                       11
<PAGE>   15

          Common Areas (including, without limitation, the atrium); (xx) the
          cost of installing, operating and maintaining any specialty service
          such as a cafeteria/restaurant, retail store, sundry shop, newsstand
          or concession, provided that Expenses may include costs incurred in
          connection with the operation of a health club or similar amenities
          (other than conference facilities) commonly available at first class
          office buildings; (xxi) any costs in connection with the testing,
          monitoring or remediation of hazardous materials and/or substances
          existing at the Property as of the execution of this Lease; (xxii) the
          cost of correcting defects in the initial construction of the
          Building; (xxiii) insurance premiums to the extent any unusual tenant
          activity causes Landlord's existing insurance premiums to increase or
          requires the Landlord to purchase additional insurance, but only to
          the extent such additional cost can be identified by the insurer;
          (xxiv) amounts paid to Landlord or to subsidiaries or affiliates of
          Landlord for goods and services in the Building to the extent the same
          exceed the cost of such goods and services rendered on a competitive
          basis by unaffiliated third parties having comparable skill and
          experience; or (xxv) items or services which Tenant is required under
          this Lease to pay to a third party (e.g. separately metered
          utilities). If the Building is not at least 95% occupied during any
          calendar year or if Landlord is not supplying services to at least 95%
          of the total Rentable Square Footage of the Building at any time
          during a calendar year, Expenses shall, at Landlord's option, be
          determined as if the Building had been 95% occupied and Landlord had
          been supplying services to 95% of the Rentable Square Footage of the
          Building during that calendar year. If Tenant pays for its Pro Rata
          Share of Expenses based on increases over a "Expense Base Year" and
          Expenses for a calendar year are determined as provided in the prior
          sentence, Expenses for the Expense Base Year shall also be determined
          as if the Building had been 95% occupied and Landlord had been
          supplying services to 95% of the Rentable Square Footage of the
          Building. The extrapolation of Expenses under this Section shall be
          performed by appropriately adjusting the cost of those components of
          Expenses that are impacted by changes in the occupancy of the
          Building.

     D.   TAX EXCESS. Tenant shall pay Tenant's Pro Rata Share of the amount, if
          any, by which Taxes (defined in Section IV.E.) for each Fiscal Year
          during the Term exceed Taxes for the Tax Base Year (the "Tax Excess").
          If Taxes in any Fiscal Year decrease below the amount of Taxes for the
          Tax Base Year, Tenant's Pro Rata Share of Taxes for that Fiscal Year
          shall be $0. Landlord shall provide Tenant with a good faith estimate
          of the Tax Excess for each Fiscal Year during the Term. On or before
          the first day of each month, Tenant shall pay to Landlord a monthly
          installment equal to one-twelfth of Tenant's Pro Rata Share of
          Landlord's estimate of the Tax Excess. If Landlord determines that its
          good faith estimate of the Tax Excess was incorrect by a material
          amount, Landlord may provide Tenant with a revised estimate. After its
          receipt of the revised estimate, Tenant's monthly payments shall be
          based upon the revised estimate. If Landlord does not provide Tenant
          with an estimate of the Tax Excess by the start of each new Fiscal
          Year, Tenant shall continue to pay monthly installments based on the
          previous year's estimate(s) until Landlord provides Tenant with the
          new estimate. Upon delivery of the new estimate, an adjustment shall
          be made for any month for which Tenant paid monthly installments based
          on the previous year's estimate(s). Tenant shall pay Landlord the
          amount of any underpayment within 30 days after receipt of the new
          estimate. Any overpayment shall be refunded to Tenant within 30 days
          or credited against the next due future installment(s) of Additional
          Rent.

          As soon as is practical following the end of each Fiscal Year (but in
          no event later than 4 months following the end of such Fiscal Year),
          Landlord shall furnish Tenant with a statement of the actual Taxes and
          Tax Excess for the prior Fiscal Year. If the estimated Tax Excess for
          the prior Fiscal Year is more than the actual Tax Excess for the prior
          Fiscal Year, Landlord shall apply any overpayment by Tenant against
          Rent due or next becoming due, provided if the Term expires before the
          determination of the overpayment, Landlord shall refund, within 30
          days after the delivery of the statement, any overpayment to Tenant
          after first deducting the amount of any Rent due. If the estimated Tax
          Excess for the prior Fiscal Year is less than the actual Tax Excess
          for such prior year, Tenant shall pay Landlord, within 30 days after
          its receipt of the statement of Taxes, any underpayment for the prior
          Fiscal Year.

     E.   TAXES DEFINED. "Taxes" shall mean: (1) all real estate taxes and other
          assessments on the Building and/or Property, including, but not
          limited to, assessments for special improvement districts and building
          improvement districts, taxes and assessments levied in substitution or
          supplementation in whole or in part of any such taxes and assessments
          and the Property's share of any real estate taxes and assessments
          under any reciprocal easement agreement, common area agreement or
          similar agreement as

                                       12
<PAGE>   16

          to the Property; (2) all personal property taxes for property that is
          owned by Landlord and used in connection with the operation,
          maintenance and repair of the Property; and (3) all costs and fees
          incurred in connection with seeking reductions in any tax liabilities
          described in (1) and (2), including, without limitation, any costs
          incurred by Landlord for compliance, review and appeal of tax
          liabilities. Notwithstanding the foregoing, Landlord shall not incur
          any costs to contest tax liabilities unless Landlord believes that
          there is a reasonable likelihood that such contest will be successful
          in obtaining an abatement or reduction that will exceed the cost of
          such contest. Without limitation, Taxes shall not include any income,
          capital levy, franchise, capital stock, documentary stamp, excise,
          gift, estate or inheritance tax. If an assessment is payable in
          installments, Landlord shall elect to pay such Tax in installments
          over the longest period permitted by Law without penalty, and Taxes
          for the year shall include the amount of the installment and any
          interest due and payable during that year. Taxes for that year shall,
          at Landlord's election, include either the amount accrued, assessed or
          otherwise imposed for the year or the amount due and payable for that
          year, provided that Landlord's election shall be applied consistently
          throughout the Term. If a change in Taxes is obtained for any year of
          the Term during which Tenant paid Tenant's Pro Rata Share of any Tax
          Excess, then Taxes for that year will be retroactively adjusted and
          Landlord shall provide Tenant with a credit, if any, against Rent
          based on the adjustment, or if the Term shall have ended and Tenant
          shall have provided Landlord with its current address, refund the
          excess to Tenant within 30 days. Likewise, if a change is obtained for
          Taxes for the Tax Base Year, Taxes for the Tax Base Year shall be
          restated and the Tax Excess for all subsequent years shall be
          recomputed. Tenant shall pay Landlord the amount of Tenant's Pro Rata
          Share of any such increase in the Tax Excess within 30 days after
          Tenant's receipt of a statement from Landlord.

     F.   AUDIT RIGHTS. Tenant may, within 90 days after receiving Landlord's
          statement of Expenses or Taxes, give Landlord written notice ("Review
          Notice") that Tenant intends to review Landlord's records of the
          Expenses for that calendar year or Taxes for that Fiscal Year. Within
          a reasonable time after receipt of the Review Notice, Landlord shall
          make all pertinent records available for inspection that are
          reasonably necessary for Tenant to conduct its review. If any records
          are maintained at a location other than the office of the Building,
          Tenant may either inspect the records at such other location or pay
          for the reasonable cost of copying and shipping the records. If Tenant
          retains an agent to review Landlord's records, the agent must be a
          licensed CPA or with a licensed CPA firm. Tenant shall be solely
          responsible for all costs, expenses and fees incurred for the audit.
          Within 60 days after the records are made available to Tenant, Tenant
          shall have the right to give Landlord written notice (an "Objection
          Notice") stating in reasonable detail any objection to Landlord's
          statement of Expenses or Taxes for that year. If Tenant fails to give
          Landlord an Objection Notice within the 60 day period or fails to
          provide Landlord with a Review Notice within the 90 day period
          described above, Tenant shall be deemed to have approved Landlord's
          statement of Expenses or Taxes, as the case may be, and shall be
          barred from raising any claims regarding the Expenses or Taxes, as the
          case may be, for that year. If Tenant provides Landlord with a timely
          Objection Notice, Landlord and Tenant shall work together in good
          faith to resolve any issues raised in Tenant's Objection Notice. If
          Landlord and Tenant determine that Expenses for the calendar year or
          Taxes for the Fiscal Year are less than reported, Landlord shall
          provide Tenant with a credit against the next installment of Rent in
          the amount of the overpayment by Tenant, or, if no Rent is thereafter
          due, Landlord shall promptly pay such amount to Tenant. In addition,
          if Landlord and Tenant determine that Landlord's statement of Expenses
          or Taxes for the Building for the calendar year in question were
          overstated by five percent (5%) or more, Landlord shall be required to
          reimburse Tenant for any reasonable third party audit costs incurred
          by Tenant. Likewise, if Landlord and Tenant determine that Expenses
          for the calendar year or Taxes for the Fiscal Year are greater than
          reported, Tenant shall pay Landlord the amount of any underpayment
          within 30 days. The records obtained by Tenant shall be treated as
          confidential. In no event shall Tenant be permitted to examine
          Landlord's records or to dispute any statement of Expenses unless
          Tenant has paid and continues to pay all Rent when due.

V.   COMPLIANCE WITH LAWS; USE.

     A.   The Premises shall be used only for the Permitted Use and for no other
          use whatsoever. Tenant shall not use or permit the use of the Premises
          for any purpose which is illegal, dangerous to persons or property or
          which, in Landlord's reasonable opinion, unreasonably disturbs any
          other tenants of the Building or interferes with the operation of the
          Building. Tenant shall comply with all Laws, including the Americans
          with

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<PAGE>   17

          Disabilities Act ("ADA"), regarding (i) the operation of Tenant's
          business, (ii) the use of the Premises for purposes other than general
          office use, (iii) the condition of the Premises (other than conditions
          that are the responsibility of Landlord under Section IX.B.), and (iv)
          the configuration of the Premises. Notwithstanding the foregoing,
          Landlord shall be responsible for constructing the Landlord Work and
          Base Building Work in compliance with all Laws, including Title III of
          the Americans with Disabilities Act, provided that Tenant, not
          Landlord, shall be responsible for the correction of any violations
          that arise out of a failure by Tenant's architect to prepare the Plans
          (defined in the Work Letter attached hereto as EXHIBIT D) in strict
          compliance with all Laws, including the ADA. In addition, Landlord's
          obligation with respect to the Premises shall be limited to violations
          that arise out of the Landlord Work and/or the condition of the
          Premises prior to the installation of any furniture, equipment and
          other personal property of Tenant. Landlord shall have the right to
          contest any alleged violation in good faith, including, without
          limitation, the right to apply for and obtain a waiver or deferment of
          compliance, the right to assert any and all defenses allowed by law
          and the right to appeal any decisions, judgments or rulings to the
          fullest extent permitted by law. Landlord, after the exhaustion of any
          and all rights to appeal or contest, will make all repairs, additions,
          alterations or improvements necessary to comply with the terms of any
          final order or judgment. Tenant, within 10 days after receipt, shall
          provide Landlord with copies of any notices it receives regarding a
          violation or alleged violation of any Laws. Tenant shall reimburse and
          compensate Landlord for all expenditures made by, or damages or fines
          sustained or incurred by, Landlord due to any violations of Laws by
          Tenant or any Tenant Related Parties (as defined in Section XIV) with
          respect to the Premises. Tenant shall comply with the rules and
          regulations of the Building attached as EXHIBIT B and such other
          reasonable rules and regulations adopted by Landlord from time to
          time. Tenant shall also cause its agents, contractors, subcontractors,
          employees, customers, and subtenants to comply with all rules and
          regulations, including, without limitation, any rules and regulations
          established by Landlord in connection with any recycling program
          implemented by Landlord at the Building. Landlord shall not knowingly
          discriminate against Tenant in Landlord's enforcement of the rules and
          regulations and shall use reasonable efforts to uniformly enforce the
          rules and regulations against all tenants and occupants of the
          Building.

     B.   Nothing herein shall require Tenant to perform any alterations,
          additions or improvements which are necessary to comply with Laws with
          respect to the Common Areas, unless such requirement to comply relates
          to the Common Areas on any floor on which the Premises are located and
          arises directly out of the performance of work by Tenant in the
          Premises or Tenant's particular manner of use of the Premises for
          purposes other than general office use. In addition, nothing herein
          shall require Tenant to comply with Laws or requirements of public
          authorities which require the installation of new or additional
          mechanical, electrical, plumbing or fire/life safety systems on a
          Building-wide basis without reference to the particular use of Tenant
          or any Alterations (defined in Section IX.C. below) performed by
          Tenant subsequent to the Commencement Date ("Building-Wide Laws").
          Landlord will, at Landlord's expense (except to the extent properly
          included in Expenses), perform all acts required to comply with such
          Building-Wide Laws as the same affect the Premises and the Building.

VI.  SECURITY DEPOSIT.

     A.   The Security Deposit shall, at the option of Tenant, be in either the
          form of cash, a letter of credit or any combination thereof. The first
          fifty percent (50%) of the Security Deposit (i.e. $4,238,500.00) shall
          be delivered to Landlord by Tenant upon the execution of this Lease by
          Tenant. The remaining fifty percent (50%) of the Security Deposit
          shall be delivered to Landlord by Tenant during the performance of the
          Landlord Work in accordance with the following schedule: (i)
          $1,412,833.00 shall be delivered to Landlord on or before January 1,
          2000; (ii) $1,412,833.00 shall be delivered to Landlord on or before
          April 1, 2000; and (iii) $1,412,834.00 shall be delivered to Landlord
          on or before the Commencement Date. The Security Deposit shall be held
          by Landlord without liability for interest (unless required by Law) as
          security for the performance of Tenant's obligations; provided,
          however, that any portion of the cash Security Deposit in excess of
          the then current monthly installment of Base Rent shall be placed in a
          separate interest-bearing account with a FDIC-insured financial
          institution, with all interest to accrue to the benefit of Tenant,
          and, provided that no default shall have occurred and be continuing,
          to be paid or credited to Tenant annually. Landlord shall provide
          Tenant with the name of the institution and account number in which
          such cash portion of the Security Deposit is held. The Security
          Deposit is not an advance payment of Rent or a measure of Tenant's
          liability for damages. Landlord may, from time to time, without

                                       14
<PAGE>   18

          prejudice to any other remedy, use all or a portion of the Security
          Deposit to satisfy past due Rent or to cure any default by Tenant for
          which the cure period has expired. If Landlord uses the Security
          Deposit, Tenant shall on demand restore the Security Deposit to its
          original amount. Landlord shall return any unapplied portion of the
          Security Deposit to Tenant within 30 days after the later to occur of:
          (1) the date Tenant surrenders possession of the Premises to Landlord
          in accordance with this Lease; or (2) the Termination Date. In the
          event that Landlord reasonably believes that the estimated Expense
          Excess for the calendar year in which the Termination Date occurs or
          the estimated Tax Excess for the Fiscal Year in which the Termination
          Date occurs is less than the actual Expense Excess or Tax Excess for
          such calendar year or Fiscal Year, Landlord shall have the right to
          withhold the reasonably estimated shortfall from the Security Deposit
          to be returned to Tenant. In order to be entitled to withhold the
          reasonably estimated shortfall, Landlord shall be required to provide
          Tenant with documentation that is reasonably sufficient to demonstrate
          that a shortfall is likely to occur. Upon the determination of the
          actual Expense Excess or Tax Excess for the calendar year or Fiscal
          Year in question, Landlord shall perform a final reconciliation of
          such amounts in accordance with the terms of Article IV. If Tenant is
          entitled to a return of the Security Deposit, then to the extent such
          Security Deposit is in the form of a letter of credit, Landlord shall
          return the letter of credit accompanied by a letter from Landlord to
          the issuing bank advising such bank that Tenant has the right to
          surrender the letter of credit and that Landlord has no further
          interest therein. If Landlord transfers its interest in the Premises,
          Landlord shall assign the Security Deposit to the transferee and,
          following the assignment, Landlord shall have no further liability for
          the return of the Security Deposit. Notwithstanding the foregoing,
          Landlord shall not be released from liability with respect to the
          Security Deposit unless such assignee of the Security Deposit has
          agreed in writing to be liable for Landlord's obligations hereunder
          with respect to the Security Deposit. Landlord shall not be required
          to keep the Security Deposit separate from its other accounts.

     B.   If any portion of the Security Deposit is in the form of a letter of
          credit, such letter of credit shall (a) be in the form and substance
          of the sample letter of credit attached hereto as Exhibit I; (b) name
          Landlord as its beneficiary, (c) expire no earlier than thirty (30)
          days after the Termination Date (as the same may be extended), and (d)
          be drawn on Citibank, N.A., Silicon Valley East Bank or another
          FDIC-insured financial institution reasonably satisfactory to
          Landlord. If the initial term of the letter of credit will expire
          prior to thirty (30) days prior to the Termination Date, Tenant shall
          from time to time, as necessary, renew or replace the original and any
          subsequent letter of credit not less than thirty (30) days prior to
          its stated expiration date so that it will remain in full force and
          effect until thirty (30) days after the Termination Date. If Tenant
          fails to furnish such renewal or replacement at least thirty (30) days
          prior to the stated expiration date of the letter of credit then held
          by Landlord, Landlord may draw upon such letter of credit and hold the
          proceeds thereof (such proceeds to be segregated and held in an
          interest bearing account as described above) as a Security Deposit
          pursuant to the terms of this Article VI. Following any such draw upon
          the letter of credit, however, Tenant shall have the right to
          substitute a letter of credit meeting the requirements set forth
          herein (or other enumerated form of collateral) for the cash Security
          Deposit then held by Landlord. Any renewal of or replacement for the
          original or any subsequent letter of credit shall meet the
          requirements for the original letter of credit as set forth above.
          Provided that the letter of credit permits partial draws, Landlord
          shall not draw upon the letter of credit (or other form of Security
          Deposit) for an amount that is in excess of the amount necessary to
          cure Tenant's default under this Lease. If the letter of credit does
          not permit partial draws, Landlord shall hold any excess as a cash
          Security Deposit in accordance with the provisions of Subsection A.
          Tenant, from time to time, shall have the right to substitute a letter
          of credit for any portion of the Security Deposit that is held by
          Landlord in the form of cash. Tenant, from time to time, shall also
          have the right to substitute cash for any portion of the Security
          Deposit that is held by Landlord in the form of a letter of credit.

     C.   Notwithstanding anything herein to the contrary, provided Tenant is
          not in default under this Lease as of the third (3rd) anniversary of
          the Commencement Date (i.e. the expiration of the 3rd lease year), the
          amount of the Security Deposit shall reduce from $8,477,000.00 to
          $6,661,231.00 effective as of the 3rd anniversary of the Commencement
          Date. If the Security Deposit is provided by Tenant in the form of
          cash, Landlord shall return the reduced portion of the Security
          Deposit to Tenant within thirty (30) days following the 3rd
          anniversary of the Commencement Date. If the Security Deposit is
          provided in the form of a letter of credit, such reduction shall be
          accomplished by having Tenant provide Landlord with a substitute
          letter of credit in the reduced amount. If the Security Deposit is
          provided through a combination of cash and letter of

                                       15
<PAGE>   19

          credit, Tenant, by written notice to Landlord, shall advise Landlord
          as to the method that will be used to effectuate the reduction of the
          letter of credit.

     D.   In addition to the reduction of the Security Deposit described in
          Section VI.C. above, the amount of the Security Deposit shall be
          subject to further reduction effective as of the 4th, 5th, 6th and 7th
          anniversaries of the Commencement Date (each referred to as an
          "Anniversary Date") as follows:

          1) If Tenant reported a profit for the 4 consecutive quarters
          immediately preceding the applicable Anniversary Date, the amount of
          the Security Deposit shall reduce by $1,211,133.00 effective as of
          such Anniversary Date. Such reduction shall be accomplished in the
          manner referred to in Section VI.C. above, provided that Landlord
          shall not be required to refund any portion of the Security Deposit or
          to accept a substitute letter of credit unless and until Tenant has
          provided Landlord with audited financial statements evidencing that
          Tenant is entitled to a reduction of the Security Deposit in
          accordance with the terms hereof.

          2) If Tenant did not report a profit for the 4 consecutive quarters
          immediately preceding the applicable Anniversary Date but did report a
          profit for 3 quarters within such period, the amount of the Security
          Deposit shall reduce by $605,567.00 effective as such Anniversary
          Date. Such reduction shall be accomplished in the manner referred to
          in Section VI.C. above, provided that Landlord shall not be required
          to refund any portion of the Security Deposit or to accept a
          substitute letter of credit unless and until Tenant has provided
          Landlord with audited financial statements evidencing that Tenant is
          entitled to a reduction of the Security Deposit in accordance with the
          terms hereof.

          3) If Tenant is not entitled to a reduction of the Security Deposit
          under D.1. or D.2. above, Tenant shall not be entitled to a reduction
          of the Security Deposit with respect to the applicable Anniversary
          Date. Tenant shall, however, be entitled to a reduction of the
          Security Deposit with respect to any future Anniversary Dates where
          the conditions for a reduction have been satisfied. Notwithstanding
          anything herein to the contrary, in no event shall the Security
          Deposit be reduced below the sum of: (i) $1,816,699.00, plus (ii) the
          amount of any increase in the Security Deposit pursuant to Section
          VI.E. below.

     E.   In the event that Tenant leases additional square footage pursuant to
          its First Expansion Option, Second Expansion Option or Right of First
          Offer, the Security Deposit shall automatically increase by an amount
          determined in accordance with the following formula:

          (X divided by Y) x Z = increase in the Security Deposit

          X = the amount of the Security Deposit then held by Landlord
          Y = the then current rentable square footage of the Premises
          Z = the rentable square footage of the additional space

          For example, assume: (i) the Premises consists of 270,446 rentable
          square feet; (ii) the Security Deposit then held by Landlord is
          $6,661,231.00; and (iii) Tenant leases 20,000 rentable square feet
          that is in addition to the existing Premises. Under this example, the
          Security Deposit would be increased by $492,610.80. Tenant will be
          required to pay Landlord for the increase in the Security Deposit on
          or before the execution of the amendment adding the additional space
          to the Premises. Tenant shall have the right to determine whether the
          increase in the Security Deposit will be provided in the form of cash,
          letter of credit or a combination thereof.

VII. SERVICES TO BE FURNISHED BY LANDLORD.

     A.   Landlord agrees to furnish Tenant with the following services: (1)
          Water service for use in the lavatories on each floor on which the
          Premises are located; (2) Heat and air conditioning in season during
          Normal Business Hours in accordance with the specifications contained
          in the Base Building Scope attached hereto as Exhibit M, at such
          temperatures and in such amounts as are standard for comparable
          buildings or as required by governmental authority. Tenant, upon such
          advance notice as is reasonably required by Landlord, shall have the
          right to receive HVAC service during hours other than Normal Business
          Hours. Tenant shall pay Landlord a hourly charge for each hour of HVAC
          service that is requested and received by Tenant after Normal Business
          Hours. Such charge shall reflect the actual cost to Landlord of
          providing the HVAC service, as

                                       16
<PAGE>   20

          such cost is reasonably determined by Landlord; (3) Maintenance and
          repair of the Property as described in Section IX.B.; (4) Janitor
          service on Business Days in accordance with the specifications
          attached hereto as EXHIBIT N (or such reasonably comparable
          specifications as Landlord may designate from time to time). If
          Tenant's use, floor covering or other improvements require special
          services in excess of the standard services for the Building, and if
          such special services are requested by Tenant or otherwise required to
          keep the Premises in a reasonably clean condition, Landlord shall
          cause such special services to be furnished and Tenant shall pay the
          actual additional cost attributable to the special services to
          Landlord (without mark-up) or, at Landlord's election, to the provider
          of such special services; (5) Elevator service; (6) Electricity to the
          Premises for general office use, in accordance with and subject to the
          terms and conditions in Article X and EXHIBIT M; and (7) such other
          services as Landlord reasonably determines are necessary or
          appropriate for the Property.

     B.   Landlord's failure to furnish, or any interruption or termination of,
          services due to the application of Laws, the failure of any equipment,
          the performance of repairs, improvements or alterations, or the
          occurrence of any event or cause beyond the reasonable control of
          Landlord (a "Service Failure") shall not render Landlord liable to
          Tenant, constitute a constructive eviction of Tenant, give rise to an
          abatement of Rent, nor relieve Tenant from the obligation to fulfill
          any covenant or agreement. However, if the Premises, or a material
          portion of the Premises, is made untenantable for a period in excess
          of 3 consecutive Business Days as a result of the Service Failure,
          then Tenant, as its sole remedy, shall be entitled to receive an
          abatement of Rent payable hereunder during the period beginning on the
          4th consecutive Business Day of the Service Failure and ending on the
          day the service has been restored. If the entire Premises has not been
          rendered untenantable by the Service Failure, the amount of abatement
          that Tenant is entitled to receive shall be prorated based upon the
          percentage of the Premises rendered untenantable and not used by
          Tenant. In no event, however, shall Landlord be liable to Tenant for
          any loss or damage, including the theft of Tenant's Property (defined
          in Article XV), arising out of or in connection with the failure of
          any security services, personnel or equipment. Landlord agrees to use
          reasonable efforts to restore any interruption or termination of
          services.

VIII. LEASEHOLD IMPROVEMENTS.

     A.   Except for Tenant's Property (as defined in Section XV), all
          improvements to the Premises (collectively, "Leasehold Improvements")
          shall be owned by Landlord and shall remain upon the Premises without
          compensation to Tenant. However, Landlord, by written notice to Tenant
          within 180 days prior to the Termination Date, may require Tenant to
          remove, at Tenant's expense: (1) Cable (defined in Section IX.A)
          installed by or for the exclusive benefit of Tenant and located in the
          Premises or other portions of the Building; and (2) subject to Section
          VIII.B. below, any Leasehold Improvements that are performed by or for
          the benefit of Tenant and, in Landlord's reasonable judgment, are of a
          nature that would require removal and repair costs that are materially
          in excess of the removal and repair costs associated with standard
          office improvements (collectively referred to as "Required
          Removables"). Without limitation, it is agreed that Required
          Removables include internal stairways, raised floors, personal baths
          and showers, vaults, rolling file systems and structural alterations
          and modifications of any type. The Required Removables designated by
          Landlord shall be removed by Tenant before the Termination Date,
          provided that upon prior written notice to Landlord, Tenant may remain
          in the Premises for up to 5 days after the Termination Date for the
          sole purpose of removing the Required Removables. Tenant's possession
          of the Premises shall be subject to all of the terms and conditions of
          this Lease, including the obligation to pay Rent on a per diem basis
          at the rate in effect for the last month of the Term. Tenant shall
          repair damage caused by the installation or removal of Required
          Removables. If Tenant fails to remove any Required Removables or
          perform related repairs in a timely manner, Landlord, at Tenant's
          expense, may remove and dispose of the Required Removables and perform
          the required repairs. Tenant, within 30 days after receipt of an
          invoice, shall reimburse Landlord for the reasonable costs incurred by
          Landlord.

     B.   Notwithstanding Section VIII.A. to the contrary and except as provided
          below with respect to the Landlord Work, Tenant, at the time it
          requests approval for a proposed Alteration (defined in Section IX.C),
          may request in writing that Landlord advise Tenant whether the
          Alteration or any portion of the Alteration will be designated as a
          Required Removable. Within 10 days after receipt of Tenant's request,
          Landlord shall advise Tenant in writing as to which portions of the
          Alteration, if any, will be considered to be Required Removables.

                                       17
<PAGE>   21

          With respect to the Landlord Work, Landlord shall notify Tenant in
          writing of any Required Removables within 5 Business Days after the
          date on which Landlord approves Tenant's Design Development Plans
          (defined in the Work Letter attached hereto as EXHIBIT D); provided
          that any internal staircase shall be considered to be a Required
          Removable regardless of whether Landlord designates the same as a
          Required Removable in a written notice to Tenant and regardless of
          whether Landlord provides Tenant with 180 days prior notice of removal
          in accordance with Section VIII.A. above. Except with respect to any
          internal staircase, Landlord shall have no right to require the
          removal of any Alterations or Landlord Work not so identified as
          Required Removables pursuant to this Subsection VIII.B.

IX.  REPAIRS AND ALTERATIONS.

     A.   TENANT'S REPAIR OBLIGATIONS. Tenant shall, at its sole cost and
          expense, promptly perform all maintenance and repairs to the Premises
          that are not Landlord's express responsibility under this Lease, and
          shall keep the Premises in good condition and repair, reasonable wear
          and tear excepted, and subject to the provisions of Section XVII
          (Casualty Damage) and XVIII (Condemnation) of this Lease. Tenant's
          repair obligations include, without limitation, repairs to: (1) floor
          covering; (2) interior partitions; (3) doors; (4) the interior side of
          demising walls; (5) electronic, phone and data cabling and related
          equipment (collectively, "Cable") that is installed by or for the
          exclusive benefit of Tenant and located in the Premises or other
          portions of the Building; (6) supplemental air conditioning units,
          private showers and kitchens, including hot water heaters, plumbing,
          and similar facilities serving Tenant exclusively; and (7) Alterations
          performed by contractors retained by Tenant, including related HVAC
          balancing. All work shall be performed in accordance with the rules
          and procedures described in Section IX.C. below. If Tenant fails to
          make any repairs to the Premises for more than 30 days after notice
          from Landlord (although notice shall not be required if there is an
          emergency) (which 30-day period shall be extended for such additional
          time as shall be reasonably necessary under the circumstances provided
          that Tenant commences cure within such 30-day period and is diligently
          prosecuting completion of the same), Landlord may make the repairs,
          and Tenant shall pay the reasonable cost of the repairs to Landlord
          within 30 days after receipt of an invoice, together with an
          administrative charge in an amount equal to 10% of the cost of the
          repairs.

     B.   LANDLORD'S REPAIR OBLIGATIONS. Landlord shall keep and maintain in
          good repair and working order and make repairs to and perform
          maintenance upon: (1) structural elements of the Building; (2)
          mechanical (including HVAC), electrical, plumbing and fire/life safety
          systems serving the Building in general; (3) Common Areas; (4) the
          roof of the Building; (5) exterior windows of the Building; and (6)
          elevators serving the Building. Landlord shall promptly make repairs
          (considering the nature and urgency of the repair) for which Landlord
          is responsible. In addition, Landlord may elect, at the expense of
          Tenant, to repair any damage or injury to the Building caused by
          moving property of Tenant in or out of the Building, or by
          installation or removal of furniture or other property, or by misuse
          by, neglect or improper conduct of Tenant or any Tenant Related
          Parties (defined in Section XIV.B. herein).

     C.   ALTERATIONS. Tenant shall not make alterations, additions or
          improvements to the Premises or install any Cable in the Premises or
          other portions of the Building (collectively referred to as
          "Alterations") without first obtaining the written consent of Landlord
          in each instance, which consent shall not be unreasonably withheld or
          delayed. However, Landlord's consent shall not be required for any
          Alteration that satisfies all of the following criteria (a
          "Non-Material Alteration"): (1) with respect to the portion of the
          Premises located on the first floor, is not visible from the exterior
          of the Premises or Building; (2) will not affect the systems or
          structure of the Building; and (3) does not legally require the
          issuance of a building permit. Without limiting the foregoing, it is
          agreed that Tenant shall have the right to install voice and data
          cabling in the Premises without the consent of Landlord; provided that
          if Tenant requires access to the Building telecommunication closets,
          electrical closets or similar areas, the manner in which Tenant
          accesses such areas and connects its equipment to the Building
          equipment shall be subject to Landlord's approval, which approval
          shall not be unreasonably withheld or delayed. However, even though
          consent is not required, the performance of Non-Material Alterations,
          unless otherwise indicated herein, shall be subject to all the other
          provisions of this Section IX.C. Prior to starting work, Tenant shall
          furnish Landlord with plans and specifications reasonably acceptable
          to Landlord (except for Non-Material Alterations); names of
          contractors reasonably acceptable to Landlord (provided that

                                       18
<PAGE>   22

          Landlord may designate specific contractors with respect to Building
          systems, provided further, that the rates charged by such contractors
          are competitive with market rates); copies of contracts; necessary
          permits and approvals; evidence of contractor's and subcontractor's
          insurance in amounts reasonably required by Landlord; and any security
          for performance that is reasonably required by Landlord. Changes to
          the plans and specifications must also be submitted to Landlord for
          its approval. Alterations shall be constructed in a good and
          workmanlike manner using materials of a quality that is at least equal
          to the quality designated by Landlord as the minimum standard for the
          Building. Landlord may designate reasonable rules, regulations and
          procedures for the performance of work in the Building and, to the
          extent reasonably necessary to avoid disruption to the occupants of
          the Building, shall have the right to designate the time when
          Alterations may be performed. Except with respect to Non-Material
          Alterations, Tenant shall reimburse Landlord within 30 days after
          receipt of an invoice for sums paid by Landlord for third party
          examination of Tenant's plans for Alterations. In addition, within 30
          days after receipt of an invoice from Landlord, Tenant shall pay
          Landlord a fee for Landlord's oversight and coordination of any
          Alterations (other than Non-Material Alterations) equal to 5% of the
          cost of the Alterations. Upon completion, Tenant shall furnish
          "as-built" plans (except for Non-Material Alterations), completion
          affidavits, full and final waivers of lien and receipted bills
          covering all labor and materials. Tenant shall assure Landlord that
          the Alterations comply with all insurance requirements and Laws.
          Landlord's approval of an Alteration shall not be a representation by
          Landlord that the Alteration complies with applicable Laws or will be
          adequate for Tenant's use. Tenant shall pay, as an additional charge,
          the entire increase in real estate taxes on the Building which shall,
          at any time prior to or after the Commencement Date, result from or be
          attributable to any Alteration made by or for the account of Tenant in
          excess of the building standard improvements for the Building.

X.   USE OF ELECTRICAL SERVICES BY TENANT.

     A.   All electricity used by Tenant in the Premises shall be paid for by
          Tenant as Additional Rent within thirty (30) days after receipt of an
          invoice from Landlord. Tenant's electricity charge for each month
          shall be an amount computed by applying the kilowatt hours shown on
          the submeter in the Premises for the billing period in question to
          Landlord's Monthly Cost Rate, as such term is hereinafter defined. As
          used herein, the term "Landlord's Monthly Cost Rate" shall mean the
          per kilowatt hour charge for the relevant billing period (carried to
          six decimal places) determined by dividing the total amount charged
          for electrical service to the Building by the utility provider(s)
          servicing the Building for the relevant monthly billing period by the
          total kilowatt hours consumed by the Building for such monthly period
          carried to six decimal places. If any tax is imposed on Landlord's
          receipt from the sale or resale of electric energy by any federal,
          state or municipal authority, Tenant covenants and agrees that, where
          permitted by law, Tenant's pro rata share of such taxes based upon
          kilowatt hours consumed with respect to the Premises shall be passed
          on to, and included in the bill of, and paid by, Tenant to Landlord.
          Landlord, as part of the Landlord Work, shall install any necessary
          sub-meters (as well as any electrical panels, transformers, bus duct
          plug and related equipment) in the Premises at Tenant's sole cost and
          expense. In the event Tenant shall consume (or request that it be
          allowed to consume) electrical service in excess of the tenant
          electrical design load specifications that are included within the
          Base Building Scope (attached hereto as EXHIBIT M), Landlord shall
          cooperate with Tenant to provide such excess usage, which cooperation
          may be conditioned upon such conditions as Landlord reasonably
          determines to be necessary (including the installation of utility
          service upgrades, submeters, air handlers or cooling units), and all
          such additional usage (to the extent permitted by Law), installation
          and maintenance thereof shall be paid for by Tenant as Additional
          Rent.

     B.   Electrical service to the Premises may be furnished by one or more
          companies providing electrical generation, transmission and
          distribution services, and the cost of electricity may consist of
          several different components or separate charges for such services,
          such as generation, distribution and stranded cost charges. Landlord
          shall have the exclusive right to select any company providing
          electrical service to the Premises, to aggregate the electrical
          service for the Property and Premises with other buildings, to
          purchase electricity through a broker and/or buyers group and to
          change the providers and manner of purchasing electricity. Landlord
          shall be entitled to receive a fee (if permitted by Law) for the
          selection of utility companies and the negotiation and administration
          of contracts for electricity, provided that the amount of such fee
          shall not exceed 50% of any identifiable savings obtained by Landlord
          when compared to the

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<PAGE>   23

          electricity rates that would have been applicable to the Premises if
          Landlord had not provided such service(s).

XI.  ENTRY BY LANDLORD.

     Landlord, its agents, contractors and representatives may enter the
Premises to inspect or show the Premises, to clean and make repairs, alterations
or additions to the Premises, and to conduct or facilitate repairs, alterations
or additions to any portion of the Building, including other tenants' premises.
Except in emergencies or to provide janitorial and other Building services after
Normal Business Hours, Landlord shall provide Tenant with reasonable prior
notice of entry into the Premises, which may be given orally. If reasonably
necessary for the protection and safety of Tenant and its employees, Landlord
shall have the right to temporarily close all or a portion of the Premises to
perform repairs, alterations and additions. However, except in emergencies,
Landlord will not close the Premises if the work can reasonably be completed on
weekends and after Normal Business Hours. Entry by Landlord shall not constitute
constructive eviction or entitle Tenant to an abatement or reduction of Rent.
Landlord shall use reasonable efforts in the exercise of its rights hereunder
not to interfere with Tenant's use of the Premises, and in the event that
Landlord temporarily closes all or a part of the Premises, Landlord shall use
due diligence to complete any work in the Premises and to re-open the closed
portion of the Premises as soon as possible. Notwithstanding the foregoing,
unless the closure of all or a part of the Premises shall be due to Tenant's
default under the terms of this Lease, if the Premises, or a material portion
thereof, are closed by Landlord to perform repairs alterations or additions for
a period in excess of 3 consecutive Business Days, then Tenant, as its sole
remedy, shall be entitled to receive an abatement of Rent payable hereunder
during the period beginning on the 4th consecutive Business Day of such closure
and ending on the day such closed portion of the Premises has been re-opened. If
less than entire Premises have been so closed, the amount of abatement that
Tenant is entitled to receive shall be prorated based upon the percentage of the
Premises unavailable for Tenant's use.

XII. ASSIGNMENT AND SUBLETTING.

     A.   Except in connection with a Permitted Transfer (defined in Section
          XII.E. below), Tenant shall not assign, sublease, transfer or encumber
          any interest in this Lease or allow any third party to use any portion
          of the Premises (collectively or individually, a "Transfer") without
          the prior written consent of Landlord, which consent shall not be
          unreasonably withheld, conditioned or delayed if Landlord does not
          elect to exercise its recapture rights under Section XII.B below.
          Without limitation, it is agreed that Landlord's consent shall not be
          considered unreasonably withheld if: (1) the proposed transferee's net
          worth is less than $43,000,000.00, provided that such criteria shall
          only be applicable to an assignee of this Lease, and shall not be
          applicable to a subtenant or other occupant of the Premises; (2) the
          proposed transferee's business is not suitable for the Building
          considering the Building's prestige, (3) if the proposed transferee
          intends to use all or a portion of the Premises for any retail or
          quasi-retail use (e.g. an executive suites or temporary help business)
          or for the general office use of a company other than a software or
          computer company, such use would result in a violation of another
          tenant's rights; provided, however, the parties agree that this
          condition shall not be construed to imply that Tenant or any
          transferee shall have the right to use the Premises for a retail or
          quasi-retail use; (4) the proposed transferee is a governmental agency
          or occupant of the Building; provided that Landlord will not withhold
          its consent solely because the proposed subtenant or assignee is an
          occupant of the Building if Landlord does not have space available for
          lease in the Building that is comparable (based upon the available
          term and size of the available space) to the space Tenant desires to
          sublet or assign; (5) Tenant is in default after the expiration of the
          notice and cure periods in this Lease; (6) any portion of the Building
          or Premises would likely become subject to additional or different
          Laws as a consequence of the proposed Transfer; provided that Landlord
          will not refuse consent solely for such reasons if Tenant agrees to
          pay for 100% of any related legal compliance costs, including any
          costs with respect to any period after the Termination Date; or (7)
          Landlord has commenced negotiations with the proposed transferee for
          other space in the Building which is comparable in terms of available
          term and size to the space that Tenant proposes to transfer. For
          purposes hereof, the term "commenced negotiations" shall mean that
          Landlord, within six (6) months prior to the date on which Tenant
          requests consent to a Transfer, has shown such proposed transferee
          space in the Building and has submitted a written proposal to such
          proposed transferee. Upon written request of Tenant from time to time,
          Landlord shall advise Tenant in writing as to whether Landlord has
          granted any exclusive or other restrictive use rights that would allow
          Landlord to refuse consent to a proposed transferee in

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<PAGE>   24

          accordance with subsection XII.A.(3) above. Such list of rights shall
          be binding on Landlord for a period of 6 months after delivery to
          Tenant and, during such 6 month period, Landlord shall not be entitled
          to refuse consent to a proposed Transfer based solely upon a violation
          of any exclusive or restrictive use right that is not included on such
          list. Tenant shall not be entitled to receive monetary damages based
          upon a claim that Landlord unreasonably withheld its consent to a
          proposed Transfer and Tenant's sole remedy shall be an action to
          enforce any such provision through specific performance or declaratory
          judgment. Any attempted Transfer in violation of this Article shall,
          at Landlord's option, be void. Consent by Landlord to one or more
          Transfer(s) shall not operate as a waiver of Landlord's rights to
          approve any subsequent Transfers. In no event shall any Transfer or
          Permitted Transfer (hereinafter defined) release or relieve Tenant
          from any obligation under this Lease.

     B.   As part of its request for Landlord's consent to a Transfer, Tenant
          shall provide Landlord with financial statements for the proposed
          transferee, a complete copy of the proposed assignment, sublease and
          other contractual documents and such other information as Landlord may
          reasonably request. Landlord shall, by written notice to Tenant within
          10 Business Days of its receipt of the required information and
          documentation, either: (1) consent to the Transfer by the execution of
          a consent agreement in a form reasonably designated by Landlord or
          reasonably refuse to consent to the Transfer in writing; or (2)
          recapture the space that Tenant desires to Transfer; which recapture
          shall be effective only with respect to the portion of the Term
          covered by the proposed Transfer; provided if there would be less than
          six months remaining in the Term following the expiration of the
          proposed Transfer, Landlord shall be entitled to recapture the space
          in question for the entire remaining portion of the Term.
          Notwithstanding the foregoing, Landlord shall not have the right to:
          (a) recapture any portion of the Premises that is being transferred
          pursuant to a Permitted Transfer (hereinafter defined); or (b)
          recapture a portion of the Premises in connection with a proposed
          sublease for space in One Riverside Center or Two Riverside Center if
          the space proposed for sublease does not include at least 1 full floor
          of space in One Riverside Center or Two Riverside Center. If a
          proposed sublease includes more than 1 full floor, Landlord shall only
          have the right to recapture space in full floor increments. For
          example, if Tenant proposes to enter into a sublease for space that
          includes 1 full floor plus 10,000 square feet on another floor,
          Landlord shall have the right to recapture the full floor that Tenant
          proposes to sublet, but not the 10,000 square foot portion of the
          space that is proposed for sublease. Any such recapture shall be
          effective on the proposed effective date of the Transfer for which
          Tenant requested consent. Tenant shall pay Landlord a review fee of
          $750.00 for Landlord's review of any Permitted Transfer or requested
          Transfer, provided if Landlord's actual reasonable costs and expenses
          (including reasonable attorney's fees) exceed $750.00, Tenant shall
          reimburse Landlord for its actual reasonable costs and expenses in
          lieu of a fixed review fee.

     C.   Tenant shall pay Landlord 50% of all rent and other consideration
          which Tenant receives as a result of a Transfer that is in excess of
          the Rent payable to Landlord for the portion of the Premises and Term
          covered by the Transfer. Tenant shall pay Landlord for Landlord's
          share of any excess within 30 days after Tenant's receipt of such
          excess consideration. Tenant may deduct from the excess all reasonable
          and customary expenses directly incurred by Tenant attributable to the
          Transfer including Landlord's review fee, brokerage fees, legal fees
          and construction costs. If Tenant is in Monetary Default (defined in
          Section XIX.A. below), Landlord may require that all sublease payments
          be made directly to Landlord, in which case Tenant shall receive a
          credit against Rent in the amount of any payments received (less
          Landlord's share of any excess).

          Landlord and Tenant acknowledge that, during the first fifteen (15)
          months of the Term (the "Reduced Rent Period"), Tenant, in accordance
          with Section I.D., pays Base Rent based on less than the entire
          rentable square footage of the Premises. The portion of the Premises
          for which Tenant is not required to pay Base Rent during the Reduced
          Rent Period is referred to as the "Reduced Rent Premises". Subject to
          adjustment in accordance with Section I.C., during months 1 - 6 of the
          Term, the Reduced Rent Premises shall consist of 76,419 rentable
          square feet and, during months 7 - 15 of the Term, the Reduced Rent
          Premises shall consist of 38,209 rentable square feet. Any space in
          the Premises assigned or sublet by Tenant during the first 15 months
          of the Term (regardless of whether such space in located in the One
          Riverside Center Premises or the Two Riverside Center Premises) shall
          first be attributable to the Reduced Rent Premises, and if the area of
          the space so assigned or sublet exceeds the Reduced Rent Premises,
          then to the Premises. Notwithstanding the first paragraph of Section
          XII.C. above to the contrary, Landlord shall not have the right to
          participate in sublease profits in connection

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<PAGE>   25

          with any Reduced Rent Premises during the Reduced Rent Period.
          Landlord shall, however, have the right to participate is sublease
          profits with respect to (i) any portion of the Premises that is not,
          from time to time, considered to be Reduced Rent Premises, and (ii)
          any portion of the Term that does not fall within the Reduced Rent
          Period. For example, if Tenant sublets 100,000 rentable square feet
          for the first 24 months of the Term: (iii) during months 1-6, Landlord
          shall be entitled to 50% of any sublet profits with respect to 23,581
          rentable square feet of such sublet space; (iv) during months 7- 15,
          Landlord shall be entitled to 50% of any sublet profits with respect
          to 61,791 rentable square feet of such sublet space; and (v) beginning
          with the first day of month 16 of the Term, Landlord shall be entitled
          to 50% of any sublet profits with respect to the entire sublet
          premises. Notwithstanding anything in Section XII.B. above to the
          contrary, Landlord shall not be entitled to recapture any portion of
          the Reduced Rent Premises that is sublet for a term beginning at any
          time during the Reduced Rent Period.

     D.   Except as provided below with respect to a Permitted Transfer, if
          Tenant is a corporation, limited liability company, partnership, or
          similar entity, and if the entity which owns or controls a majority of
          the voting shares/rights at any time changes for any reason (including
          but not limited to a merger, consolidation or reorganization), such
          change of ownership or control shall constitute a Transfer. The
          foregoing shall not apply so long as Tenant is an entity whose
          outstanding stock is listed on a recognized security exchange, or if
          at least 80% of its voting stock is owned by another entity, the
          voting stock of which is so listed.

     E.   Tenant may assign its entire interest under this Lease or sublet the
          Premises or any portion thereof to a wholly owned corporation,
          partnership or other legal entity or affiliate, subsidiary or parent
          of Tenant or to any successor to Tenant by purchase, merger,
          consolidation or reorganization (hereinafter, collectively, referred
          to as "Permitted Transfer") without the consent of Landlord, provided:
          (i) Tenant is not in default under this Lease beyond notice and
          applicable cure periods; (ii) if such proposed transferee is a
          successor to Tenant by purchase, merger, consolidation or
          reorganization, the continuing or surviving entity shall own all or
          substantially all of the assets of Tenant; (iii) such proposed
          transferee operates the business in the Premises for the Permitted Use
          and no other purpose; and (iv) in no event shall any Permitted
          Transfer release or relieve Tenant from any of its obligations under
          this Lease. In addition, if the proposed transferee is a successor to
          Tenant by purchase, merger, consolidation or reorganization and the
          continuing or surviving entity does not have a net worth which is at
          least equal to the lesser of Thirty-Two Million Two Hundred Fifty
          Thousand Dollars ($32,250,000.00) or the net worth of Tenant
          immediately prior to such purchase, merger, consolidation or
          reorganization, then Tenant shall be required to increase the amount
          of the Security Deposit by an amount determined in accordance with the
          following formula:

          A x B = Increase in Security Deposit

          A = the percentage decrease in Tenant's net worth as calculated by
          comparing (1) the lesser of $32,250,000.00 and Tenant's net worth
          immediately prior to the purchase, merger, consolidation or
          reorganization to (2) Tenant's net worth immediately following the
          purchase, merger, consolidation or reorganization

          B = The Security Deposit in effect on the closing date of the
          purchase, merger, consolidation or reorganization

          For example: If Tenant's net worth decreases by 20% as a result of a
          purchase, merger, consolidation or reorganization, the amount of the
          Security Deposit shall be increased by 20%. In no event, however,
          shall the Security Deposit be increased to be more than $12,111,000
          during the first 3 lease years of the Term or to be more than
          $8,478,000 at any time after the first 3 lease years of the Term;
          provided that such maximum amounts shall be increased on a dollar for
          dollar basis by any increase in the Security Deposit under Section
          VI.D above. Tenant shall give Landlord written notice at least thirty
          (30) days prior to the effective date of such Permitted Transfer;
          provided that if the Permitted Transfer is being treated as
          confidential by Tenant, Tenant shall provide Landlord with written
          notice within thirty (30) days after the first to occur of the closing
          date of the Permitted Transfer and the date that the occurrence or
          proposed occurrence of the Permitted Transfer becomes public
          knowledge. As used herein: (a) "parent" shall mean a company which
          owns a majority of Tenant's voting equity; (b) "subsidiary" shall mean
          an entity wholly owned by Tenant or at least fifty-one percent (51%)
          of whose voting equity is owned by Tenant; (c) "affiliate" shall mean
          an entity controlled, controlling or

                                       22
<PAGE>   26

          under common control with Tenant; and (d) "net worth" shall mean
          Tenant's total assets minus Tenant's total liabilities calculated at
          the period of time in question. Notwithstanding the provisions of
          subsection C, above, any Permitted Transfer shall be deemed to be of
          non-Reduced Rent Premises, and if the area of such space so assigned
          or sublet exceeds the non-Reduced Rent Premises, then to the Reduced
          Rent Premises.

XIII. LIENS.

     Tenant shall not permit mechanic's or other liens to be placed upon the
Property, Premises or Tenant's leasehold interest in connection with any work or
service done or purportedly done by or for benefit of Tenant. If a lien is so
placed, Tenant shall, within 10 days of notice from Landlord of the filing of
the lien, fully discharge the lien by settling the claim which resulted in the
lien or by bonding or insuring over the lien in the manner prescribed by the
applicable lien Law. If Tenant fails to discharge the lien or to bond over or
insure the same, then, in addition to any other right or remedy of Landlord,
Landlord may bond or insure over the lien or otherwise discharge the lien.
Tenant shall reimburse Landlord for any amount paid by Landlord to bond or
insure over the lien or discharge the lien, including, without limitation,
reasonable attorneys' fees (if and to the extent permitted by Law) within 30
days after receipt of an invoice from Landlord.

XIV. INDEMNITY AND WAIVER OF CLAIMS.

     A.   Except to the extent caused by the negligence or willful misconduct of
          Landlord or any Landlord Related Parties (defined below), Tenant shall
          indemnify, defend and hold Landlord, its trustees, members,
          principals, beneficiaries, partners, officers, directors, employees,
          Mortgagee(s) (defined in Article XXVI) and agents ("Landlord Related
          Parties") harmless against and from all liabilities, obligations,
          damages, penalties, claims, actions, costs, charges and expenses,
          including, without limitation, reasonable attorneys' fees and other
          professional fees (if and to the extent permitted by Law), which may
          be imposed upon, incurred by or asserted against Landlord or any of
          the Landlord Related Parties and to the extent caused by and arising
          out of or in connection with any acts or omissions (including
          violations of Law) of Tenant, the Tenant Related Parties (defined
          below) or any of Tenant's transferees, contractors or licensees.

     B.   Except to the extent caused by the negligence or willful misconduct of
          Tenant or any Tenant Related Parties (defined below), Landlord shall
          indemnify, defend and hold Tenant, its trustees, members, principals,
          beneficiaries, partners, officers, directors, employees and agents
          ("Tenant Related Parties") harmless against and from all liabilities,
          obligations, damages, penalties, claims, actions, costs, charges and
          expenses, including, without limitation, reasonable attorneys' fees
          and other professional fees (if and to the extent permitted by Law),
          which may be imposed upon, incurred by or asserted against Tenant or
          any of the Tenant Related Parties and to the extent caused by and
          arising out of or in connection with the acts or omissions (including
          violations of Law) of Landlord, the Landlord Related Parties or any of
          Landlord's contractors.

     C.   Landlord and the Landlord Related Parties shall not be liable for, and
          Tenant waives, all claims for loss or damage to Tenant's business or
          loss, theft or damage to Tenant's Property (defined in Article XV) or
          the property of any person claiming by, through or under Tenant
          resulting from: (1) wind or weather; (2) the failure of any sprinkler,
          heating or air-conditioning equipment, any electric wiring or any gas,
          water or steam pipes; (3) the backing up of any sewer pipe or
          downspout; (4) the bursting, leaking or running of any tank, water
          closet, drain or other pipe; (5) water, snow or ice upon or coming
          through the roof, skylight, stairs, doorways, windows, walks or any
          other place upon or near the Building; (6) any act or omission of any
          party other than Landlord or Landlord Related Parties; and (7) any
          causes not reasonably within the control of Landlord. Tenant shall
          insure itself against such losses under Article XV below.

XV.  INSURANCE.

     Tenant shall carry and maintain the following insurance ("Tenant's
Insurance"), at its sole cost and expense: (1) Commercial General Liability
Insurance applicable to the Premises and its appurtenances providing, on an
occurrence basis, a minimum combined single limit of $2,000,000.00; (2) All Risk
Property/Business Interruption Insurance, including flood and earthquake,
written at replacement cost value and with a replacement cost endorsement
covering all of Tenant's trade fixtures, equipment, furniture and other personal
property within

                                       23
<PAGE>   27

the Premises ("Tenant's Property"); (3) Workers' Compensation Insurance as
required by the state in which the Premises is located and in amounts as may be
required by applicable statute; and (4) Employers Liability Coverage of at least
$1,000,000.00 per occurrence. Any company writing any of Tenant's Insurance
shall have an A.M. Best rating of not less than A-VIII. All Commercial General
Liability Insurance policies shall name Tenant as a named insured and Landlord
(or any successor), Equity Office Properties Trust, a Maryland real estate
investment trust, EOP Operating Limited Partnership, a Delaware limited
partnership, Beacon Property Management Corporation, a Delaware corporation and
their respective members, principals, beneficiaries, partners, officers,
directors, employees, and agents, and other designees of Landlord as the
interest of such designees shall appear, as additional insureds. All policies of
Tenant's Insurance shall contain endorsements that the insurer(s) shall give
Landlord and its designees at least 30 days' advance written notice of any
change, cancellation, termination or lapse of insurance. Tenant shall provide
Landlord with a certificate of insurance evidencing Tenant's Insurance prior to
the earlier to occur of the Commencement Date or the date Tenant is provided
with possession of the Premises for any reason, and upon renewals at least 15
days prior to the expiration of the insurance coverage. Landlord shall maintain
so called All Risk property insurance on the Building at replacement cost value,
as reasonably estimated by Landlord. Except as specifically provided to the
contrary, the limits of either party's insurance shall not limit such party's
liability under this Lease.

XVI. SUBROGATION.

     Notwithstanding anything in this Lease to the contrary, Landlord and Tenant
hereby waive and shall cause their respective insurance carriers to waive any
and all rights of recovery, claim, action or causes of action against the other
and their respective trustees, principals, beneficiaries, partners, officers,
directors, agents, and employees, for any loss or damage that may occur to
Landlord or Tenant or any party claiming by, through or under Landlord or
Tenant, as the case may be, with respect to Tenant's Property, the Building, the
Premises, any additions or improvements to the Building or Premises, or any
contents thereof, including all rights of recovery, claims, actions or causes of
action arising out of the negligence of Landlord or any Landlord Related Parties
or the negligence of Tenant or any Tenant Related Parties, which loss or damage
is (or would have been, had the insurance required by this Lease been carried)
covered by insurance.

XVII. CASUALTY DAMAGE.

     A.   If all or any part of the Premises is damaged by fire or other
          casualty, Tenant shall immediately notify Landlord in writing. During
          any period of time that all or more than 1,000 rentable square feet of
          the Premises is rendered untenantable as a result of a fire or other
          casualty, the Rent shall abate for the portion of the Premises that is
          untenantable and not used by Tenant. Landlord shall have the right to
          terminate this Lease if: (1) One Riverside Center shall be damaged so
          that, in Landlord's reasonable judgment, substantial alteration or
          reconstruction costing 50% or more of the replacement cost of One
          Riverside Center shall be required, or the Building shall be damaged
          so that, in Landlord's reasonable judgment, substantial alteration or
          reconstruction of the Building costing 50% or more of the replacement
          cost of the Building shall be required (whether or not the Premises
          has been damaged); (2) Landlord is not permitted by Law to rebuild the
          Building in substantially the same form as existed before the fire or
          casualty; or (3) a material uninsured loss to the Building occurs that
          arises out of a casualty of a type that is not covered under typical
          "all-risk" property insurance for the area in which the Building is
          located. In addition, if Two Riverside Center or Three Riverside
          Center shall be damaged so that, in Landlord's reasonable judgment,
          substantial alteration or reconstruction costing 75% or more of the
          replacement cost of Two Riverside Center or Three Riverside Center, as
          the case may be, shall be required, Landlord shall have the right to
          terminate this Lease with respect to the portion of the Premises
          located with such damaged portion of the Building. Notwithstanding the
          foregoing, except with respect to a casualty only affecting the
          Premises, Landlord's termination rights herein are conditioned upon
          Landlord's termination of all other tenancies within the Building
          where (i) the premises under such tenancies are similarly affected by
          the fire or other casualty, and (ii) Landlord has the right to
          terminate the lease with respect to such tenancy. Landlord may
          exercise its right to terminate this Lease by notifying Tenant in
          writing within 90 days after the date of the casualty. If this Lease
          shall not be terminated by either party pursuant to this Article XVII,
          Landlord shall commence and proceed with reasonable diligence to
          repair and restore the Building and the Leasehold Improvements
          (excluding any Alterations that were performed by Tenant in violation
          of this Lease). However, in no event shall Landlord be required to
          spend more than the insurance proceeds received by Landlord

                                       24
<PAGE>   28

          plus any deductible maintained by Landlord and any insurance proceeds
          that would have been received by Landlord but for a Mortgagee's
          (defined in Article XXVI) failure to release the same to Landlord;
          provided, that Landlord carries the insurance required by this Lease.
          Landlord shall not be liable for any loss or damage to Tenant's
          Property or to the business of Tenant resulting in any way from the
          fire or other casualty or from the repair and restoration of the
          damage. Landlord and Tenant hereby waive the provisions of any Law
          relating to the matters addressed in this Article, and agree that
          their respective rights for damage to or destruction of the Premises
          shall be those specifically provided in this Lease.

     B.   If all or any portion of the Premises shall be made untenantable by
          fire or other casualty, Landlord shall, within 90 days of the date of
          the fire or other casualty, cause a general contractor selected by
          Landlord and reasonably acceptable to Tenant to provide Landlord and
          Tenant with a written estimate of the amount of time required to
          substantially complete the repair and restoration of the Premises and
          make the Premises tenantable again, using standard working methods
          ("Completion Estimate"). If (1) the Completion Estimate indicates that
          the Premises cannot be made tenantable within 360 days from the date
          of the fire or other casualty, or (2) more than 50% of the Premises
          have been made untenantable by the fire or other casualty and less
          than one year will be remaining in the Term following the expected
          date of completion of restoration of the Premises as indicated in the
          Completion Estimate, then regardless of anything in Section XVII.A
          above to the contrary, either party shall have the right to terminate
          this Lease by giving written notice to the other of such election
          within 10 days after receipt of the Completion Estimate. Tenant,
          however, shall not have the right to terminate this Lease if the fire
          or casualty was caused by the negligence or intentional misconduct of
          Tenant, Tenant Related Parties or any of Tenant's transferees,
          contractors or licensees. If substantially all of the Premises was
          rendered untenantable by the fire or other casualty and Landlord does
          not substantially complete the repair and restoration of the Premises
          within two (2) months after the expiration of the estimated period of
          time set forth in the Completion Estimate, which period shall be
          extended to the extent of any Reconstruction Delays, then Tenant may
          terminate this Lease by written notice to Landlord within fifteen (15)
          days after the expiration of such period, as the same may be extended.
          For purposes of this Lease, the term "Reconstruction Delays" shall
          mean: (i) any delays caused by Tenant; and (ii) any delays caused by
          events of Force Majeure. Notwithstanding the provisions of this
          Subsection XVII.B. to the contrary, if the fire or casualty only
          affected the portion of the Premises located in Two Riverside Center
          or Three Riverside Center, and did not affect any portion of the
          Premises located in One Riverside Center, the termination rights set
          forth in this Subsection XVII.B shall be limited to the portion of the
          Premises located within such damaged portion of the Building.

XVIII. CONDEMNATION.

     Either party may terminate this Lease if the whole or any material part of
the Premises shall be taken or condemned for any public or quasi-public use
under Law or by eminent domain (a "Taking"). Landlord shall also have the right
to terminate this Lease if there is a Taking of any portion of the Building or
Property which would leave the remainder of the Building unsuitable for use as
an office building in a manner comparable to the Building's use prior to the
Taking. In order to exercise its right to terminate the Lease, Landlord or
Tenant, as the case may be, must provide written notice of termination to the
other within 45 days after the terminating party first receives notice of the
Taking. Any such termination shall be effective as of the date the physical
taking of the Premises or the portion of the Building or Property occurs. If
this Lease is not terminated, the Rentable Square Footage of the Building, the
Rentable Square Footage of the Premises and Tenant's Pro Rata Share shall, if
applicable, be appropriately adjusted. In addition, Rent for any portion of the
Premises taken or condemned shall be abated during the unexpired Term of this
Lease effective when the physical taking of the portion of the Premises occurs.
All compensation awarded for a Taking, or sale proceeds, shall be the property
of Landlord, any right to receive compensation or proceeds being expressly
waived by Tenant. However, Tenant may file a separate claim at its sole cost and
expense for Tenant's Property, the unamortized value of any Excess Costs
(defined in the Work Letter attached hereto as EXHIBIT D) and Tenant's
reasonable relocation expenses, provided the filing of the claim does not
diminish the award which would otherwise be receivable by Landlord.

XIX. EVENTS OF DEFAULT.

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     Tenant shall be considered to be in default of this Lease upon the
occurrence of any of the following events of default:

     A.   Tenant's failure to pay when due all or any portion of the Rent, if
          the failure continues for 5 days after written notice to Tenant
          ("Monetary Default").

     B.   Tenant's failure (other than a Monetary Default) to comply with any
          term, provision or covenant of this Lease, if the failure is not cured
          within 30 days after written notice to Tenant. However, if Tenant's
          failure to comply cannot reasonably be cured within 30 days, Tenant
          shall be allowed additional time (not to exceed 120 days) as is
          reasonably necessary to cure the failure so long as: (1) Tenant
          commences to cure the failure within 30 days, and (2) Tenant
          diligently pursues a course of action that will cure the failure and
          bring Tenant back into compliance with the Lease. However, if Tenant's
          failure to comply creates a hazardous condition, the failure must be
          cured immediately upon notice to Tenant. In addition, if Landlord
          provides Tenant with notice of Tenant's failure to comply with any
          particular term, provision or covenant of the Lease on 3 occasions
          during any 12 month period, Tenant's subsequent violation of such
          term, provision or covenant shall, at Landlord's option, be an
          immediate event of default by Tenant which shall not require written
          notice or a cure period.

     C.   Tenant becomes insolvent, makes a transfer in fraud of creditors or
          makes an assignment for the benefit of creditors, or admits in writing
          its inability to pay its debts when due.

     D.   The leasehold estate is taken by process or operation of Law and is
          not released within 30 days of such taking.

XX.  REMEDIES.

     A.   While any default is continuing, Landlord shall have the right without
          notice or demand (except as provided in Article XIX) to exercise any
          of its rights and remedies at Law or in equity, including any one or
          more of the remedies set forth below. Tenant shall not have the right
          to cure a default after the date on which Landlord has notified Tenant
          of its election to terminate this Lease, terminate Tenant's right of
          possession or exercise any other of Landlord's rights at Law or in
          equity.

          1.   Terminate this Lease, in which case Tenant shall immediately
               surrender the Premises to Landlord. If Tenant fails to surrender
               the Premises, Landlord may, in compliance with applicable Law and
               without prejudice to any other right or remedy, enter upon and
               take possession of the Premises and expel and remove Tenant,
               Tenant's Property and any party occupying all or any part of the
               Premises. Tenant shall pay Landlord on demand the amount of all
               past due Rent and other direct losses and damages (but
               specifically excluding indirect or consequential damages) which
               Landlord may suffer as a result of Tenant's default, whether by
               Landlord's inability to relet the Premises on reasonably
               satisfactory terms or otherwise, including, without limitation,
               all Costs of Reletting (defined below) and any deficiency that
               may arise from reletting or the failure to relet the Premises.
               "Costs of Reletting" shall include all reasonable costs and
               expenses incurred by Landlord in reletting or attempting to relet
               the Premises, including, without limitation, reasonable legal
               fees, brokerage commissions, the cost of alterations and the
               value of other concessions or allowances granted to a new tenant.

          2.   Terminate Tenant's right to possession of the Premises and, in
               compliance with applicable Law, expel and remove Tenant, Tenant's
               Property and any parties occupying all or any part of the
               Premises. Landlord may (but, except as provided in Section XX.C.
               below, shall not be obligated to) relet all or any part of the
               Premises, without notice to Tenant, for a term that may be
               greater or less than the balance of the Term and on such
               conditions (which may include concessions, free rent and
               alterations of the Premises) and for such uses as Landlord in its
               absolute discretion shall determine. Landlord may collect and
               receive all rents and other income from the reletting. Tenant
               shall pay Landlord on demand all past due Rent, all Costs of
               Reletting and any deficiency arising from the reletting or
               failure to relet the Premises. Landlord shall not be responsible
               or liable for the failure to relet all or any part of the
               Premises or for the failure to collect any Rent. The re-entry or
               taking of possession of the Premises shall not be construed as an
               election by Landlord to terminate this Lease unless a written
               notice of termination is given to Tenant.

                                       26
<PAGE>   30

          3.   In lieu of calculating damages under Sections XX.A.1 or XX.A.2
               above, Landlord may elect to receive as damages the sum of (a)
               all Rent accrued through the date of termination of this Lease or
               Tenant's right to possession, and (b) an amount equal to the
               total Rent that Tenant would have been required to pay for the
               remainder of the Term discounted to present value at the Prime
               Rate (defined in Section XX.B. below) then in effect, minus the
               then present fair rental value of the Premises for the remainder
               of the Term, similarly discounted, after deducting all
               anticipated Costs of Reletting.

     B.   Unless expressly provided in this Lease, the repossession or
          re-entering of all or any part of the Premises shall not relieve
          Tenant of its liabilities and obligations under the Lease. No right or
          remedy of Landlord shall be exclusive of any other right or remedy.
          Each right and remedy shall be cumulative and in addition to any other
          right and remedy now or subsequently available to Landlord at Law or
          in equity. If Landlord declares Tenant to be in default, Landlord
          shall be entitled to receive interest on any unpaid item of Rent at a
          rate equal to the Prime Rate plus 4%. For purposes hereof, the "Prime
          Rate" shall be the per annum interest rate publicly announced as its
          prime or base rate by a federally insured bank selected by Landlord in
          the state in which the Building is located. Forbearance by Landlord to
          enforce one or more remedies shall not constitute a waiver of any
          uncured default.

     C.   Landlord agrees to use reasonable efforts to mitigate damages,
          provided that such reasonable efforts shall not require Landlord to
          relet the Premises in preference to any other space in the Building or
          to relet the Premises to any party that Landlord could reasonably
          reject as a transferee pursuant to Article XII hereof.

XXI. LIMITATION OF LIABILITY.

     A.   NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN THIS LEASE, THE
          LIABILITY OF LANDLORD (AND OF ANY SUCCESSOR LANDLORD) TO TENANT SHALL
          BE LIMITED TO THE INTEREST OF LANDLORD IN THE PROPERTY. TENANT SHALL
          LOOK SOLELY TO LANDLORD'S INTEREST IN THE PROPERTY FOR THE RECOVERY OF
          ANY JUDGMENT OR AWARD AGAINST LANDLORD. NEITHER LANDLORD NOR ANY
          LANDLORD RELATED PARTY SHALL BE PERSONALLY LIABLE FOR ANY JUDGMENT OR
          DEFICIENCY. BEFORE FILING SUIT FOR AN ALLEGED DEFAULT BY LANDLORD,
          TENANT SHALL GIVE LANDLORD AND THE MORTGAGEE(S) (DEFINED IN ARTICLE
          XXVI BELOW) WHOM TENANT HAS BEEN NOTIFIED HOLD MORTGAGES (DEFINED IN
          ARTICLE XXVI BELOW) ON THE PROPERTY, BUILDING OR PREMISES, NOTICE AND
          REASONABLE TIME (NOT TO EXCEED 30 DAYS AFTER THE EXPIRATION OF ANY
          LANDLORD CURE PERIODS) TO CURE THE ALLEGED DEFAULT. NOTHING HEREIN
          SHALL LIMIT TENANT'S RIGHT TO BRING AN ACTION IN EQUITY AGAINST
          LANDLORD. IN NO EVENT, HOWEVER, SHALL TENANT BE ENTITLED TO BRING ANY
          SUCH ACTION AGAINST ANY TRUSTEE, MEMBER, PRINCIPAL, BENEFICIARY,
          PARTNER, OFFICER, DIRECTOR OR EMPLOYEE OF LANDLORD, OR MORTGAGEE
          (UNLESS SUCH MORTGAGEE IS IN POSSESSION OF THE PREMISES, BUILDING OR
          PROPERTY, OR HAS BECOME THE LANDLORD).

     B.   WITHOUT LIMITING THE SCOPE OF SECTION XXI.A. ABOVE (I) AND EXCEPT AS
          SPECIFICALLY PROVIDED IN SECTION III.E (LATE COMPLETION PENALTIES) TO
          THE CONTRARY, IN NO EVENT SHALL LANDLORD OR ANY MORTGAGEES OR LANDLORD
          RELATED PARTIES EVER BE LIABLE FOR ANY CONSEQUENTIAL OR INCIDENTAL
          DAMAGES OR ANY LOST PROFITS OF TENANT, AND (II) EXCEPT AS SPECIFICALLY
          PROVIDED IN SECTION XXV (HOLDOVER) TO THE CONTRARY, IN NO EVENT SHALL
          TENANT OR TENANT RELATED PARTIES EVER BE LIABLE FOR ANY CONSEQUENTIAL
          OR INCIDENTAL DAMAGES OR LOST PROFITS OF LANDLORD. THE PARTIES AGREE
          THAT THE EXCLUSION OF LOST PROFITS FROM DAMAGES SHALL NOT BE CONSTRUED
          AS TO LIMIT LANDLORD'S RIGHT TO COLLECT PAST AND FUTURE RENT DAMAGES
          UNDER SECTION XX.

XXII. NO WAIVER.

     Either party's failure to declare a default immediately upon its
occurrence, or delay in taking action for a default shall not constitute a
waiver of the default, nor shall it constitute an

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<PAGE>   31

estoppel unless such default is subsequently cured. Either party's failure to
enforce its rights for a default shall not constitute a waiver of its rights
regarding any subsequent default. Receipt by Landlord of Tenant's keys to the
Premises shall not constitute an acceptance or surrender of the Premises.

XXIII. QUIET ENJOYMENT.

     Tenant shall, and may peacefully have, hold and enjoy the Premises, subject
to the terms of this Lease, provided Tenant pays the Rent and fully performs all
of its covenants and agreements. This covenant and all other covenants of
Landlord shall be binding upon Landlord and its successors only during its or
their respective periods of ownership of the Building, and shall not be a
personal covenant of Landlord or the Landlord Related Parties.

XXIV. RELOCATION.

     Intentionally Omitted.

XXV. HOLDING OVER.

     Except for any permitted occupancy by Tenant under Article VIII, if Tenant
fails to surrender the Premises at the expiration or earlier termination of this
Lease, occupancy of the Premises after the termination or expiration shall be
that of a tenancy at sufferance. Tenant's occupancy of the Premises during the
holdover shall be subject to all the terms and provisions of this Lease and
Tenant shall pay an amount (on a per month basis without reduction for partial
months during the holdover) equal to 150% of the greater of: (1) the sum of the
Base Rent and Additional Rent due for the period immediately preceding the
holdover; or (2) the fair market gross rental for the Premises as reasonably
determined by Landlord. No holdover by Tenant or payment by Tenant after the
expiration or early termination of this Lease shall be construed to extend the
Term or prevent Landlord from immediate recovery of possession of the Premises
by summary proceedings or otherwise. In addition to the payment of the amounts
provided above, if Landlord is unable to deliver possession of the Premises to a
new tenant, or to perform improvements for a new tenant, as a result of Tenant's
holdover and Tenant fails to vacate the Premises within 60 days after the later
of (i) the Termination Date, or (ii) the date Landlord notifies Tenant of
Landlord's inability to deliver possession, or perform improvements, Tenant
shall be liable to Landlord for all damages, including, without limitation,
consequential damages, that Landlord suffers from the holdover.

XXVI. SUBORDINATION TO MORTGAGES; ESTOPPEL CERTIFICATE.

     A.   Subject to the provisions of subsection B. below, Tenant accepts this
          Lease subordinate to any mortgage(s), deed(s) of trust, ground
          lease(s) or other lien(s) subsequently arising upon the Premises, the
          Building or the Property, and to renewals, modifications, refinancings
          and extensions thereof (collectively referred to as a "Mortgage"). The
          party having the benefit of a Mortgage shall be referred to as a
          "Mortgagee". This clause shall be self-operative, but upon request
          from a Mortgagee, Tenant shall execute a commercially reasonable
          subordination agreement in favor of the Mortgagee. In lieu of having
          the Mortgage be superior to this Lease, a Mortgagee shall have the
          right at any time to subordinate its Mortgage to this Lease. If
          requested by a successor-in-interest to all or a part of Landlord's
          interest in the Lease, Tenant shall, without charge, attorn to the
          successor-in-interest; provided that such successor-in-interest
          assumes Landlord's obligations under this Lease with respect to the
          period from and after the date attornment is required. Landlord and
          Tenant shall each, within 10 days after receipt of a written request
          from the other, execute and deliver an estoppel certificate to those
          parties as are reasonably requested by the other (including a
          Mortgagee or prospective purchaser). The estoppel certificate shall
          include a statement certifying that this Lease is unmodified (except
          as identified in the estoppel certificate) and in full force and
          effect, describing the dates to which Rent and other charges have been
          paid, representing that, to such party's actual knowledge, there is no
          default (or stating the nature of the alleged default) and indicating
          other matters with respect to the Lease that may reasonably be
          requested.

     B.   Landlord hereby represents that the Building is not currently
          encumbered by a Mortgage. Landlord will use reasonable efforts to
          obtain a non-disturbance, subordination and attornment agreement in
          favor of Tenant from any future Mortgagee on such Mortgagee's then
          current standard form of agreement. Notwithstanding the foregoing,
          Tenant shall have the right to attempt to negotiate commercially
          reasonable changes to such future Mortgagee's form of non-disturbance,
          subordination and attornment

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<PAGE>   32

          agreement. Upon agreement between Tenant and such future Mortgagee,
          Tenant will execute such non-disturbance, subordination and attornment
          agreement and return the same to the future Mortgagee for execution.
          In the event that Tenant and any future Mortgagee are unable to agree
          upon the terms and conditions of the non-disturbance, subordination
          and attornment agreement, Tenant, upon request of such future
          Mortgagee, agrees to enter into a non-disturbance, subordination and
          attornment agreement on the form attached hereto as EXHIBIT J.
          Landlord's failure to obtain a non-disturbance, subordination and
          attornment agreement for Tenant from any future Mortgagee shall have
          no effect on the rights, obligations and liabilities of Landlord and
          Tenant or be considered to be a default by Landlord hereunder,
          provided that if such future Mortgagee is unwilling to enter into a
          non-disturbance, subordination and attornment agreement with Tenant
          (either on a negotiated form or the form attached hereto as EXHIBIT
          J), this Lease shall not be subordinated to the Mortgage held by the
          future Mortgagee. If, however, Tenant is unwilling to negotiate with
          the Mortgagee in good faith or to enter into such non-disturbance,
          subordination and attornment agreement on the form attached hereto as
          EXHIBIT J, such refusal shall be considered to be a default hereunder
          by Tenant and Landlord shall have no further obligation to attempt to
          obtain a non-disturbance, subordination and attornment from such
          future Mortgagee.

XXVII. ATTORNEYS' FEES.

     If either party institutes a suit against the other for violation of or to
enforce any covenant or condition of this Lease, or if either party intervenes
in any suit in which the other is a party to enforce or protect its interest or
rights, the prevailing party shall be entitled to all of its costs and expenses,
including, without limitation, reasonable attorneys' fees.

XXVIII. NOTICE.

     If a demand, request, approval, consent, invoice or notice (collectively
referred to as a "notice") shall or may be given to either party by the other,
the notice shall be in writing and delivered by hand or sent by registered or
certified mail with return receipt requested, or sent by overnight or same day
courier service at the party's respective Notice Address(es) set forth in
Article I, except that if Tenant has vacated the Premises (or if the Notice
Address for Tenant is other than the Premises, and Tenant has vacated such
address) without providing Landlord a new Notice Address, Landlord may serve
notice in any manner described in this Article or in any other manner permitted
by Law. Each notice shall be deemed to have been received or given on the
earlier to occur of actual delivery or the date on which delivery is refused,
or, if Tenant has vacated the Premises or the other Notice Address of Tenant
without providing a new Notice Address, three (3) days after notice is deposited
in the U.S. mail or with a courier service in the manner described above. Either
party may, at any time, change its Notice Address by giving the other party
written notice of the new address in the manner described in this Article.

XXIX. EXCEPTED RIGHTS.

     This Lease does not grant any rights to light or air over or about the
Building. Subject to the specific rights granted to Tenant in this Lease,
including, without limitation, Tenant's rights with respect to the use of the
Building risers and roof, Landlord excepts and reserves exclusively to itself
the use of: (1) roofs, (2) telephone, electrical and janitorial closets, (3)
equipment rooms, Building risers or similar areas that are used by Landlord for
the provision of Building services, (4) rights to the land and improvements
below the floor of the Premises, (5) the improvements and air rights above the
Premises; provided that Landlord may not add any additional floors to One
Riverside Center or Two Riverside Center, (6) the improvements and air rights
outside the demising walls of the Premises, and (7) the areas within the
Premises used for the installation of utility lines and other installations
serving occupants of the Building. Landlord has the right to change the
Building's name or address, provided that Landlord shall use reasonable efforts
to provide Tenant with at least 180 days prior notice with respect to a change
in the Building's street address that will prohibit Tenant from receiving mail
at the current address and in the event Landlord fails to provide Tenant with at
least 180 days prior notice, Landlord shall reimburse Tenant for the cost of
replacing all business stationery and promotional materials on hand (not to
exceed a two month's supply) at the effective date of such change. Landlord also
has the right to make such other changes to the Property and Building as
Landlord deems appropriate, provided the changes do not materially affect
Tenant's ability to use the Premises for the Permitted Use or materially affect
Tenant's use of the Premises as a first class office building. Landlord shall
also have the right (but not the obligation) to temporarily close the Building
if Landlord reasonably determines that there is an imminent danger of
significant damage to the Building or of personal injury to Landlord's

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<PAGE>   33

employees or the occupants of the Building. The circumstances under which
Landlord may temporarily close the Building shall include, without limitation,
electrical interruptions, hurricanes and civil disturbances. A closure of the
Building under such circumstances shall not constitute a constructive eviction
nor entitle Tenant to an abatement or reduction of Rent, except as otherwise
provided herein in this Lease.

XXX. SURRENDER OF PREMISES.

     At the expiration or earlier termination of this Lease or Tenant's right of
possession, Tenant shall remove Tenant's Property (defined in Article XV) from
the Premises, and quit and surrender the Premises to Landlord, broom clean, and
in good order, condition and repair, ordinary wear and tear excepted and subject
to the provisions of Articles XVII and XVIII. Tenant shall also be required to
remove the Required Removables in accordance with Article VIII. If Tenant fails
to remove any of Tenant's Property within 2 days after the termination of this
Lease or of Tenant's right to possession, Landlord, at Tenant's sole cost and
expense, shall be entitled (but not obligated) to remove and store such Tenant's
Property. Landlord shall not be responsible for the value, preservation or
safekeeping of such Tenant's Property. Tenant shall pay Landlord, upon demand,
the expenses and storage charges incurred for such Tenant's Property. In
addition, if Tenant fails to remove any of Tenant's Property from the Premises
or storage, as the case may be, within 30 days after written notice, Landlord
may deem all or any part of such Tenant's Property to be abandoned, and title to
such Tenant's Property shall be deemed to be immediately vested in Landlord.

XXXI. MISCELLANEOUS.

     A.   This Lease and the rights and obligations of the parties shall be
          interpreted, construed and enforced in accordance with the Laws of the
          state in which the Building is located and Landlord and Tenant hereby
          irrevocably consent to the jurisdiction and proper venue of such
          state. If any term or provision of this Lease shall to any extent be
          invalid or unenforceable, the remainder of this Lease shall not be
          affected, and each provision of this Lease shall be valid and enforced
          to the fullest extent permitted by Law. The headings and titles to the
          Articles and Sections of this Lease are for convenience only and shall
          have no effect on the interpretation of any part of the Lease.

     B.   Tenant shall not record this Lease. Landlord, however, agrees to
          execute and to deliver to Tenant for recordation or registration, at
          Tenant's cost and expense, a memorandum or notice of this Lease in the
          form attached hereto as EXHIBIT F. If this Lease is terminated before
          the Term expires, upon Landlord's request the parties shall execute,
          deliver and record an instrument acknowledging the above and the date
          of the termination of this Lease, and Tenant appoints Landlord its
          attorney-in-fact in its name and behalf to execute the instrument if
          Tenant shall fail to execute and deliver the instrument after
          Landlord's request therefor within 10 days.

     C.   Landlord and Tenant hereby waive any right to trial by jury in any
          proceeding based upon a breach of this Lease.

     D.   Whenever a period of time is prescribed for the taking of an action by
          Landlord or Tenant, the period of time for the performance of such
          action shall be extended by the number of days that the performance is
          actually delayed due to strikes, acts of God, shortages of labor or
          materials, war, civil disturbances and other causes beyond the
          reasonable control of the performing party (but in no event shall the
          term include economic or financing difficulties) ("Force Majeure").
          However, events of Force Majeure shall not extend any period of time
          for the payment of Rent or other sums payable by either party or any
          period of time for the written exercise of an option or right by
          either party. Notwithstanding anything herein to the contrary, except
          with respect to war, civil disturbance, fires, earthquakes, tornadoes,
          hurricanes and events that are commonly considered to be "acts of
          God", the number of days of Force Majeure delay with respect to each
          individual event of Force Majeure shall be limited to 60 days. For
          example, with respect to Landlord's performance of the Landlord Work,
          Landlord will not be able to claim more than 60 days of Force Majeure
          delay in connection with a strike by any individual construction trade
          or more than 60 days of Force Majeure delay in connection with the
          shortage of any particular type of materials. However, the number of
          days of Force Majeure delay in connection with any individual trade
          shall not be counted against the number of days of Force Majeure delay
          for an unrelated trade or an unrelated cause (such as a shortage of
          materials).

                                       30
<PAGE>   34

     E.   Landlord shall have the right to transfer and assign, in whole or in
          part, all of its rights and obligations under this Lease and in the
          Building and/or Property referred to herein, and upon such transfer
          and such successor's written assumption of Landlord's obligations
          under this Lease, Landlord shall be released from any further
          obligations hereunder, and Tenant agrees to look solely to the
          successor in interest of Landlord for the performance of such
          obligations.

     F.   Tenant represents that it has dealt directly with and only with the
          Broker as a broker in connection with this Lease. Tenant shall
          indemnify and hold Landlord and the Landlord Related Parties harmless
          from all claims of any other brokers claiming to have represented
          Tenant in connection with this Lease. Landlord agrees to indemnify and
          hold Tenant and the Tenant Related Parties harmless from all claims of
          any brokers claiming to have represented Landlord in connection with
          this Lease. Landlord shall be responsible for the payment of a
          brokerage commission to Broker in connection with this Lease in
          accordance with the terms of a separate agreement by and between
          Landlord and Broker.

     G.   (i). Tenant covenants, warrants and represents that: (1) each
          individual executing, attesting and/or delivering this Lease on behalf
          of Tenant is authorized to do so on behalf of Tenant; (2) this Lease
          is binding upon Tenant; and (3) Tenant is duly organized and legally
          existing in the state of its organization and is qualified to do
          business in the state in which the Premises are located. If there is
          more than one Tenant, or if Tenant is comprised of more than one party
          or entity, the obligations imposed upon Tenant shall be joint and
          several obligations of all the parties and entities. If Tenant is a
          partnership, then each present and future partner shall be personally
          bound by and upon all of the covenants, agreements, terms, provisions
          and conditions to be performed by Tenant. Landlord may request (and
          Tenant shall comply) that Tenant, at the time that Tenant admits any
          new partner to its partnership, require each new partner to execute an
          agreement in form and substance satisfactory to Landlord under which
          the new partner shall agree to be personally bound by and upon all of
          the covenants, agreements, terms, provisions and conditions to be
          performed by Tenant, without regard to when the new partner is
          admitted to the partnership (or when any obligations under any of
          covenants, agreements, terms, provisions and conditions accrue).
          Notices, payments and agreements given or made by, with or to any one
          person or entity shall be deemed to have been given or made by, with
          and to all of them.

          (ii). Landlord covenants, warrants and represents that: (1) each
          individual executing, attesting and/or delivering this Lease on behalf
          of Landlord is authorized to do so on behalf of Landlord; (2) this
          Lease is binding upon Landlord; and (3) Landlord is duly organized and
          legally existing in the state of its organization and is qualified to
          do business in the state in which the Premises are located.

     H.   Time is of the essence with respect to Tenant's exercise of any
          expansion, renewal or extension rights granted to Tenant. This Lease
          shall create only the relationship of landlord and tenant between the
          parties, and not a partnership, joint venture or any other
          relationship. This Lease and the covenants and conditions in this
          Lease shall inure only to the benefit of and be binding only upon
          Landlord and Tenant and their permitted successors and assigns.

     I.   The expiration of the Term, whether by lapse of time or otherwise,
          shall not relieve either party of any obligations which accrued prior
          to or which may continue to accrue after the expiration or early
          termination of this Lease. Without limiting the scope of the prior
          sentence, it is agreed that Tenant's obligations under Sections IV.A,
          IV.B., IV.D, VIII, XIV, XX, XXV and XXX and Landlord's obligations
          under Sections IV.B., IV.D., VI, XIV, and XX shall survive the
          expiration or early termination of this Lease.

     J.   Landlord has delivered a copy of this Lease to Tenant for Tenant's
          review only, and the delivery of it does not constitute an offer to
          Tenant or an option. This Lease shall not be effective against any
          party hereto until an original copy of this Lease has been signed by
          both parties.

     K.   All understandings and agreements previously made between the parties
          are superseded by this Lease, and neither party is relying upon any
          warranty, statement or representation not contained in this Lease.
          This Lease may be modified only by a written agreement signed by
          Landlord and Tenant.

                                       31
<PAGE>   35

     L.   Tenant, within 15 days after request, but not more than once in any 12
          month period, shall provide Landlord with a current financial
          statement and such other information as Landlord may reasonably
          request in order to create a "business profile" of Tenant and
          determine Tenant's ability to fulfill its obligations under this
          Lease. Landlord, however, shall not require Tenant to provide such
          information unless Landlord is requested to produce the information in
          connection with a proposed financing or sale of the Building. Upon
          written request by Tenant, Landlord shall enter into a commercially
          reasonable confidentiality agreement covering any confidential
          information that is disclosed by Tenant.

     M.   Landlord shall be in default under this Lease if Landlord fails to
          perform any of its obligations hereunder and said failure continues
          for a period of thirty (30) days after written notice from Tenant to
          Landlord describing the default in reasonable detail (provided that if
          such failure cannot reasonably be cured within thirty (30) days,
          Landlord shall be in default hereunder only if Landlord fails to
          commence to cure such default within thirty (30) days after notice
          from Tenant or having commenced the curative action within thirty (30)
          days, fails to diligently pursue same). Notwithstanding the foregoing
          cure period, Landlord shall be obligated to commence to cure an
          emergency situation that creates an imminent danger of bodily harm to
          any persons or an imminent danger of harm to property or material
          interference with Tenant's business operations as soon as reasonably
          possible following the date on which Landlord first became aware of
          such situation. Except to the extent the same have been waived by
          Tenant under the Lease, Tenant, following notice to Landlord and the
          expiration of the applicable cure period, shall be entitled to pursue
          any and all applicable remedies provided by Massachusetts law in
          connection with such default by Landlord hereunder. In lieu of
          exercising its rights and remedies under Massachusetts law, Tenant
          shall have the right to cure a default by Landlord under the limited
          circumstances where all of the following conditions exist (the "Self
          Help Conditions"): 1) all or substantially all of the Premises have
          been rendered unusable by Tenant for the Permitted Use as a result of
          Landlord's default; 2) Landlord has failed to cure the Landlord
          default within applicable notice and cure periods and, in addition,
          Landlord is not actively attempting to cure the default; 3) prior to
          curing the default, Tenant provides Landlord with written notice of
          the fact that Tenant intends to cure the default on Landlord's behalf;
          4) if there is a Mortgage on the Building, Tenant has provided such
          Mortgagee with notice of Landlord's default and has allowed such
          Mortgagee an opportunity to cure such default in accordance with the
          terms of any subordination, non-disturbance and attornment agreement
          (or similar agreement) between Tenant and such Mortgagee; 5) the
          action required to cure the default does not require Tenant to have
          access to the premises of any other tenant or occupant of the
          Building; and 6) the action required to cure the default does not
          involve the performance of work with respect to any Building systems
          (e.g. mechanical, electrical, plumbing, fire/life safety, card access)
          that are then operational and serving any other tenants or occupants
          of the Building. If all of the Self Help Conditions exist and Tenant
          elects to cure the default of Landlord, any such curative work must be
          performed by contractors that have previously performed similar work
          for Landlord in the Building, provided that the identity of such
          contractors are made known to Tenant. In addition, if Landlord has a
          warranty or service and maintenance agreement for a particular item
          that requires service, repair or replacement as part of the curative
          work (and Tenant is aware of such warranty or contract), Tenant shall
          contract with the issuer of such warranty or contract for the
          performance of the curative work so as not to adversely affect such
          warranty or contract. In attempting to cure any default by Landlord,
          Tenant shall pursue the least expensive course of action that can
          reasonably be expected to cure the default in question and shall
          perform only so much work as is reasonable necessary to cure the
          default. Tenant, in accordance with the terms of Article XIV, shall
          indemnify Landlord for any and all liabilities, obligations, damages,
          penalties, claims, actions, costs, charges and expenses in connection
          with the performance of such work, including any claims by tenants or
          occupants of the Building that are adversely affected by the
          performance of the work. Upon completion of the curative work by
          Tenant and receipt of paid invoices, Landlord shall reimburse Tenant
          for all expenses reasonably incurred by Tenant in curing Landlord's
          default. If Landlord fails to repay Tenant for such costs within
          fifteen (15) days after Landlord's receipt of the paid invoices,
          Tenant shall be entitled to pursue its remedies under Massachusetts
          law for payment of such amount.

XXXII. ENTIRE AGREEMENT.

This Lease and the following exhibits and attachments constitute the entire
agreement between the parties and supersede all prior agreements and
understandings related to the Premises, including all lease proposals, letters
of intent and other documents: EXHIBIT A (Outline and Location of

                                       32
<PAGE>   36

First Floor Premises in One Riverside Center), EXHIBIT A1 (Outline and Location
of Second Floor Premises in One Riverside Center), EXHIBIT A2 (Outline and
Location of Third Floor Premises in One Riverside Center), EXHIBIT A3 (Outline
and Location of First Floor Premises in Two Riverside Center), EXHIBIT A4
(Outline and Location of Second Floor Premises in Two Riverside Center) EXHIBIT
B (Rules and Regulations), EXHIBIT C (Commencement Letter), EXHIBIT D (Work
Letter Agreement), EXHIBIT E (Additional Provisions) and EXHIBIT F (Notice of
Lease), EXHIBIT G (Legal Description of Property), EXHIBIT H (Building Plan),
EXHIBIT I (Sample Letter of Credit), EXHIBIT J (Form of Non-Disturbance
Agreement. EXHIBIT K (Location of Parking Structure Sign), EXHIBIT L (Location
of One Riverside Center Sign), EXHIBIT M (Base Building Scope), EXHIBIT N
(Sample Cleaning Specifications), EXHIBIT O (Entry Signage), EXHIBIT P (First
Expansion Space).

     Landlord and Tenant have executed this Lease as of the day and year first
above written.

WITNESS/ATTEST:                   LANDLORD:

                                  EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE
                                  LIMITED LIABILITY COMPANY

                                  By:  Beacon Property Management Corporation, a
                                       Delaware corporation, its managing member
/s/ Kathleen M. Steidinger
------------------------------         By:    /S/ Michael A. Steele
                                             -------------------------------
Name (print):
              ----------------         Name:  Michael A. Steele
Kathleen M. Steidinger                       -------------------------------
------------------------------
                                       Title: President
/s/ John C. Schneider                        -------------------------------
------------------------------
Name (print):
              ----------------
John C. Schneider
------------------------------

WITNESS/ATTEST:                   TENANT:

                                  ALLAIRE CORPORATION, A CORPORATION ORGANIZED
/s/ Eric J. Smith                 UNDER THE LAWS OF THE STATE OF DELAWARE
------------------------------    By:    David A. Gerth
                                        ------------------------------------
Name (print): Eric J. Smith
             -----------------
/s/ JoAnne Trayers                Name:  David A. Gerth
------------------------------          ------------------------------------

Name (print): JoAnne Trayers      Title: CFO & VP Finance & Operations
             -----------------          ------------------------------------

------------------

                                       33
<PAGE>   37

                                    EXHIBIT A

    OUTLINE AND LOCATION OF THE FIRST FLOOR PREMISES IN ONE RIVERSIDE CENTER
    ------------------------------------------------------------------------

     This Exhibit is attached to and made a part of the Lease dated as of 23rd,
November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant") for space in the Building
located at 275 Grove Street, Newton, MA.

                                       1
<PAGE>   38

                                   EXHIBIT A-1

    OUTLINE AND LOCATION OF THE SECOND FLOOR PREMISES IN ONE RIVERSIDE CENTER
    -------------------------------------------------------------------------

     This Exhibit is attached to and made a part of the Lease dated as of 23rd,
November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant") for space in the Building
located at 275 Grove Street, Newton, MA.

                                       2
<PAGE>   39

                                   EXHIBIT A-2

    OUTLINE AND LOCATION OF THE THIRD FLOOR PREMISES IN ONE RIVERSIDE CENTER
    ------------------------------------------------------------------------

     This Exhibit is attached to and made a part of the Lease dated as 23rd,
November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant") for space in the Building
located at 275 Grove Street, Newton, MA.

                                       3
<PAGE>   40

                                   EXHIBIT A-3

    OUTLINE AND LOCATION OF THE FIRST FLOOR PREMISES IN TWO RIVERSIDE CENTER
    ------------------------------------------------------------------------

     This Exhibit is attached to and made a part of the Lease dated as of 23rd,
November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant") for space in the Building
located at 275 Grove Street, Newton, MA.

                                       4
<PAGE>   41

                                   EXHIBIT A-4

    OUTLINE AND LOCATION OF THE SECOND FLOOR PREMISES IN TWO RIVERSIDE CENTER
    -------------------------------------------------------------------------

     This Exhibit is attached to and made a part of the Lease dated as of 23rd,
November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant") for space in the Building
located at 275 Grove Street, Newton, MA.

                                       5
<PAGE>   42

                                    EXHIBIT B

                         BUILDING RULES AND REGULATIONS
                         ------------------------------

     The following rules and regulations shall apply, where applicable, to the
Premises, the Building, the parking garage (if any), the Property and the
appurtenances. Capitalized terms have the same meaning as defined in the Lease.

1.   Sidewalks, doorways, vestibules, halls, stairways and other similar areas
     not within the premises of any tenant of the Building shall not be
     obstructed by Tenant or used by Tenant for any purpose other than ingress
     and egress to and from the Premises. No rubbish, litter, trash, or material
     shall be placed, emptied, or thrown in those areas. At no time shall Tenant
     permit Tenant's employees to loiter in Common Areas or elsewhere about the
     Building or Property.

2.   Plumbing fixtures and appliances shall be used only for the purposes for
     which designed, and no sweepings, rubbish, rags or other unsuitable
     material shall be thrown or placed in the fixtures or appliances. Damage
     resulting to fixtures or appliances by the improper use by Tenant, its
     agents, employees or invitees, shall be paid for by Tenant, and Landlord
     shall not be responsible for the damage.

3.   No signs, advertisements or notices shall be painted or affixed to windows,
     doors or other parts of the Building, except those of such color, size,
     style and in such places as are first approved in writing by Landlord.
     Except in connection with the hanging of lightweight pictures and wall
     decorations, no nails, hooks or screws shall be inserted into any part of
     the Premises or Building except by the Building maintenance personnel or
     otherwise in accordance with the terms of Section IX.C.

4.   Landlord shall provide and maintain in the first floor (main lobby) of the
     Building an alphabetical directory board or other directory device listing
     tenants, and no other directory shall be permitted unless previously
     consented to by Landlord in writing.

5.   Tenant shall not place any lock(s) on any door in the Premises or Building
     without Landlord's prior written consent (which consent shall not be
     unreasonably withheld or delayed) and Landlord shall have the right to
     retain at all times and to use keys to all locks within and into the
     Premises. A reasonable number of keys to the locks on the entry doors in
     the Premises shall be furnished by Landlord to Tenant at Tenant's cost, and
     Tenant shall not make any duplicate keys. All keys shall be returned to
     Landlord at the expiration or early termination of this Lease.

6.   All contractors, contractor's representatives and installation technicians
     performing work in the Building shall be subject to Landlord's prior
     approval (which approval shall not be unreasonably withheld or delayed) and
     shall be required to comply with Landlord's standard rules, regulations,
     policies and procedures, which may be revised from time to time. Landlord
     has no obligation to allow any particular telecommunication service
     provider to have access to the Building or to the Premises, although
     Landlord agrees that Tenant may receive telecommunications service from MCI
     (or successor entity), and MCI (or successor entity) shall have access to
     the Building and the Premises for such purposes. Notwithstanding the
     foregoing, if Tenant wishes to receive telecommunications services from a
     different provider(s), Tenant shall have the right to advise Landlord of
     the provider or providers from whom Tenant would like to receive service at
     the Premises. Following receipt of such advice, Landlord shall use good
     faith efforts to enter into an agreement with such provider(s) on
     commercially reasonable terms and conditions for the Boston Suburban area,
     and upon Landlord's entering into such agreement, such provider(s) shall be
     permitted access to the Building and/or the Premises in order to provide
     telecommunications services to Tenant.

7.   Movement in or out of the Building of furniture or office equipment, or
     dispatch or receipt by Tenant of merchandise or materials requiring the use
     of elevators, stairways, lobby areas or loading dock areas, shall be
     restricted to hours designated by Landlord, the City of Newton or any other
     governmental authority having jurisdiction over the Building and Property.
     Tenant shall obtain Landlord's prior approval (which approval shall not be
     unreasonably withheld or delayed) by providing a detailed listing of the
     activity. If approved by Landlord, the activity shall be under the
     supervision of Landlord and performed in the manner required by Landlord.
     Tenant shall assume all risk for damage to articles moved and injury to any
     persons resulting from the activity. If equipment,

                                       1
<PAGE>   43

     property, or personnel of Landlord or of any other party is damaged or
     injured as a result of or in connection with the activity, Tenant shall be
     solely liable for any resulting damage or loss.

8.   Landlord shall have the right to approve the weight, size, or location of
     heavy equipment or articles in and about the Premises. Damage to the
     Building by the installation, maintenance, operation, existence or removal
     of property of Tenant shall be repaired at Tenant's sole expense.

9.   Corridor doors, when not in use, shall be kept closed.

10.  Tenant shall not: (1) make or permit any improper, objectionable or
     unpleasant noises or odors in the Building, or otherwise interfere in any
     way with other tenants or persons having business with them; (2) solicit
     business or distribute, or cause to be distributed, in any portion of the
     Building, handbills, promotional materials or other advertising; or (3)
     conduct or permit other activities in the Building that might, in
     Landlord's sole opinion, constitute a nuisance.

11.  No animals, except those assisting handicapped persons, shall be brought
     into the Building or kept in or about the Premises.

12.  No inflammable, explosive or dangerous fluids or substances shall be used
     or kept by Tenant in the Premises, Building or about the Property. Except
     for reasonable amounts of office and cleaning supplies which Tenant agrees
     to store on the Premises in compliance with applicable Law, Tenant shall
     not, without Landlord's prior written consent, use, store, install, spill,
     remove, release or dispose of, within or about the Premises or any other
     portion of the Property, any asbestos-containing materials or any solid,
     liquid or gaseous material now or subsequently considered toxic or
     hazardous under the provisions of 42 U.S.C. Section 9601 et seq., M.G.L. c.
     21C, M.G.L. c. 21E or any other applicable environmental Law which may now
     or later be in effect. Tenant shall comply with all Laws pertaining to and
     governing the use of these materials by Tenant, and shall remain solely
     liable for the costs of abatement and removal.

13.  Tenant shall not use or occupy the Premises in any manner or for any
     purpose which might injure the reputation or impair the present or future
     value of the Premises or the Building. Tenant shall not use, or permit any
     part of the Premises to be used, for lodging, sleeping or for any illegal
     purpose.

14.  Tenant shall not knowingly take any action which would violate Landlord's
     labor contracts or which would cause a work stoppage, picketing, labor
     disruption or dispute, or interfere with Landlord's or any other tenant's
     or occupant's business or with the rights and privileges of any person
     lawfully in the Building ("Labor Disruption"). Tenant shall take the
     actions reasonably necessary to resolve the Labor Disruption, and shall
     have pickets removed and, at the request of Landlord, immediately terminate
     any work in the Premises that gave rise to the Labor Disruption, until
     Landlord gives its written consent for the work to resume. Tenant shall
     have no claim for damages against Landlord or any of the Landlord Related
     Parties.

15.  Tenant shall not install, operate or maintain in the Premises or in any
     other area of the Building, electrical equipment that would overload the
     electrical system beyond its capacity for proper, efficient and safe
     operation as determined solely by Landlord. Tenant shall not furnish
     cooling or heating to the Premises, including, without limitation, the use
     of electronic or gas heating devices, without Landlord's prior written
     consent. Tenant shall not use more than its proportionate share of
     telephone lines and other telecommunication facilities available to service
     the Building, unless Tenant, at its sole cost and expense, causes
     additional lines and telecommunications to be installed, subject to the
     terms and conditions of this Lease.

16.  Tenant shall not operate or permit to be operated a coin or token operated
     vending machine or similar device (including, without limitation,
     telephones, lockers, toilets, scales, amusement devices and machines for
     sale of beverages, foods, candy, cigarettes and other goods), except for
     machines for the exclusive use of Tenant's employees.

17.  Bicycles and other vehicles are not permitted inside the Building or on the
     walkways outside the Building, except in areas designated by Landlord.

                                       2
<PAGE>   44

18.  Landlord may from time to time adopt systems and procedures for the
     security and safety of the Building, its occupants, entry, use and
     contents. Tenant, its agents, employees, contractors, guests and invitees
     shall comply with Landlord's systems and procedures.

19.  Landlord shall have the right to prohibit the use of the name of the
     Building or any other publicity by Tenant that in Landlord's sole opinion
     may impair the reputation of the Building or its desirability. Upon written
     notice from Landlord, Tenant shall refrain from and discontinue such
     publicity immediately.

20.  Tenant shall not canvass, solicit or peddle in or about the Building or the
     Property.

21.  Neither Tenant nor its agents, employees, contractors, guests or invitees
     shall smoke or permit smoking in the Common Areas, unless the Common Areas
     have been declared a designated smoking area by Landlord, nor shall the
     above parties allow smoke from the Premises to emanate into the Common
     Areas or any other part of the Building. Landlord shall have the right to
     designate the Building (including the Premises) as a non-smoking building.

22.  Landlord shall have the right to designate and approve standard window
     coverings for the Premises and to establish rules to assure that the
     Building presents a uniform exterior appearance. Tenant shall ensure, to
     the extent reasonably practicable, that window coverings are closed on
     windows in the Premises while they are exposed to the direct rays of the
     sun.

23.  Deliveries to and from the Premises shall be made only at the times, in the
     areas and through the entrances and exits designated by Landlord. Tenant
     shall not make deliveries to or from the Premises in a manner that might
     interfere with the use by any other tenant of its premises or of the Common
     Areas, any pedestrian use, or any use which is inconsistent with good
     business practice.

24.  The work of cleaning personnel shall not be hindered by Tenant after 5:30
     P.M., and cleaning work may be done at any time when the offices are
     vacant. Windows, doors and fixtures may be cleaned at any time. Tenant
     shall provide adequate waste and rubbish receptacles to prevent
     unreasonable hardship to the cleaning service. Tenant shall participate in
     Landlord's waste recycling program for the Building.

                                       3
<PAGE>   45

                                    EXHIBIT C

                               COMMENCEMENT LETTER
                               -------------------
                                    (EXAMPLE)

Date:

Allaire Corporation
Suite ____________________________________
One Riverside Center
275 Grove Street
Newton, MA

Re:  Commencement Letter with respect to that certain Lease dated as of , 1999,
     by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED LIABILITY
     COMPANY, as Landlord, and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
     UNDER THE LAWS OF THE STATE OF DELAWARE, as Tenant, for 270,446 rentable
     square feet space in the Building located at 275 Grove Street, Newton, MA.,
     a notice of which has been recorded with the Middlesex (South) Registry of
     Deeds in Book _____, Page _____.

Dear:    :

     In accordance with the terms and conditions of the above referenced Lease,
Tenant accepts possession of the Premises and agrees:

     1.   The Commencement Date of the Lease is             ;

     2.   The Termination Date of the Lease is                           (unless
sooner terminated or extended pursuant to the Lease).

     Please acknowledge your acceptance of possession and agreement to the terms
set forth above by signing all 3 counterparts of this Commencement Letter in the
space provided and returning 2 fully executed counterparts to my attention.

Sincerely,

Property Manager

Agreed and Accepted:

                 Tenant: ALLAIRE CORPORATION, A CORPORATION ORGANIZED UNDER THE
                    LAWS OF THE STATE OF DELAWARE

                 By:
                     -------------------------
                 Name:
                       -----------------------
                 Title:
                        ----------------------
                 Date:
                       -----------------------

                                       1
<PAGE>   46

                                STATE OF ILLINOIS

                       ss
---------------------,                             --------------------, ------
[County]

     Then personally appeared the above-named _____________, the _______________
of Beacon Property Management Corporation, a Delaware corporation, the managing
member of EOP-Riverside Project, L.L.C., a Delaware limited liability company,
known to me to be the person described in and who executed the foregoing
instrument and acknowledged the same to be his free act and deed and that of
said Beacon Property Management Corporation as the managing member of
EOP-Riverside Project, L.L.C., before me,

                                               ---------------------------------
                                               Notary Public
                                               My Commission Expires:

                          COMMONWEALTH OF MASSACHUSETTS

                       ss
---------------------,                             --------------------, ------
[County]

     Then personally appeared the above-named _____________, the _______________
of Allaire Corporation, a Delaware corporation, known to me to be the person
described in and who executed the foregoing instrument and acknowledged the same
to be his free act and deed and that of said Allaire Corporation, before me,

                                               ---------------------------------
                                               Notary Public
                                               My Commission Expires:

                                       2
<PAGE>   47

                                    EXHIBIT D

                                   WORK LETTER
                                   -----------

     This Exhibit is attached to and made a part of the Lease dated as of 23rd,
November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant") for space in the Building
located at 275 Grove Street, Newton, MA..

1.   This Work Letter shall set forth the obligations of Landlord and Tenant
     with respect to the preparation of the Premises for Tenant's occupancy.
     With the exception of Landlord's obligation to perform Base Building Work,
     all improvements described in this Work Letter to be constructed in and
     upon the Premises by Landlord are hereinafter referred to as the "Landlord
     Work." It is agreed that construction of the Landlord Work will be
     completed at Tenant's sole cost and expense, subject to the Allowance (as
     defined below). Landlord shall enter into separate direct contracts for the
     Landlord Work in the One Riverside Center Premises and the Two Riverside
     Center Premises with a general contractor(s) selected by Landlord and
     acceptable to Tenant, Tenant hereby agreeing that the selection of ADP
     Marshall is acceptable to Tenant. Landlord and Tenant agree that the
     identity of the general contractor for the One Riverside Center Premises
     and the Two Riverside Center Premises may be different. The contract with
     respect to the One Riverside Center Premises shall be entered into on the
     basis of the cost of work plus a three (3%) percent fee with a guaranteed
     maximum price, which price shall be inclusive of contractor's general
     conditions and overhead in the amount of Four Hundred Twenty-Seven Thousand
     Seven Hundred Seventy-Five Dollars ($427,775.00). In the event the Cost of
     the Landlord Work (defined below) with respect to the One Riverside Center
     Premises is less than the agreed upon guaranteed maximum price, the general
     contractor shall be entitled to receive 30% of the difference between the
     guaranteed maximum price and the actual cost of the Landlord Work; provided
     that in no event shall the general contractor's share of such savings
     exceed an amount equal to 20% of the amount of the general contractor's 3%
     fee with respect to the Landlord Work in the One Riverside Center Premises.
     The balance of such savings shall accrue to Tenant through a reduced Cost
     of Landlord Work (hereinafter defined). Landlord, Tenant and the general
     contractor shall work together in good faith to negotiate a mutually
     acceptable fee and general conditions arrangement with respect to the
     Landlord Work to be performed in the Two Riverside Center Premises, it
     being agreed that such arrangement has not been agreed to by the parties as
     of the date hereof. The financial terms and conditions of the contracts for
     the One Riverside Center Premises and Two Riverside Center Premises
     (including the guaranteed maximum price, and required retainage) and the
     terms of the general contractor's warranty (if Landlord does not obtain at
     least a one year warranty] shall be subject to Tenant's prior review and
     approval, such approval not to be unreasonably withheld, conditioned or
     delayed. The guaranteed maximum price of said contracts shall equal the
     Cost of Landlord Work (as defined in paragraph 5, below) with respect to
     the One Riverside Center Premises or Two Riverside Center Premises, as the
     case may be. Landlord shall have the right to require the general
     contractor to pay commercially reasonable late completion penalties in the
     event that ADP Marshall fails to complete the Landlord Work on or before
     the Target Commencement Date or Two Riverside Center Premises Target
     Commencement Date, as the case may be. The determination of whether a
     particular penalty provision is "commercially reasonable" shall take into
     consideration industry customs. Landlord agrees that each contract shall
     provide that all subcontracts shall be competitively bid to qualified
     subcontractors reasonably acceptable to Tenant. With respect to all
     portions of Landlord Work, Landlord or contractor shall provide Tenant with
     a list identifying at least three (3) responsible and qualified
     subcontractors to whom a portion of the Landlord Work is to be bid. Tenant
     shall have the right to identify additional qualified subcontractors for
     inclusion on such list. In order to be considered "qualified" hereunder, a
     subcontractor must: (a) be licensed to perform all aspects of the Landlord
     Work on which such subcontractor will submit a bid, (b) be capable of being
     bonded for all aspects of the Landlord Work on which such subcontractor
     will submit a bid, (c) maintain insurance of the types and amounts required
     by Landlord for the performance of the Landlord Work, (d) have a proven
     track record of on time completion of projects of comparable size and
     complexity in the Boston metropolitan and suburban area, as set forth on a
     resume to be submitted by such subcontractor to Landlord, (e) have
     sufficient personnel (including key supervisory personnel) dedicated to the
     performance of those

                                       1
<PAGE>   48

     portions of the Landlord Work on which such subcontractor will submit a
     bid, taking into consideration the possibility of overtime and the
     possibility that work may have to be performed following the targeted
     completion date, (f) not be a party to any contractual disputes or
     mechanics lien claims involving Landlord or any of its affiliated entities,
     and (g) submit a bid in strict compliance with the criteria set forth in
     Landlord's bid package. Unless otherwise agreed to by Tenant, Landlord
     agrees to award subcontracts to the lowest qualified bidder, provided that
     such bid accurately incorporates and reflects all of the criteria for bids
     issued by Landlord or Landlord's general contractor.

2.   Tenant shall be solely responsible for the timely preparation and
     submission to Landlord of all architectural, electrical and mechanical
     construction drawings, plans and specifications (called "Plans") necessary
     to construct the Landlord Work, which Plans shall be subject to reasonable
     approval by Landlord and Landlord's architect and engineers and shall
     comply with their requirements to avoid aesthetic or other conflicts with
     the design and function of the balance of the Building; provided, however,
     neither Landlord, nor its architect or engineer shall have any approval
     rights over aesthetic aspects of Landlord Work unless the same are visible
     from the exterior of the Building or the interior of the Building atrium.
     Tenant shall be responsible for all elements of the design of the Plans
     (including, without limitation, compliance with law, functionality of
     design, the structural integrity of the design, the configuration of the
     Premises and the placement of Tenant's furniture, appliances and
     equipment), and Landlord's approval of the Plans shall in no event relieve
     Tenant of the responsibility for such design; provided, however, if
     Landlord, Landlord's architect, engineer or contractor shall observe that
     any of the Plans are at variance with any applicable law, code, rule or
     regulation, Landlord, or its architect or contractor shall promptly notify
     Tenant and Tenant's architect in writing of such variance. Tenant shall
     have the right to submit Plans at one or more times and in one or more
     stages (for example, but not by way of limitation, proposed space plans may
     be submitted for approval prior to proposed engineering drawings, and
     proposed mechanical drawings may, in accordance with standard industry
     practice, be submitted in one or more portions). Within ten (10) Business
     Days after Landlord receives any such proposed Plans, or such portion
     thereof as has been submitted, Landlord shall either approve or disapprove
     the same (such approval not to be unreasonably withheld, conditioned or
     delayed). In the event of a disapproval by Landlord, Landlord shall
     describe in reasonable detail the grounds for such disapproval, and Tenant
     shall make those changes necessary in order to correct the problem(s) noted
     by Landlord in Landlord's notice of disapproval and shall return the
     drawings to Landlord, which Landlord shall approve or disapprove within
     five (5) Business Days after Landlord receives the revised Plans. This
     procedure shall be repeated until the Plans are finally approved by
     Landlord and written approval has been delivered to and received by Tenant.
     Notwithstanding the foregoing, Tenant shall submit to Landlord, for
     Landlord's review and approval (such approval not to be unreasonably
     withheld, conditioned or delayed): (i) Tenant's proposed "Design
     Development Plans" with respect to the Landlord Work in the One Riverside
     Center Premises by no later than November 12, 1999; and (ii) Tenant's
     proposed "Design Development Plans" with respect to the Landlord Work in
     the Two Riverside Center Premises by no later than February 14, 2000. For
     purposes hereof, the term "Design Development Plans" shall mean plans that
     are at least 80% complete so as to allow Landlord to order necessary Long
     Lead Items, as defined in paragraph 6 below.

3.   Landlord agrees to submit to Tenant, within ten (10) calendar days after
     receipt of Tenant's proposed Design Development Plans, an estimate of the
     anticipated cost of Landlord Work. Such estimate shall not be binding upon
     the parties.

4.   Tenant shall provide Landlord with final construction Plans (i.e. 100%
     complete) for the Landlord Work on or before: (i) December 10, 1999, with
     respect to the Landlord Work in the One Riverside Center Premises; and (ii)
     March 10, 2000, with respect to the Landlord Work in the Two Riverside
     Center Premises. Provided, that the final construction Plans are materially
     consistent with the Design Development Plans approved by Landlord, Landlord
     shall approve the final construction Plans on or before (a) December 15,
     1999 with respect to the Landlord Work in the One Riverside Center
     Premises, and (b) March 15, 2000 with respect to the Landlord Work in the
     Two Riverside Center Premises (each of such dates being referred to as the
     "Plans Due Date"). Notwithstanding the fact that the same defined terms of
     "Design Development Plans", "Plans", "Landlord Work", "Plans Due Date",
     "Cost of Landlord Work", "Long Lead Items" and "Change" are used with
     respect to both the One Riverside Center Premises and the Two Riverside
     Center Premises, Landlord and Tenant acknowledge that (x) the Landlord Work
     with respect to the One Riverside Center Premises and Two Riverside Center
     Premises shall be performed under separate contracts and,

                                       2
<PAGE>   49

     accordingly, the terms and conditions of this Work Letter will be applied
     separately with respect to each such contract, (y) any late completion
     penalties payable by Landlord under Article III of the Lease shall be
     calculated separately with respect to the One Riverside Center Premises and
     the Two Riverside Center Premises, and (z) any Tenant Delays for which
     Tenant is responsible shall be calculated separately with respect to the
     One Riverside Center Premises and the Two Riverside Center Premises. Time
     is of the essence in respect of preparation and submission of Plans by
     Tenant, and the review and approval of the same by Landlord. In the event
     the final construction Plans with respect to the One Riverside Center
     Premises are not fully completed and approved by the Plans Due Date due to
     (a) Tenant's failure to submit the final construction Plans on or before
     December 10, 1999, or (b) the failure of the final construction Plans to be
     materially consistent with the Design Development Plans approved by
     Landlord, Tenant shall be responsible for one (1) day of Tenant Delay (as
     defined in the Lease) for each day during the period beginning on the day
     following the Plans Due Date and ending on the date final construction
     Plans are approved. In the event the final construction Plans with respect
     to the Two Riverside Center Premises are not fully completed and approved
     by the Plans Due Date due to (a) Tenant's failure to submit the final
     construction Plans on or before March 10, 2000, or (b) the failure of the
     final construction Plans to be materially consistent with the Design
     Development Plans approved by Landlord, Tenant shall be responsible for one
     (1) day of Tenant Delay (as defined in the Lease) for each day during the
     period beginning on the day following the Plans Due Date and ending on the
     date final construction Plans are approved.

5.   Upon approval of the final construction Plans, the contractor shall solicit
     bids for Landlord Work from the list of subcontractors described in
     paragraph 1, above, as such list may have been reviewed and supplemented by
     Tenant. Landlord shall review all bids (together with back-up documentation
     and qualifications) with Tenant. Landlord shall within three (3) Business
     Days after receipt of such bids select the subcontractor for such portion
     of Landlord Work. Upon selection of all such subcontractors, Landlord and
     Tenant, together with the general contractor, shall within three (3)
     Business Days, mutually agree upon the cost of Landlord Work (which cost
     shall include the cost of labor and materials, the general contractor's
     fee, general conditions and permit fees). Upon agreement between Landlord,
     Tenant and the general contractor as to the total cost of the Landlord
     Work, (a) such total cost shall be deemed to be the "Cost of the Landlord
     Work"; (b) Landlord and the general contractor shall enter into the
     construction contract described in paragraph 1, above; and (c) Landlord
     shall cause the general contractor to commence construction of Landlord
     Work in accordance with the approved Plans.

6.   Based upon the Design Development Plans submitted by Tenant to Landlord,
     Landlord and Tenant will identify all portions of Landlord Work that are
     "critical" or "long lead" items (hereinafter, "Long Lead Items"); provided,
     however, Landlord and Tenant agree that, as of the date hereof, the
     following items are Long Lead Items: mechanical, electrical and plumbing
     fixtures and equipment; doors, door frames and related hardware; and
     carpeting. Landlord and Tenant acknowledge that, in order to complete the
     Landlord Work by the Target Completion Date or Two Riverside Center
     Premises Target Commencement Date, as the case may be, it will be necessary
     for Landlord to order certain Long Lead Items prior to completion of final
     construction Plans. As such, prior to the completion of final construction
     Plans, Landlord shall have the right to solicit bids and award subcontracts
     for Long Lead Items in accordance with the procedures described in
     paragraphs 1 and 6 above. Landlord shall submit to Tenant for its review
     all bids (together with back-up documentation and qualifications) received
     by Landlord or contractor with respect such Long Lead Items. Landlord shall
     within three Business Days after receipt of such bids select the
     subcontractor for such Long Lead Items. Upon selection of such
     subcontractors, (a) the cost of such Long Lead Items shall be fixed and
     binding upon Tenant, and shall be incorporated into the determination of
     the Cost of Landlord Work, and (b) Landlord may begin construction with
     respect to such Long Lead Items.

7.   If Tenant shall desire any change, addition or alteration in any of the
     Plans (collectively referred to as a "Change, Tenant shall describe the
     proposed Change to Landlord in writing, together with necessary revisions
     to the Plans. Within three (3) Business Days after receipt of Tenant's
     request for a Change, Landlord shall notify Tenant in writing of its
     approval or disapproval of the Change (such approval not to be unreasonably
     withheld or conditioned), together with (a) an analysis of the additional
     cost or saving involved and the period of time, if any, that the change
     will affect or delay the date on which the Landlord Work will be
     Substantially Complete ("Landlord's Analysis"), and (b)

                                       3
<PAGE>   50

     an authorization for Tenant's signature (the "Change Authorization"). In
     the event of a disapproval by Landlord, Landlord shall describe in
     reasonable detail the grounds for such disapproval. Upon receipt of such
     disapproval Tenant shall either make those changes necessary in order to
     correct the problem(s) noted by Landlord in Landlord's notice of
     disapproval or withdraw its request for a Change. If Tenant elects to
     revise the Plans, Landlord shall provide Tenant with written notice of
     approval or disapproval within three (3) Business Days after Landlord
     receives the revised Plans. This procedure shall be repeated until the
     Changes are finally approved by Landlord or withdrawn by Tenant. Upon
     Landlord's approval of the Change, Tenant may, within three (3) Business
     Days, send its signed Change Authorization instructing Landlord to proceed
     with such Change, in which event Landlord shall cause the Change to be
     made. In the absence of such signed Change Authorization, Landlord shall
     continue work on the Premises disregarding the requested Change. In the
     event Landlord's Analysis indicated that the authorized Change would result
     in an increase or savings in the Cost of Landlord Work, such increase or
     savings shall be added to or subtracted from the "Excess Costs" described
     in the following paragraph. In addition, if Landlord's Analysis indicated
     that the authorized Change would result in a delay or time savings with
     respect to the date on which Landlord Work would be Substantially Complete
     but for such Change, the net delay shall be deemed a Tenant Delay (as
     defined in the Lease).

8.   Landlord, provided Tenant is not in default under this Lease after the
     delivery of notice and the expiration of any applicable cure periods,
     agrees to provide Tenant with an allowance (the "Allowance") in an amount
     not to exceed Six Million Seven Hundred Sixty-One Thousand One Hundred
     Fifty and 00/100 Dollars ($6,761,150.00) (i.e., Twenty-Five and 00/100
     Dollars [$25.00] per rentable square foot of the Premises) to be applied
     toward the Cost of Landlord Work in the One Riverside Center Premises and
     Two Riverside Center Premises. In the event the Allowance is not sufficient
     to pay for the Cost of the Landlord Work in the One Riverside Center
     Premises and Two Riverside Center Premises and any other costs to which
     Tenant has previously elected to apply the Allowance in accordance with the
     procedures outlined below (such amounts exceeding the Allowance being
     herein referred to as the "Excess Costs"), Tenant shall pay to Landlord
     such Excess Costs as provided herein. As Landlord Work is completed,
     Landlord shall submit to Tenant's architect, but not more frequently than
     monthly, applications for payment received from the general contractor,
     along with such substantiation as the Tenant's architect may reasonably
     request (including invoices from subcontractors and materialsmen). Within
     five (5) Business Days after receipt of an application for payment,
     Landlord's architect and Tenant's architect shall verify that the labor,
     materials and/or equipment that is described in said application for
     payment has been properly performed and/or incorporated into the Premises,
     and shall promptly notify Tenant and Landlord of the same. Within five (5)
     Business Days after Tenant's receipt of such verification, Tenant shall
     make payment to Landlord in an amount equal to the product of the amount
     specified in the application for payment (or such other amount as Tenant's
     architect and Landlord's architect shall determine is properly due)
     multiplied by a fraction, the numerator of which is the Excess Costs, and
     the denominator of which is the total Cost of Landlord Work for the One
     Riverside Center Premises and Two Riverside Center Premises. In no event
     shall Tenant be required to make a payment for any labor, materials and/or
     equipment that has not been performed and/or incorporated into the
     Premises. The amounts payable by Tenant hereunder constitute Rent payable
     pursuant to the Lease, and the failure to timely pay the same shall
     constitute a default under the Lease.

9.   In the event the Allowance exceeds the total Cost of Landlord Work in the
     One Riverside Center Premises and Two Riverside Center Premises, Tenant
     shall be entitled to apply any remaining Allowance toward the cost of
     cabling and wiring in the Premises. Any unused portion of the Allowance
     that is not applied toward the Cost of the Landlord Work or the cost of
     wiring and cabling shall accrue to the sole benefit of Landlord, it being
     agreed that Tenant shall not be entitled to any credit, offset, abatement
     or payment with respect thereto. Landlord shall pay the Allowance directly
     to the contractors retained to perform the Landlord Work; provided,
     however, Landlord shall not make any payment without Landlord's architect
     and Tenant's architect having first verified that the labor, materials
     and/or equipment that is described in said application for payment has been
     properly performed and/or incorporated into the Premises, and that the
     requested amount is properly due. Notwithstanding the foregoing, if
     Landlord's architect and Tenant's architect can not agree as to whether a
     particular payment, or portion thereof, is properly due, Landlord shall
     have the right to make payment with respect only to the portion of the
     request for payment that is not in dispute. If Landlord withholds payment
     of any amount based on the improper recommendation of Tenant's

                                       4
<PAGE>   51

     architect, Tenant shall indemnify Landlord for any mechanics liens or other
     claims that are asserted as a result of Landlord's failure to pay that
     portion of the Cost of the Landlord Work that is withheld. In addition, any
     slow down or stoppage of the performance of Landlord Work as a result of
     the improper recommendation of Tenant's architect (without the concurrence
     of Landlord's architect) to withhold any such payment shall be considered
     to be a Tenant Delay. Any portion of the Allowance that Tenant elects to
     apply toward costs not directly relating to the Landlord Work (i.e. the
     cost of cabling and wiring) shall be paid to Tenant within thirty (30) days
     after Landlord's receipt of paid invoices from Tenant evidencing Tenant's
     payment of the amounts to which the Allowance will be applied.

10.  In addition to Landlord's obligation to provide Tenant with an Allowance,
     Landlord, provided Tenant is not in default under the Lease after the
     delivery of notice and the expiration of any applicable cure periods, shall
     provide Tenant with an allowance (the "Architectural and Engineering
     Allowance") in the amount of $540,892.00 (i.e., $2.00 per rentable square
     foot of the Premises) to be applied toward the cost of architectural and
     engineering services for the Premises contracted by Tenant. Landlord shall
     disburse the Architectural and Engineering Allowance, or applicable portion
     thereof, to Tenant within thirty (30) days after Landlord's receipt of
     invoices and lien waivers from Tenant with respect to Tenant's actual
     engineering and architectural fees as described above. Any unused portion
     of the Architectural and Engineering Allowance may be applied toward the
     Cost of the Landlord Work. Any unused portion that is not applied toward
     the Cost of Landlord Work shall accrue to the sole benefit of Landlord, it
     being agreed that Tenant shall not be entitled to any credit, offset,
     abatement or payment with respect thereto.

11.  In addition to the Landlord Work, Landlord shall be responsible for
     performing the Base Building Work in the Premises as described in the Base
     Building Scope attached to the Lease as EXHIBIT M. All Base Building Work
     shall be performed at Landlord's sole cost and expense. In no event shall
     the cost of the Base Building Work be applied against or deducted from the
     Allowance or Architectural and Engineering Allowance. Notwithstanding the
     foregoing, Landlord shall have the right to change the plans and
     specifications for the Base Building Work from time to time, provided that
     Landlord shall not materially reduce the overall quality of the Base
     Building Work; provided, further, that Tenant shall have the right to
     approve any such changes that materially affect Tenant's occupancy,
     operation or design of the Premises, which approval shall not be
     unreasonably withheld or delayed.

12.  Tenant's architect and/or construction representative and Landlord's
     architect and/or construction representative shall meet weekly to discuss
     the progress of the construction of Landlord Work and the expected dates on
     which the One Riverside Center Premises and the Two Riverside Center
     Premises, as the case may be, will be Substantially Complete. In addition,
     Tenant's architect and/or construction representative shall be permitted to
     attend regularly scheduled job meetings during the course of construction
     of Landlord Work in the One Riverside Center Premises and Two Riverside
     Center Premises and shall be provided with copies of the minutes of all job
     meetings relating to the Landlord Work in the One Riverside Center Premises
     and Two Riverside Center Premises, which minutes shall include information
     relating to the date on which each such portion of the Premises will be
     Substantially Complete.

13.  As used in this EXHIBIT D, the word "architect" shall include an interior
     designer or space planner.

14.  This Exhibit D shall not be deemed applicable to any additional space added
     to the original Premises at any time or from time to time, whether by any
     options under the Lease or otherwise, or to any portion of the original
     Premises or any additions to the Premises in the event of a renewal or
     extension of the original Term of this Lease, whether by any options under
     the Lease or otherwise.

15.  All Landlord's Work and Base Building Work shall be performed in a good and
     workmanlike manner using quality materials in compliance with all
     applicable Laws; provided that Tenant, not Landlord, shall be responsible
     for the cost of correcting of any violations of Law with respect to the
     Landlord Work that arise out of a failure by Tenant's architect to prepare
     the Plans in strict compliance with all Laws, including the ADA.

                                       5
<PAGE>   52

     Landlord and Tenant have executed this exhibit as of the day and year first
     above written.

WITNESS/ATTEST:                 LANDLORD:

                                EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
                                LIABILITY COMPANY

                                By:  Beacon Property Management Corporation, a
                                     Delaware corporation, its managing member
/s/ Kathleen M. Steidinger
-----------------------------        By:     /s/ Michael A. Steele
                                            -------------------------
Name (print):
              ---------------        Name:   Michael A. Steele
Kathleen M. Steidinger                      -------------------------
-----------------------------
                                     Title:  President
/s/ John C. Schneider                       -------------------------
-----------------------------
Name (print):
              ---------------
John C. Schneider
-----------------------------

WITNESS/ATTEST:                 TENANT:

                                ALLAIRE CORPORATION, A CORPORATION ORGANIZED
/s/ Eric J. Smith               UNDER THE LAWS OF THE STATE OF DELAWARE
-----------------------------   By:     David A. Gerth
                                       ------------------------------
Name (print): Eric J. Smith
              ---------------   Name:   David A. Gerth
/s/ JoAnne Trayers                     ------------------------------
-----------------------------
                                Title:  CFO & VP Finance & Operations
Name (print): JoAnne Trayers           ------------------------------
              ---------------

-----------------------------

                                       6
<PAGE>   53

                                    EXHIBIT E

                              ADDITIONAL PROVISIONS
                              ---------------------

     This Exhibit is attached to and made a part of the Lease dated as of 23rd,
November, 1999, by and between EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
LIABILITY COMPANY ("Landlord") and ALLAIRE CORPORATION, A CORPORATION ORGANIZED
UNDER THE LAWS OF THE STATE OF DELAWARE ("Tenant") for space in the Building
located at 275 Grove Street, Newton, MA.

I.   FIRST RENEWAL OPTION.
     ---------------------

     A.   Tenant shall have the right to extend the Term (the "First Renewal
          Option") for one additional period of 5 years commencing on the day
          following the Termination Date of the initial Term and ending on the
          5th anniversary of the Termination Date (the "First Renewal Term"),
          if:

          1.   Landlord receives notice of exercise of the First Renewal Option
               ("Initial First Renewal Notice") on or before to the last day of
               the 105th full calendar month following the Commencement Date;
               and

          2.   Tenant is not in default under the Lease beyond any applicable
               notice and cure periods at the time that Tenant delivers its
               Initial First Renewal Notice or at the time Tenant delivers its
               First Binding Notice (hereinafter defined); and

          3.   No more than thirty percent (30%) of the Premises is sublet
               (except in connection with a Permitted Transfer) at the time that
               Tenant delivers its Initial First Renewal Notice or at the time
               Tenant delivers its First Binding Notice; and

          4.   The Lease has not been assigned (except in connection with a
               Permitted Transfer) prior to the date that Tenant delivers its
               Initial First Renewal Notice or prior to the date Tenant delivers
               its First Binding Notice.

     B.   The initial Base Rent rate per rentable square foot for the Premises
          during the First Renewal Term shall equal the Prevailing Market
          (hereinafter defined) rate per rentable square foot for the Premises.

     C.   Tenant shall pay Additional Rent (i.e. Tenant's Pro Rata Share of
          Expense Excess and Tenant's Pro Rata Share of Tax Excess) for the
          Premises during the First Renewal Term in accordance with Article IV
          of the Lease.

     D.   Within 30 days after receipt of Tenant's Initial First Renewal Notice,
          Landlord shall advise Tenant of the applicable Base Rent rate for the
          Premises for the First Renewal Term (a "Prevailing Market Notice"),
          provided in no event shall Landlord be required to provide Tenant with
          a Prevailing Market Notice prior to the last day of the 105th full
          calendar month following the Commencement Date. Tenant, within 15 days
          after the date on which Tenant receives the Prevailing Market Notice,
          shall either (i) give Landlord final binding written notice ("First
          Binding Notice") of Tenant's exercise of its option, or (ii) if Tenant
          disagrees with Landlord's determination, provide Landlord with written
          notice of rejection (the "Rejection Notice"). If Tenant fails to
          provide Landlord with either a First Binding Notice or Rejection
          Notice within such 15 day period, Tenant's First Renewal Option shall
          be null and void

                                       1
<PAGE>   54

          and of no further force and effect. If Tenant provides Landlord with a
          First Binding Notice, Landlord and Tenant shall enter into the First
          Renewal Amendment upon the terms and conditions set forth herein. If
          Tenant provides Landlord with a Rejection Notice, Landlord and Tenant
          shall work together in good faith to agree upon the Prevailing Market
          Base Rent rate for the Premises during the First Renewal Term. Upon
          agreement Tenant shall provide Landlord with First Binding Notice and
          Landlord and Tenant shall enter into the First Renewal Amendment
          (hereinafter defined) in accordance with the terms and conditions
          hereof. Notwithstanding the foregoing, if Landlord and Tenant are
          unable to agree upon the Prevailing Market Base Rent rate for the
          Premises within 30 days after the date on which Tenant provides
          Landlord with a Rejection Notice, Tenant shall have the option to
          withdraw its Initial First Renewal Notice by giving Landlord written
          notice of such withdrawal within 10 days after the expiration of such
          30 day period. If Tenant elects to withdraw its Initial First Renewal
          Notice, Tenant's right to extend the term of the Lease shall be null
          and void and of no further force and effect. If Landlord and Tenant
          cannot agree upon Prevailing Market Base Rent within the 30 day period
          described above and, in addition, Tenant does not elect to withdraw
          its Initial First Renewal Notice, Landlord and Tenant, within 20 days
          after the expiration of the 30 day period, shall each simultaneously
          submit to the other, in a sealed envelope, its good faith estimate of
          the Prevailing Market Base Rent rate for the Premises during the First
          Renewal Term (collectively referred to as the "Estimates"). If the
          higher of such Estimates is not more than 105% of the lower of such
          Estimates, then Prevailing Market Base Rent rate shall be the average
          of the two Estimates. If the Prevailing Market Base Rent rate is not
          resolved by the exchange of Estimates, Landlord and Tenant, within 7
          days after the exchange of Estimates, shall each select a appraiser to
          determine which of the two Estimates most closely reflects the
          Prevailing Market Base Rent rate for the Premises during the First
          Renewal Term. Each appraiser so selected shall be certified as an MAI
          appraiser or as an ASA appraiser and shall have had at least 5 years
          experience within the previous 10 years as a real estate appraiser
          working in the Newton, Massachusetts area, with working knowledge of
          current rental rates and practices. For purposes of this Lease, an
          "MAI" appraiser means an individual who holds an MAI designation
          conferred by, and is an independent member of, the American Institute
          of Real Estate Appraisers (or its successor organization, or in the
          event there is no successor organization, the organization and
          designation most similar), and an "ASA" appraiser means an individual
          who holds the Senior Member designation conferred by, and is an
          independent member of, the American Society of Appraisers (or its
          successor organization, or, in the event there is no successor
          organization, the organization and designation most similar). Upon
          selection, Landlord's and Tenant's appraisers shall work together in
          good faith to agree upon which of the two Estimates most closely
          reflects the Prevailing Market Base Rent rate. The Estimate chosen by
          such appraisers shall be binding on both Landlord and Tenant as the
          Base Rent rate for the First Renewal Term. If either Landlord or
          Tenant fails to appoint an appraiser within the 7 day period referred
          to above, the appraiser appointed by the other party shall be the sole
          appraiser for the purposes hereof. If the two appraisers cannot agree
          upon which of the two Estimates most closely reflects the Prevailing
          Market Base Rent within the 20 days after their appointment, then,
          within 10 days after the expiration of such 20 day period, the 2
          appraisers shall select a third appraiser meeting the aforementioned
          criteria. Once the third appraiser has been selected as provided for
          above, then, as soon thereafter as practicable but in any case within
          14 days, the third appraiser shall make his determination of which of
          the two Estimates most closely reflects the Prevailing Market Base
          Rent rate and such Estimate shall be binding on both Landlord and
          Tenant as the Base Rent rate for the First Renewal Term. If the third
          appraiser believes that expert advice would materially assist him, he
          may retain one or more qualified persons, to provide such expert
          advice. The parties shall share equally in the costs of the third
          appraiser and of any experts retained by the third appraiser. Any fees
          of any counsel or experts engaged directly by Landlord or Tenant,
          however, shall be borne by the party retaining such counsel or expert.
          In the event that the Prevailing Market Base Rent rate has not been
          determined by the end of the initial Term, Tenant shall continue to
          pay Base Rent upon the terms and conditions in effect for the last
          month of the initial Term until such time as the Prevailing Market
          Base Rent rate has been determined. Upon such determination, the Base
          Rent for the First Renewal Term shall be retroactively adjusted to the
          commencement of the First Renewal Term. If such adjustment results in
          an underpayment of Base Rent by Tenant, Tenant shall pay Landlord the
          amount of such underpayment within 30 days after the determination
          thereof. If such adjustment results in an overpayment of Base Rent by
          Tenant, Landlord shall credit such overpayment against the next
          installment of Base Rent due under the Lease and, to the extent
          necessary, any subsequent installments until the entire amount of such
          overpayment has been credited against Base Rent.

     E.   If Tenant is entitled to and properly exercises its First Renewal
          Option, Landlord shall prepare an amendment (the "First Renewal
          Amendment") to reflect changes in the Base Rent, Term, Termination
          Date and other appropriate terms. The First Renewal Amendment shall
          be:

          1.   sent to Tenant within a reasonable time after receipt of the
               First Binding Notice or the determination of Prevailing Market
               Base Rent pursuant to the appraisal procedure described above;
               and

          2.   revised by Landlord to address any requested changes by Tenant
               that

                                       2
<PAGE>   55

               are reasonably necessary to accurately reflect the terms and
               conditions hereof; and

          3.   executed by Tenant and returned to Landlord within fifteen (15)
               days after such First Renewal Amendment (together with such
               changes described in the immediately preceding paragraph) is
               delivered to Tenant by Landlord who shall promptly countersign
               the same and return a fully executed counterpart to Tenant.

          An otherwise valid exercise of the First Renewal Option shall be fully
          effective whether or not the First Renewal Amendment is executed.

     F.   For purposes of this Section I and Section II (Second Renewal Option)
          below only, "Prevailing Market" shall mean the arms length fair market
          annual base rental rate per rentable square foot under renewal leases
          and renewal amendments entered into on or about the date on which the
          Prevailing Market is being determined hereunder for space comparable
          to the Premises in the Building and office buildings comparable to the
          Building in the Route 128 western submarket of Newton, Wellesley and
          Waltham. The determination of Prevailing Market Base Rent rate shall
          take into account any material economic differences between this Lease
          and the renewal leases and renewal amendments that are being used for
          comparison purposes, including: (i) the value of any amenities (e.g.
          parking, cafeteria) offered by Landlord or any comparison landlord
          (i.e. offered by one, but not the other) without an additional charge
          over base rent, (ii) the value of any economic concessions (e.g rental
          abatements, refurbishment allowances) offered by a comparison landlord
          and not offered by Landlord, it being understood that Tenant shall not
          be entitled to receive any economic concessions during the First
          Renewal Term; (iii) the difference (on a rentable square foot basis)
          between any broker commissions payable by Landlord in connection with
          the First Renewal Term and any brokerage commissions payable by
          another landlord in connection with a comparison renewal lease or
          renewal amendment; and (iv) the differences in the way Landlord and
          the landlord under any comparison renewal lease or renewal amendment
          is reimbursed for operating expenses and taxes. The determination of
          Prevailing Market shall also take into consideration any reasonably
          anticipated changes in the Prevailing Market rate from the time such
          Prevailing Market rate is being determined and the time such
          Prevailing Market Base Rent rate will become effective under this
          Lease. Notwithstanding anything herein to the contrary, if any
          comparison renewal lease or renewal amendment provides for an
          improvement allowance or refurbishment allowance, the effect of such
          allowance on the Prevailing Market rate shall be determined by
          comparing the rental value of the Premises in its "as-is" condition
          against the actual or anticipated rental value of the comparison
          premises after such premises have been improved by the expenditure of
          the improvement allowance or refurbishment allowance. For example, if,
          after the expenditure of the improvement allowance or refurbishment
          allowance, the comparison premises are improved to a condition that is
          not materially better or materially worse than the "as-is" condition
          of the Premises (i.e. the buildout of the two spaces is comparable),
          the grant of such improvement allowance or refurbishment allowance
          shall not be taken into consideration in the determination of the ---
          Prevailing Market rate. However, if the expenditure of the improvement
          allowance or refurbishment allowance would bring the comparison
          premises into a condition that is materially better or materially
          worse than the "as-is" condition of the Premises, then the difference
          between the condition of the two premises and the affect on the rental
          value shall be taken into consideration in the determination of the
          Prevailing Market rate. However, the actual dollar per square foot
          improvement allowance or refurbishment allowance shall not be used as
          the basis for comparison.

II.  SECOND RENEWAL OPTION.
     ----------------------

     A.   Tenant shall have the right to extend the First Renewal Term (the
          "Second Renewal Option") for one additional period of 5 years
          commencing on the day following the Termination Date of the First
          Renewal Term and ending on the 5th anniversary of the Termination Date
          of the First Renewal Term (the "Second Renewal Term"), if:

          1.   Landlord receives notice of exercise of the Second Renewal Option
               ("Initial Second Renewal Notice") on or before to the last day of
               the 45th full calendar month of the First Renewal Term; and

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<PAGE>   56

          2.   Tenant is not in default under the Lease beyond any applicable
               notice and cure periods at the time that Tenant delivers its
               Initial Second Renewal Notice or at the time Tenant delivers its
               Second Binding Notice (hereinafter defined); and

          3.   No more than thirty percent (30%) of the Premises is sublet
               (except in connection with a Permitted Transfer) at the time that
               Tenant delivers its Initial Second Renewal Notice or at the time
               Tenant delivers its Second Binding Notice; and

          4.   The Lease has not been assigned (except in connection with a
               Permitted Transfer) prior to the date that Tenant delivers its
               Initial Second Renewal Notice or prior to the date Tenant
               delivers its Second Binding Notice; and

          5.   Tenant has previously extended the Term of the Lease for the
               First Renewal Term.

     B.   The initial Base Rent rate per rentable square foot for the Premises
          during the Second Renewal Term shall equal the Prevailing Market rate
          per rentable square foot for the Premises as defined in Section I.E
          above, provided that any references to the First Renewal Term in
          Section I.E. shall be deemed to refer to the Second Renewal Term.

     C.   Tenant shall pay Additional Rent (i.e. Tenant's Pro Rata Share of
          Expense Excess and Tenant's Pro Rata Share of Tax Excess) for the
          Premises during the Second Renewal Term in accordance with Article IV
          of the Lease.

     D.   Within 30 days after receipt of Tenant's Initial Second Renewal
          Notice, Landlord shall advise Tenant of the applicable Base Rent rate
          for the Premises for the Second Renewal Term (a "Prevailing Market
          Notice"), provided in no event shall Landlord be required to provide
          Tenant with a Prevailing Market Notice prior to the last day of the
          45th full calendar month of the First Renewal Term. Tenant, within 15
          days after the date on which Tenant receives the Prevailing Market
          Notice, shall either (i) give Landlord final binding written notice
          ("Second Binding Notice") of Tenant's exercise of its option, or (ii)
          if Tenant disagrees with Landlord's determination, provide Landlord
          with written notice of rejection (the "Rejection Notice"). If Tenant
          fails to provide Landlord with either a Second Binding Notice or
          Rejection Notice within such 15 day period, Tenant's Second Renewal
          Option shall be null and void and of no further force and effect. If
          Tenant provides Landlord with a Second Binding Notice, Landlord and
          Tenant shall enter into the Second Renewal Amendment upon the terms
          and conditions set forth herein. If Tenant provides Landlord with a
          Rejection Notice, Landlord and Tenant shall work together in good
          faith to agree upon the Prevailing Market Base Rent rate for the
          Premises during the Second Renewal Term. Upon agreement Tenant shall
          provide Landlord with Second Binding Notice and Landlord and Tenant
          shall enter into the Second Renewal Amendment (hereinafter defined) in
          accordance with the terms and conditions hereof. Notwithstanding the
          foregoing, if Landlord and Tenant are unable to agree upon the
          Prevailing Market Base Rent rate for the Premises within 30 days after
          the date on which Tenant provides Landlord with a Rejection Notice,
          Tenant shall have the option to withdraw its Initial Second Renewal
          Notice by giving Landlord written notice of such withdrawal within 10
          days after the expiration of such 30 day period. If Tenant elects to
          withdraw its Initial Second Renewal Notice, Tenant's right to extend
          the term of the Lease shall be null and void and of no further force
          and effect. If Landlord and Tenant cannot agree upon Prevailing Market
          Base Rent within the 30 day period described above and, in addition,
          Tenant does not elect to withdraw its Initial Second Renewal Notice,
          the Prevailing Market Base Rent rate for the Premises during the
          Second Renewal Term shall be determined by binding arbitration in
          accordance with the procedures described in Section I above.

     E.   If Tenant is entitled to and properly exercises its Second Renewal
          Option, Landlord shall prepare an amendment (the "Second Renewal
          Amendment") to reflect changes in the Base Rent, Term, Termination
          Date and other appropriate terms. The Second Renewal Amendment shall
          be:

          1.   sent to Tenant within a reasonable time after receipt of the
               Second Binding Notice or the determination of Prevailing Market
               Base Rent pursuant to the appraisal procedure described above;
               and

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<PAGE>   57

          2.   revised by Landlord to address any requested changes by Tenant
               that are reasonably necessary to accurately reflect the terms and
               conditions hereof; and

          3.   executed by Tenant and returned to Landlord within fifteen (15)
               days after such Second Renewal Amendment (together with such
               changes described in the immediately preceding paragraph) is
               delivered to Tenant by Landlord who shall promptly countersign
               the same and return a fully executed counterpart to Tenant.

          An otherwise valid exercise of the Second Renewal Option shall be
          fully effective whether or not the Second Renewal Amendment is
          executed.

III. CONDITIONAL RIGHT OF FIRST OFFER.
     ---------------------------------

     A.   During the period beginning on the Commencement Date, Tenant shall
          have the "Right of First Offer" with respect to any space that becomes
          Available for Lease (hereinafter defined) in Two Riverside Center and
          Three Riverside Center (the "Offering Space"). Such Right of First
          Offer, however, shall only be applicable with respect to space in Two
          Riverside Center and Three Riverside Center that either: (i) has been
          previously leased by Landlord to a third party (the "Original Third
          Party Tenant") and such lease with an Original Third Party Tenant
          being referred to as a "Third Party Lease"), or (ii) has not been
          leased by Landlord within twenty-four (24) full calendar months
          following the Commencement Date ("Unleased Space"). Leases or license
          agreements that are entered into by Landlord for storage purposes or
          as temporary space while a third party's permanent space is being
          constructed shall not be a Third Party Lease for the purposes hereof.
          Offering Space that has been leased to an Original Third Party Tenant
          shall be deemed to be "Available for Lease" when Landlord has
          determined that (w) the Original Third Party Tenant leasing the
          Offering Space or portion thereof will not extend or renew the term of
          its lease for the Offering Space or portion thereof (but in any event
          not later than the first to occur of (i) 90 days after the expiration
          of any renewal or extension option (if applicable) in a Third Party
          Lease that was not exercised by the tenant thereunder, or (ii) the
          expiration of the term of the Third Party Lease), and (x) all Superior
          Rights (hereinafter defined) with respect to such portion of the
          Offering Space have lapsed or been waived. Offering Space that is
          considered to be Unleased Space shall be deemed to be "Available for
          Lease" when Landlord has determined that (y) Landlord has not entered
          into a lease for such Offering Space within twenty-four (24) full
          calendar months following the Commencement Date, and (z) all Superior
          Rights (hereinafter defined) with respect to such portion of the
          Offering Space have lapsed or been waived.

          Within a reasonable time after Landlord has determined that a
          particular portion of the Offering Space is Available for Lease (but
          prior to leasing such portion of the Offering Space to a third party
          other than the Original Third Party Tenant or a party with Superior
          Rights), Landlord shall advise Tenant (the "Advice") of the square
          footage and location of such portion of the Offering Space and the
          terms (i.e. Base Rent and Additional Rent) under which Landlord is
          prepared to lease such Offering Space to Tenant for the remainder of
          the Term, which terms shall reflect the Prevailing Market (hereinafter
          defined) rate for such Offering Space as reasonably determined by
          Landlord. Tenant may lease such portion of the Offering Space in its
          entirety only, under such terms, by delivering written notice of
          exercise to Landlord ("Notice of Exercise") within 10 days after the
          date of the Advice. In the event that separate leases of Offering
          Space expire simultaneously, the premises under each expiring lease
          shall be considered to be a separate parcel of Offering Space that
          must be separately offered to Tenant in accordance with the terms
          hereof.

          Notwithstanding anything herein to the contrary, Tenant shall have no
          such Right of First Offer and Landlord need not provide Tenant with an
          Advice, if:

          1.   Tenant is in default under the Lease beyond any applicable notice
               and cure periods at the time Landlord would otherwise deliver the
               Advice; or

          2.   more than fifteen percent (15%) of the Premises is sublet (except
               in connection with a Permitted Transfer) at the time Landlord
               would otherwise deliver the Advice; or

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<PAGE>   58

          3.   the Lease has been assigned (except in connection with a
               Permitted Transfer) prior to the date Landlord would otherwise
               deliver the Advice; or

          4.   the Offering Space is not intended for the exclusive use of
               Tenant during the Term; or

          5.   the Offering Space is not Available for Lease, meaning that (i)
               the Original Third Party Tenant is interested in extending or
               renewing its lease for the Offering Space or entering into a new
               lease for such Offering Space, or (ii) the Offering Space is
               subject to Superior Rights.

     B.   1.   The term for the Offering Space shall commence upon the
               commencement date stated in the Advice (provided that full
               possession of the Offering Space is delivered to Tenant) and
               expire on the Termination Date. Upon commencement, such Offering
               Space shall be considered a part of the Premises, provided that
               all of the terms stated in the Advice shall govern Tenant's
               leasing of the Offering Space and only to the extent that they do
               not conflict with the Advice, the terms and conditions of this
               Lease shall apply to the Offering Space.

          2.   Tenant shall pay Base Rent and Additional Rent for the Offering
               Space in accordance with the terms and conditions of the Advice,
               which terms and conditions shall reflect the Prevailing Market
               rate for the Offering Space as determined in Landlord's
               reasonable judgment.

          3.   The Offering Space (including improvements and personalty, if
               any) shall be accepted by Tenant in its condition and as-built
               configuration existing on the earlier of the date Tenant takes
               possession of the Offering Space or as of the date the term for
               such Offering Space commences, provided that such Offering Space
               shall be delivered to Tenant in broom clean condition and free of
               claims and possession of third parties.

     C.   1. TERMINATION OF RIGHT OF FIRST OFFER WITH RESPECT TO SPECIFIC
          OFFERING SPACE. The rights of Tenant hereunder with respect to any
          portion of the Offering Space for which is Available for Lease shall
          terminate on the earlier to occur of: (i) Tenant's failure to exercise
          its Right of First Offer within the 10 day period provided in
          paragraph A above, and (ii) the date Landlord would have provided
          Tenant an Advice if Tenant had not been in violation of one or more of
          conditions (1) through (4) set forth in Paragraph A above.
          Notwithstanding the foregoing, if (i) Tenant was entitled to exercise
          its Right of First Offer, but failed to provide Landlord with a Notice
          of Exercise within the 10 day period provided in paragraph A above,
          and (ii) Landlord does not enter into a lease for such portion of the
          Offering Space within a period of 9 months following the date of the
          Advice, Tenant shall once again have a Right of First Offer in
          accordance with this Section III with respect to such portion of the
          Offering Space. In addition, Tenant shall once again have the Right of
          First Offer with respect to such Offering Space if, within such 9
          month period, Landlord proposes to lease the Offering Space to a
          prospective tenant on terms that are substantially different than
          those set forth in the Advice. For purposes hereof, the terms offered
          to a prospect shall be deemed to be substantially the same (i.e. not
          different) as those set forth in the Advice as long as there is no
          more than a 5% reduction in the "bottom line" cost per rentable square
          foot of the Offering Space to the prospect when compared with the
          "bottom line" cost per rentable square foot under the Advice,
          considering all of the economic terms of the both deals, respectively,
          including, without limitation, the length of term, the net rent, any
          tax or expense escalation or other financial escalation, brokerage
          commissions and any construction allowance, improvement allowance or
          other financial concessions.

          2. TERMINATION OF RIGHT OF FIRST OFFER WITH RESPECT TO ALL OFFERING
          SPACE. Tenant's Right of First Offer shall terminate as follows: (i)
          if Tenant fails to provide Landlord with an Initial First Renewal
          Notice, Tenant's Right of First Offer shall terminate as of the last
          day on which Tenant was entitled to provide such Initial First Renewal
          Notice; (ii) if Tenant provides Landlord with an Initial First Renewal
          Notice but fails to provide Landlord with a First Binding Notice,
          Tenant's Right of First Offer shall terminate as of the last day on
          which Tenant was entitled to provide such First Binding Notice; (iii)
          if the Lease is effectively extended for the

                                       6
<PAGE>   59

          First Renewal Term and Tenant fails to provide Landlord with an
          Initial Second Renewal Notice, Tenant's Right of First Offer shall
          terminate as of the last day on which Tenant was entitled to provide
          such Second Renewal Notice; (iv) if the Lease is effectively extended
          for the First Renewal Term and Tenant provides Landlord with an
          Initial Second Renewal Notice but fails to provide Landlord with a
          Second Binding Notice, Tenant's Right of First Offer shall terminate
          as of the last day on which Tenant was entitled to provide such Second
          Binding Notice; and (v) if the Lease is effectively extended for the
          Second Renewal Term, Tenant's Right of First Offer shall terminate on
          the second anniversary of the commencement of the Second Renewal Term.

          3. ADDITIONAL CONDITION TO RIGHT OF FIRST OFFER If Landlord provides
          Tenant with an Advice during the initial 10 year Term on a date that
          is subsequent to the seventh (7th) anniversary of the Commencement
          Date: (i) the proposed term for the Offering Space shall run until the
          end of the First Renewal Term, and (ii) Tenant must concurrently
          exercise (or have previously exercised) its First Renewal Option as a
          condition to its exercise of its Right of First Offer. If Landlord
          provides Tenant with an Advice during the First Renewal Term on a date
          that is subsequent to the second (2nd) anniversary of the First
          Renewal Term: (i) the proposed term for the Offering Space shall run
          until the end of the Second Renewal Term, and (ii) Tenant must
          concurrently exercise (or have previously exercised) its Second
          Renewal Option as a condition to its exercise of its Right of First
          Offer.

     D.   If Tenant is entitled to and properly exercises its Right of First
          Offer, Landlord shall prepare an amendment (the "Offering Amendment")
          to reflect changes in the Base Rent, Rentable Square Footage of the
          Premises, Tenant's Pro Rata Share and other appropriate terms. The
          Offering Amendment shall be:

          1.   sent to Tenant within a reasonable time after receipt of the
               Notice of Exercise; and

          2.   revised by Landlord to address any requested changes by Tenant
               that are reasonably necessary to accurately reflect the terms and
               conditions hereof; and

          3.   executed by Tenant and returned to Landlord within fifteen (15)
               days after such Offering Amendment (together with such changes
               described in the immediately preceding paragraph) is delivered to
               Tenant by Landlord who shall promptly countersign the same and
               return a fully executed counterpart to Tenant.

          An otherwise valid exercise of the Right of First Offer shall be fully
          effective whether or not the Offering Amendment is executed.

     E.   For purposes hereof:

          1.   "Prevailing Market" shall mean the arms length fair market annual
               base rental rate per rentable square foot, as determined in
               Landlord's reasonable judgment, under leases and expansion
               amendments entered into on or about the date on which the
               Prevailing Market is being determined hereunder for space
               comparable to the Offering Space in the Building. The
               determination of Prevailing Market Base Rent rate shall take into
               account any material economic differences between the fixed terms
               of the Lease with respect to the Offering Space (e.g. the Term,
               Tax Base Year and Expense Base Year) and the leases and expansion
               amendments that are being used for comparison purposes,
               including: (i) the value of any economic concessions (e.g rental
               abatements, refurbishment allowances); (ii) the difference (on a
               rentable square foot basis) between any broker commissions
               payable by Landlord in connection with the Offering Space and any
               brokerage commissions payable by Landlord with respect to a
               comparison lease or amendment; and (iii) the differences in the
               way Landlord is reimbursed for operating expenses and taxes. The
               determination of Prevailing Market shall also take into
               consideration any reasonably anticipated changes in the
               Prevailing Market rate from the time such Prevailing Market rate
               is being determined and the time such Prevailing Market Base Rent
               rate will become effective under this Lease. Notwithstanding
               anything herein to the contrary, if any comparison lease or
               amendment provides for an improvement allowance or refurbishment
               allowance, the effect of such allowance on the Prevailing Market
               rate shall be determined by comparing the rental value of the
               Offering Space in its "as-is" condition against the actual or
               anticipated rental value of the comparison premises after such
               premises have been improved by the expenditure of the improvement
               allowance or refurbishment allowance. An example of how such
               concept will be applied is set forth in Section I of this

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<PAGE>   60

               Exhibit E.

          2.   "Superior Rights" shall mean the following with respect to Two
               Riverside Center and Three Riverside Center:

               a.   Two Riverside Center - Landlord shall be entitled to grant
                    up to 10,000 square feet of fixed expansion rights for space
                    in Two Riverside Center that are superior to Tenant's
                    Conditional Right of First Offer. For purposes hereof, the
                    term "fixed expansion rights" shall refer to the option of a
                    third party to lease space in Two Riverside Center, the
                    exercise of which is not contingent upon the space first
                    being available for lease or first being offered for lease
                    to another party. A fixed expansion right may be applicable
                    to either specifically identified space or space to be
                    identified at a later date. Likewise, the effective date
                    under a fixed expansion right may be a date certain or a
                    date to be determined. By way of example, Tenant's First
                    Expansion Option and Second Expansion Option would be
                    considered to be a fixed expansion option. Tenant's
                    Conditional Right of First Offer, on the other hand, would
                    not be considered to be a fixed expansion option.

               b.   Three Riverside Center - Tenant's Conditional Right of First
                    Offer shall be subject and subordinate to the right of first
                    offer granted to Harvard Vanguard Medical Associates, Inc.
                    ("Harvard") for space in Three Riverside Center, regardless
                    of whether a lease with Harvard is executed subsequent to
                    the execution of this Lease. In addition, Landlord shall be
                    entitled to grant up to 20,000 square feet of fixed
                    expansion rights for space in Three Riverside Center that
                    are superior to Tenant's Conditional Right of First Offer.
                    Such 20,000 square foot amount shall be inclusive of all
                    space that is encumbered by any fixed expansion rights
                    granted to Harvard.

IV.  FIRST EXPANSION OPTION.
     -----------------------

     A.   Tenant shall have the option (the "First Expansion Option") to lease
          the 32,152 rentable square feet of space on the third (3rd) floor of
          Two Riverside Center as shown on Exhibit P attached hereto (the "First
          Expansion Space"). Tenant acknowledges that the First Expansion Space
          may be delivered to Tenant in up to two parcels, provided that (i) the
          delivery of the last parcel of First Expansion Space shall occur no
          later than nine (9) months after the deliver of the first parcel of
          First Expansion Space, and (ii) no single parcel of First Expansion
          Space shall contain less than 5,000 rentable square feet of space.
          Tenant's right to exercise its First Expansion Option shall be subject
          to the following conditions:

          1.   Landlord receives written notice (the "First Expansion Notice")
               from Tenant of the exercise of its First Expansion Option on or
               before the last day of the sixty-ninth (69th) full calendar month
               of the Lease Term; and

          2.   Tenant is not in default under this Lease beyond any applicable
               notice and cure periods at the time Landlord receives the First
               Expansion Notice; and

          3.   no more than fifteen percent (15%) of the Premises is sublet
               (except in connection with a Permitted Transfer) at the time
               Landlord receives the First Expansion Notice; and

          4.   this Lease has not been assigned (except in connection with a
               Permitted Transfer) prior to the time Landlord receives the First
               Expansion Notice; and

          5.   the First Expansion Space is intended for the exclusive use of
               Tenant only during the Term.

     B.   1. The initial annual Base Rent rate per square foot for the First
          Expansion Space shall equal the Prevailing Market rate per rentable
          square foot for the First Expansion Space as defined in Section III.E
          above, provided that any references to the Offering Space in Section
          III.E. shall be deemed to refer to the First Expansion Space. Base
          Rent attributable to the First Expansion Space shall be payable in
          monthly installments in accordance with the terms and conditions of
          Article IV of the Lease. Within 30 days after receipt of Tenant's
          First Expansion Notice, Landlord shall advise Tenant of the size and
          location of the First Expansion Space, the date the First Expansion
          Space will be available for occupancy and the applicable

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<PAGE>   61

          Prevailing Market Base Rent rate for the First Expansion Space (the
          "Prevailing Market Notice"), provided in no event shall Landlord be
          required to provide Tenant with a Prevailing Market Notice more than
          twelve (12th) months prior to the date on which the First Expansion
          Space will be available for occupancy by Tenant. If Tenant, in its
          reasonable judgment, determines that the rate set forth in Landlord's
          Prevailing Market Notice does not accurately reflect the Prevailing
          Market Base Rent rate for the First Expansion Space, Tenant shall
          provide Landlord with written notice of rejection (the "Expansion
          Space Rejection Notice") within 15 days after the date of Landlord's
          Prevailing Market Notice. If Tenant provides Landlord with an
          Expansion Space Rejection Notice within such 15 day period, Landlord
          and Tenant shall work together in good faith to determine the
          Prevailing Market Base Rent rate for the First Expansion Space.
          Notwithstanding the foregoing, if Landlord and Tenant fail to agree
          upon the Prevailing Market Base Rent rate for the First Expansion
          Space within 30 days after the date of the Expansion Space Rejection
          Notice, Tenant shall have the option to withdraw its First Expansion
          Notice by giving Landlord written notice of such withdrawal within 10
          days after the expiration of such 30 day period. If Tenant elects to
          withdraw (or is deemed to have withdrawn) its First Expansion Notice,
          Tenant's right to lease the First Expansion Space shall be null and
          void and of no further force and effect. If Landlord and Tenant cannot
          agree upon Prevailing Market Base Rent rate within the 30 day period
          described above and, in addition, the First Expansion Notice is not
          withdrawn, the Prevailing Market Base Rent rate for the First
          Expansion Space shall be determined by an exchange of Estimates or by
          binding arbitration in accordance with the procedures described in
          Section I for the determination of the Prevailing Market Base Rent
          rate for the Renewal Term, provided, that, the determination of the
          Prevailing Market Base Rent shall take into account that the term of
          the First Expansion Space is an initial term and not a renewal or
          extension term. Notwithstanding anything herein to the contrary, the
          determination of the Prevailing Market Base Rent shall take into
          account the Additional Rent that Tenant is required to pay in
          Subsection IV.B.2. below.

          2. Tenant shall pay Additional Rent (i.e. Tenant's Pro Rata Share of
          Expense Excess and Tenant's Pro Rata Share of Tax Excess) for the
          First Expansion Space on the same terms and conditions set forth in
          Article IV this Lease, including the Tax Base Year and Expense Base
          Year. Tenant's Pro Rata Share shall increase appropriately to account
          for the addition of the First Expansion Space.

     C.   The term for the First Expansion Space shall commence on the date
          Landlord provides Tenant with full possession of the First Expansion
          Space (or the applicable parcel thereof) in its entirety for the
          purpose of allowing Tenant to occupy the First Expansion Space for the
          Permitted Use or for the performance of improvements therein. Subject
          to causes beyond Landlord's control (e.g. a holdover by a then
          existing tenant), Landlord agrees to provide Tenant with full
          possession of the First Expansion Space (or the applicable parcel
          thereof) upon the day following the expiration date of the First
          Expansion Lease (hereinafter defined) for such First Expansion Space
          or portion thereof. For purposes hereof, the term "First Expansion
          Lease" shall mean a lease for the First Expansion Space, or portion
          thereof, that is entered by and between Landlord and a third party
          tenant. Landlord shall not enter into any First Expansion Leases that
          have a term in excess of seven (7) years (including renewals and
          extensions) unless Landlord reserves the right to relocate such third
          party or terminate such First Expansion Lease on or before the last
          day of the seventh (7th) year of such First Expansion Lease. The term
          for the First Expansion Space shall expire on the Termination Date.
          Upon the commencement of the term for the First Expansion Space, or
          applicable portion thereof, the First Expansion Space shall be
          considered Premises, subject to all the terms and conditions of this
          Lease, except that no allowances, credits, abatements or other
          concessions (if any) set forth in this Lease for the initial Premises
          shall apply to the First Expansion Space. If Tenant does not provide
          Landlord with an First Expansion Notice on or before the date set
          forth above or if Tenant is not entitled to exercise its First
          Expansion Option due to a violation of one of the conditions set forth
          in paragraph A above, Tenant's First Expansion Option shall be deemed
          to be null and void and Tenant shall have no further rights to lease
          the First Expansion Space hereunder.

     D.   If Tenant is entitled to and properly exercises the First Expansion
          Option, Landlord shall prepare an amendment (the "First Expansion
          Amendment") to reflect the commencement date(s) of the term for the
          First Expansion Space and the changes in Base Rent, Rentable Square
          Footage of the Premises, Tenant's Pro Rata Share

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<PAGE>   62

          and other appropriate terms. The First Expansion Amendment shall be:

          1.   sent to Tenant within a reasonable time after receipt of the
               First Expansion Notice; and

          2.   revised by Landlord to address any requested changes by Tenant
               that are reasonably necessary to accurately reflect the terms and
               conditions hereof; and

          3.   executed by Tenant and returned to Landlord within fifteen (15)
               days after such First Expansion Amendment (together with such
               changes described in the immediately preceding paragraph) is
               delivered to Tenant by Landlord who shall promptly countersign
               the same and return a fully executed counterpart to Tenant.

          An otherwise valid exercise of the First Expansion Option shall be
          fully effective whether or not the First Expansion Amendment is
          executed.

V.   INTENTIONALLY OMITTED.
     ----------------------

VI.  PARKING.
     --------

     A.   During the initial Term, Landlord shall make parking spaces available
          to Tenant at the Property based on a ratio of 3 parking spaces per
          1,000 rentable square feet of Premises leased by Tenant from time to
          time (the "Parking Ratio"). Tenant acknowledges that handicapped
          parking spaces and visitor parking spaces are included within the
          Parking Ratio of 3 spaces per 1,000 rentable square feet. In other
          words, Tenant's Pro Rata Share of the total amount of visitor and
          handicapped parking spaces for the entire Property shall be deducted
          from the number of parking spaces that Tenant is entitled to use based
          on the Parking Ratio. Landlord, in its sole discretion, shall have the
          right to allocate Tenant's parking rights between the surface parking
          areas, the parking structure and the executive parking garage beneath
          One Riverside Center (collectively referred to at the "Parking
          Areas"), provided that not less than 69 of Tenant's parking spaces
          (exclusive of handicapped parking spaces) shall be located in the
          executive parking garage beneath the Building. As of the date hereof,
          it is contemplated that Tenant's parking spaces will be allocated as
          follows: 573 spaces in the parking structure, 169 spaces in the
          surface parking areas and 69 spaces in the executive parking garage.
          Tenant shall not have the right to lease or otherwise use more than
          its share of parking spaces. Landlord shall have the right to
          establish such rules and regulations as Landlord reasonably elects to
          monitor the use of parking spaces by Tenant and other tenants,
          visitors and invitees and to assure, to the extent reasonably
          possible, that such parties are parking in the specific areas (e.g.
          surface areas, parking structure or garage) designated by Landlord and
          Tenant is not exceeding the Parking Ratio. Without limitation,
          Landlord shall have the right to implement a system of parking passes,
          parking stickers, card key access or any other system reasonably
          designated by Landlord. Tenant shall be responsible for assuring that
          its visitors, employees, subtenants and invitees comply with the rules
          and regulations designated by Landlord. Landlord shall have the right
          to require Tenant to institute and operate a subsidized MBTA pass
          program at the Premises to encourage Tenant's employees to use public
          transportation.

      B.  Landlord shall have the right to institute a parking management
          program (the "Program") to monitor and enforce the use of parking
          spaces by Tenant, the other tenants and occupants of the Building and
          their respective employees and guests. Without limitation, the Program
          may provide for: (i) the imposition of uniform fines to tenants
          (including Tenant) and occupants whose use of the Parking Areas
          exceeds the Parking Ratio on any given day; (ii) the implementation of
          an automated or manually operated access system that would prohibit a
          vehicle of a specific tenant or occupant (including their respective
          employees) from entering all or a particular portion of the Parking
          Areas at any time during which the tenant is using parking spaces in
          excess of the Parking Ratio; (iii) the implementation of a system
          where all or a portion of each tenant's spaces are designated as
          reserved spaces, provided that any such system will

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<PAGE>   63

          be implemented in such a way as to not discriminate against Tenant
          with respect to the number of spaces at are designated as reserved
          (based on a percentage of the total spaces) and the location of such
          reserved spaces; (iv) the implementation of a system where all or a
          portion of the parking spaces are designated as valet park spaces; (v)
          the implementation of a system where tenants and occupants are
          required to display parking stickers for the use of all or any portion
          of the Parking Areas; and/or (vi) the implementation of a system for
          towing the vehicles of specific tenants or occupants (including their
          respective employees) that are in violation of any terms of the
          Program, including, without limitation, the provisions of the Program
          with respect to the Parking Ratio, reserved parking areas, parking
          stickers, handicapped and visitor parking and card access. All towing
          shall be done without any liability to Landlord and at the sole risk,
          cost, expense and liability of the vehicle owner and the tenant or
          occupant that employs the vehicle owner. In is agreed that Tenant
          shall be deemed to be in violation of the Parking Ratio if Tenant
          exceeds the Parking Ratio as a whole with respect to all available
          spaces or exceeds the applicable number of spaces that is designated
          as to a particular portion of the Parking Area (i.e. surface parking
          areas, parking structure and the executive parking garage). Landlord
          shall have the right, in its sole discretion, to designate the rules,
          regulations and terms of the Program and to change the rules,
          regulations and terms from time to time. Notwithstanding the
          foregoing, Landlord agrees to use reasonable efforts to enforce the
          Program in manner that does not discriminate against any individual
          tenant or group of tenants. In addition, Landlord shall be obligated
          to provide Tenant with written notice of the rules, regulations and
          terms of the Program, including any changes to the Program that are
          enacted from time to time.

     C.   During the initial Term, Tenant shall not be required to pay Landlord
          for the right to use the designated Parking Areas and spaces.
          Thereafter, Tenant shall be required to pay the prevailing market rate
          (if any) for parking. The cost of maintaining, operating and repairing
          the Parking Areas shall, however, be considered an Expense. If during
          any renewal Term, Tenant shall pay for parking, the cost of
          maintaining, operating and repairing the Parking Areas shall be
          excluded from Expenses.

     D.   Except for particular spaces and areas designated by Landlord for
          reserved parking, all parking in the Parking Areas shall be on an
          unreserved, first-come, first-served basis.

     E.   Landlord shall not be responsible for money, jewelry, automobiles or
          other personal property lost in or stolen from the Parking Areas
          regardless of whether such loss or theft occurs when the Parking Areas
          or other areas therein are locked or otherwise secured. Except as
          caused by the negligence or willful misconduct of Landlord and without
          limiting the terms of the preceding sentence, Landlord shall not be
          liable for any loss, injury or damage to persons using the Parking
          Areas or automobiles or other property therein, it being agreed that,
          to the fullest extent permitted by law, the Parking Areas shall be
          used at the sole risk of Tenant and its employees.

     F.   Landlord shall have the right from time to time to designate
          reasonable rules and regulations regarding the Parking Area and the
          use thereof, including, but not limited to, rules and regulations
          controlling the flow of traffic to and from various parking areas, the
          angle and direction of parking, the hours during which cars can be
          parked on the roof of the garage and the like. Tenant shall comply
          with and cause its employees to comply with all such rules and
          regulations as well as all reasonable additions and amendments
          thereto.

     G.   Tenant shall not store or permit its employees to store any
          automobiles in the Parking Areas without the prior written consent of
          Landlord. Except for emergency repairs, Tenant and its employees shall
          not perform any work on any automobiles while located in the Parking
          Areas. If it is necessary for Tenant or its employees to leave an
          automobile in the Parking Areas overnight, Tenant shall provide
          Landlord with prior notice thereof designating the license plate
          number and model of such automobile.

     H.   Landlord shall have the right upon reasonable prior notice (except in
          the event of an emergency) to temporarily close portions of the
          Parking Areas in order to

                                       11
<PAGE>   64

          perform necessary repairs, maintenance and improvements to the Parking
          Areas. In such event, Landlord shall use reasonable efforts to make
          substitute parking available.

     I.   Tenant shall be required to use reasonable efforts to comply with the
          provisions of the Program, paragraphs F and G above and the other
          terms of this Section. Tenant's failure to comply, however, shall not
          be considered to be a default under the Lease unless Tenant's conduct
          is materially detrimental to the operation of the Building. Landlord
          shall, however, be entitled to exercise all of its rights and remedies
          provided under the Program, including, without limitation, towing
          vehicles. In addition, if any individual violates the terms of the
          Program on more than 3 occasions in any 12 month period, Landlord
          shall have the right to cause Tenant to terminate and reassign the
          parking privileges of such individual.

VII. HAZARDOUS MATERIALS.
     --------------------

     A.   Except as disclosed hereby, Landlord represents, to the best of its
          knowledge, that the Premises will on the Commencement Date be free of
          Hazardous Materials (as defined below) in amounts that violate
          applicable Laws, and that Landlord, at Landlord's sole cost and
          expense following notice of any violation, will cause the Premises to
          be in full compliance with any and all applicable Laws relating to
          asbestos, PCB's and other Hazardous Materials. Notwithstanding the
          foregoing, Tenant, at its sole cost and expense, shall be responsible
          for correcting any violations of applicable Laws with respect to any
          asbestos, PCB's and other Hazardous Materials that are introduced into
          the Building or Premises by Tenant or any Tenant Related Parties.
          Tenant shall not use, generate, manufacture, store or dispose of, on
          or about the Premises, or transport to or from the Premises, any
          flammable explosives, radioactive materials, hazardous wastes, toxic
          substances, or any related materials or substances, including, without
          limitation, any substance defined as or included in the definition of
          "hazardous substances" under any applicable federal, state or local
          law, regulation or ordinance (collectively, "Hazardous Materials").

     B.   Notwithstanding the provisions of Subsection VII.A above, Tenant and
          Landlord shall have the right to use and store on the Premises and the
          Building, and transport to and from the Premises and the Building,
          those Hazardous Materials which are generally used in the ordinary
          course in first class office buildings (collectively, "Permitted
          Materials"); provided, however, that such party's use, storage and
          transport thereof is in compliance with all applicable Laws.

     C.   Landlord agrees to defend, fully indemnify, and hold entirely free and
          harmless Tenant from and against all claims, judgments, damages,
          penalties, fines, costs, liabilities, or losses (including, without
          limitation, sums paid in settlement of claims, attorneys' fees,
          consultant fees, and expert fees) which arise before, during or after
          the Term and which are imposed on, paid by, or asserted against Tenant
          by reason of the presence or suspected presence of Hazardous Materials
          in the soil, groundwater, or soil vapor on or about the Premises,
          except to the extent that the Hazardous Material is present as a
          result of Tenant's activities on the Premises.

     D.   Tenant agrees to defend, fully indemnify, and hold entirely free and
          harmless Landlord from and against all claims, judgments, damages,
          penalties, fines, costs, liabilities, or losses (including, without
          limitation, sums paid in settlement of claims, attorneys' fees,
          consultant fees, and expert fees) which arise during or after the Term
          and which are imposed on, paid by, or asserted against Landlord by
          reason of the presence or suspected presence of Hazardous Materials in
          the soil, groundwater, or soil vapor on or about the Premises to the
          extent that the Hazardous Material is present as a result of Tenant's
          activities on the Premises during the Term.

     E.   Notwithstanding anything in this Lease to the contrary, in no event
          shall any Mortgagee (defined in Subsection XXVI.A. of the Lease) be
          liable for any of the obligations of Landlord under Subsection VII.C.
          above.

     F.   Notwithstanding anything in this Lease to the contrary, Tenant shall
          not be responsible under this Lease in any respect whatsoever for any
          condition involving

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<PAGE>   65

          Hazardous Materials on or about the Premises, the Building or the land
          thereunder, except to the extent resulting from Tenant's activities.

VIII. MONUMENT SIGN.
      --------------

     A.   Tenant shall have the right to be identified on a multi-tenant
          monument sign installed by Landlord, if any, on the exterior grounds
          of the Property (the "Monument Sign"), if: (1) Landlord is entitled to
          install the Monument Sign; and (2) at the time the Monument Sign is
          installed, Tenant is not in violation of any of the Monument Signage
          Conditions. Landlord shall be responsible for obtaining any applicable
          governmental approvals for the Monument Sign. If Landlord elects to
          install more than one (1) Monument Sign, Tenant shall only be entitled
          to be identified on one (1) Monument Sign. Landlord shall have the
          right to designate the Monument Sign on which Tenant will be
          identified, provided that Landlord shall use reasonable efforts to
          give Tenant identity on the Monument Sign closest to the entrance of
          One Riverside Center. Tenant acknowledges that there are no guaranties
          that Landlord will obtain any necessary approvals to install a
          Monument Sign and that Landlord's and Tenant's efforts to obtain
          approval to install other Tenant signs described herein might conflict
          with Landlord's efforts to attempt to obtain approval for the Monument
          Sign. Tenant further acknowledges that Landlord does not currently
          intend to install or attempt to obtain approval for a multi-tenant
          Monument Sign, but, instead, will seek approval for a monument sign
          that lists the name and address of the Building, as well as the name
          "Equity Office" or "Equity Office Properties".

     B.   All costs in connection with the initial design, fabrication and
          installation of the Monument Sign shall be borne by Landlord. All
          costs in connection with the design, fabrication and installation of
          any Tenant identification on the Monument Sign (the "Tenant
          Identification") shall be borne by Tenant. Tenant shall submit to
          Landlord reasonably detailed drawings of the proposed Tenant
          Identification, including without limitation, the size, material,
          shape and lettering for review and approval by Landlord.
          Notwithstanding the foregoing, Landlord shall have the right to
          designate standard sizes, materials, shapes and lettering for any
          tenant identification on the Monument Sign, which standards may differ
          depending on the square footage of the tenant that is being identified
          on the Monument Sign. Tenant shall reimburse Landlord for any costs
          associated with Landlord's review of the Tenant Identification. Tenant
          will be responsible for the repair and maintenance of the Tenant
          Identification and for Tenant's proportionate share of any costs
          incurred by Landlord to maintain and repair the Monument Sign. Such
          proportionate share shall be determined based on the number of tenants
          that are identified on the Monument Sign from time to time. Landlord,
          upon the expiration date or sooner termination of this Lease, shall
          have the right to remove the Tenant Identification. In addition,
          Landlord shall have the right to remove the Tenant Identification, if,
          at any time during the Lease Term, Tenant is in violation of any of
          the Monument Signage Conditions. For purposes hereof, the "Monument
          Signage Conditions" are: (1) Tenant has not assigned this Lease
          (except in connection with a Permitted Transfer), (2) Tenant has not
          sublet more than 35% of the Premises (except in connection with a
          Permitted Transfer), (3) Tenant and any Permitted Transferee are using
          at least 65% of the Premises for the Permitted Use, (4) Tenant is not
          in default under any term or condition of the Lease after the delivery
          of notice and the expiration of any applicable cure periods.
          Notwithstanding the foregoing, if the Monument Sign is a
          "multi-tenant" monument sign (i.e. it includes the name of at least
          one (1) tenant in addition to Tenant), condition (1) prohibiting an
          assignment of the Lease shall not be applicable and an assignee of
          Tenant's interest under the Lease shall be entitled to substitute its
          name for the name of Tenant on the Monument Sign. The name of Landlord
          or its managing agent shall not be considered to be a tenant name for
          the purpose of determining whether the Monument Sign is a multi-tenant
          monument sign.

IX.  DIRECTORY AND ENTRY SIGNAGE.
     ----------------------------

     A.   Tenant shall have the right to install, at its sole cost and expense,
          signage in the atrium of the Building over the entrance to One
          Riverside Center, the approximate size, design and location of which
          shall be in accordance with Exhibit O hereto (the "Atrium Sign"). All
          costs in connection with the Atrium Sign, including any costs for the
          design, installation, supervision of installation, wiring,
          maintenance, repair and

                                       13
<PAGE>   66
          removal of the Atrium Sign, will be at Tenant's expense. Except to the
          extent previously submitted to and approved by Landlord, Tenant shall
          submit to Landlord reasonably detailed drawings of the proposed Atrium
          Sign, including without limitation, the size, material, shape and
          lettering for review and approval by Landlord, which approval Landlord
          agrees not to withhold to the extent that such drawings are consistent
          with Exhibit O. The Atrium Sign shall conform to the standards of
          design and motif established by Landlord for the exterior of the
          Building and the Property on which it is located. Tenant shall
          reimburse Landlord for any costs associated with Landlord's review and
          supervision as hereinbefore provided including, but not limited to,
          engineers and other professional consultants. Tenant will be
          responsible for the repair of any damage that the installation of the
          Atrium Sign may cause to the Building or Property. Tenant agrees upon
          the expiration date or sooner termination of this Lease, upon
          Landlord's request, to remove the Atrium Sign and to repair and
          restore any damage to the Building and Property at Tenant's expense.
          In addition, Landlord shall have the right to remove the Atrium Sign
          at Tenant's sole cost and expense, if, at any time during the Lease
          Term: (1) Tenant sublets more than 35% of the Premises (except in
          connection with a Permitted Transfer), (2) Tenant and any Permitted
          Transferee cease to occupy at least 65% of the Premises, or (3) Tenant
          defaults under any term or condition of the Lease and fails to cure
          such default within any applicable grace period. An assignee of
          Tenant's entire interest under this Lease shall be entitled to
          substitute its name for the name of Tenant on such Atrium Sign,
          provided that such replacement Atrium Sign shall be subject to the
          same approval process set forth herein for the original Atrium Sign.

     B.   Landlord shall provide and install, at Landlord's cost, any Building
          standard suite numbers and Building standard Tenant identification
          signage on or adjacent to the main entry door to the Premises on each
          floor on which the Premises are located. Notwithstanding the
          foregoing, Tenant, at its sole cost and expense, shall have the right
          to install additional custom signage identifying Tenant on any full
          floors leased by Tenant, provided that such signage is not visible
          from outside the Building. Tenant shall also be entitled to its
          proportionate share of lines on the main building directory. Tenant
          shall not be charged a fee for the initial installation of any names
          on the Building directory. Tenant shall, however, be required to pay
          Landlord's then standard fee (which fee must be reasonable) for any
          additional names to be added to the Building directory or any
          replacement of previously existing names.

X.   PARKING STRUCTURE SIGNAGE.
     --------------------------

     A.   Provided that Landlord is able to obtain all necessary building
          permits and zoning, regulatory and governmental approvals, Tenant
          shall have the right to install one (1) exclusive sign identifying
          Tenant on the side wall of the top level of the structured parking
          facility (the "Parking Structure Sign"). The approximate location and
          size of the Parking Structure Sign is shown on Exhibit K hereto.
          Tenant's right to install the Parking Structure Sign shall, however,
          be subject to the satisfaction of all of the Parking Signage
          Conditions (defined in subsection X.B. below). The application for the
          Parking Structure Sign shall be made as part of a joint application
          for all requests for signage at the Building. In the event that
          Landlord's joint application for signage is not approved, Landlord
          shall work with Tenant and any other tenants represented in such
          application to agree upon an alternative signage plan that is
          reasonably acceptable to all parties and to the City of Newton.
          Landlord shall have the right to retain legal counsel and consultants
          to represent the joint interests of Tenant, Landlord and any other
          tenants who have been granted signage rights and Tenant agrees to pay
          its proportionate share of such costs based on the number of signs for
          which approval is being requested. Tenant acknowledges that Landlord
          cannot guaranty that Tenant will receive the necessary permits and
          approvals to allow Tenant to install the Parking Structure Sign.
          Landlord, however, shall diligently advocate approval of the proposed
          signage plan for the Building. Tenant agrees to use reasonable efforts
          to complete its specifications for the proposed Parking Structure Sign
          so as to allow a joint signage application to be submitted for
          approval in January, 2000 (or earlier if reasonably possible).

     B.   All costs in connection with the Parking Structure Sign, including any
          costs for the design, installation, supervision of installation,
          wiring, maintenance, repair and removal of the Parking Structure Sign,
          will be at Tenant's expense. Tenant shall submit to Landlord
          reasonably detailed drawings of the proposed Parking

                                       14
<PAGE>   67

          Structure Sign, including without limitation, the size, material,
          shape and lettering for review and approval by Landlord. The Parking
          Structure Sign shall conform to the standards of design and motif
          established by Landlord for the exterior of the Building and the
          Property on which it is located. Tenant shall reimburse Landlord for
          any costs associated with Landlord's review and supervision as
          hereinbefore provided including, but not limited to, engineers and
          other professional consultants. Tenant will be responsible for the
          repair of any damage that the installation of the Parking Structure
          Sign may cause to the Building or Property. Tenant agrees upon the
          expiration date or sooner termination of this Lease, upon Landlord's
          request, to remove the Parking Structure Sign and to repair and
          restore any damage to the Building and Property at Tenant's expense.
          In addition, Landlord shall have the right to remove the Parking
          Structure Sign at Tenant's sole cost and expense, if, at any time
          during the Lease Term: (1) Tenant sublets more than 35% of the
          Premises (except in connection with a Permitted Transfer), (2) Tenant
          and any Permitted Transferee cease to occupy at least 65% of the
          Premises, or (3) Tenant defaults under any term or condition of the
          Lease and fails to cure such default within any applicable grace
          period.

     C.   For purposes hereof, the "Parking Signage Conditions" shall mean: (1)
          Tenant has not sublet more than 35% of the Premises (except in
          connection with a Permitted Transfer) prior to the date on which
          Tenant receives all necessary approvals and permits to install the
          Parking Structure Sign; (2) Tenant and any Permitted Transferee are in
          actual occupancy of at least 65% of the Premises on the date on which
          Tenant receives all necessary approvals and permits to install the
          Parking Structure Sign; (3) Tenant is not in default under any term or
          condition of the Lease after notice and the expiration of applicable
          grace periods on the date on which Tenant receives all necessary
          approvals and permits to install the Sign; and (4) Tenant obtains all
          necessary permits and approvals to install the Parking Structure Sign.
          Landlord acknowledges that Tenant shall have the right to transfer its
          rights to the Parking Structure Sign in connection with a Permitted
          Transfer or an assignment of Tenant's entire interest in the Lease to
          an assignee approved by Landlord pursuant to the terms and conditions
          of the Lease, provided that such replacement Parking Structure Sign
          shall be subject to the same approval process set forth herein for the
          original Parking Structure Sign.

XI.  ONE RIVERSIDE SIGNAGE.
     ----------------------

     A.   Provided that Landlord is able to obtain all necessary building
          permits and zoning, regulatory and governmental approvals, Tenant
          shall have the right to install one (1) exclusive sign identifying
          Tenant on the facade of One Riverside Center (the "One Riverside
          Center Sign"). The approximate location and size of the One Riverside
          Center Sign is shown on Exhibit L hereto. Tenant's right to install
          the One Riverside Center Sign shall, however, be subject to the
          satisfaction of all of the One Riverside Signage Conditions (defined
          in subsection XI.B. below). The application for the One Riverside
          Center Sign shall be made as part of a joint application for all
          requests for signage at the Building. In the event that Landlord's
          joint application for signage is not approved, Landlord shall work
          with Tenant and any other tenants represented in such application to
          agree upon an alternative signage plan that is reasonably acceptable
          to all parties and to the City of Newton. Landlord shall have the
          right to retain legal counsel and consultants to represent the joint
          interests of Tenant, Landlord and any other tenants who have been
          granted signage rights and Tenant agrees to pay its proportionate
          share of such costs based on the number of signs for which approval is
          being requested. Tenant acknowledges that Landlord cannot guaranty
          that Tenant will receive the necessary permits and approvals to allow
          Tenant to install the One Riverside Center Sign. Landlord, however,
          shall diligently advocate approval of the proposed signage plan for
          the Building. Tenant agrees to use reasonable efforts to complete its
          specifications for the proposed One Riverside Center Sign so as to
          allow a joint signage application to be submitted for approval in
          January, 2000 (or earlier if reasonably possible).

     B.   All costs in connection with the One Riverside Center Sign, including
          any costs for the design, installation, supervision of installation,
          wiring, maintenance, repair and removal of the One Riverside Center
          Sign, will be at Tenant's expense. Tenant shall submit to Landlord
          reasonably detailed drawings of the proposed One Riverside

                                       15
<PAGE>   68

          Center Sign, including without limitation, the size, material, shape
          and lettering for review and approval by Landlord. The One Riverside
          Center Sign shall conform to the standards of design and motif
          established by Landlord for the exterior of the Building and the
          Property on which it is located. Tenant shall reimburse Landlord for
          any costs associated with Landlord's review and supervision as
          hereinbefore provided including, but not limited to, engineers and
          other professional consultants. Tenant will be responsible for the
          repair of any damage that the installation of the One Riverside Center
          Sign may cause to the Building or Property. Tenant agrees upon the
          expiration date or sooner termination of this Lease, upon Landlord's
          request, to remove the One Riverside Center Sign and to repair and
          restore any damage to the Building and Property at Tenant's expense.
          In addition, Landlord shall have the right to remove the One Riverside
          Center Sign at Tenant's sole cost and expense, if, at any time during
          the Lease Term: (1) Tenant sublets more than 35% of the Premises
          (except in connection with a Permitted Transfer), (2) Tenant and any
          Permitted Transferee cease to occupy at least 65% of the Premises, or
          (3) Tenant defaults under any term or condition of the Lease and fails
          to cure such default within any applicable grace period.

     C.   For purposes hereof, the "Riverside Center Signage Conditions" shall
          mean: (1) Tenant has not sublet more than 35% of the Premises (except
          in connection with a Permitted Transfer) prior to the date on which
          Tenant receives all necessary approvals and permits to install the One
          Riverside Center Sign; (2) Tenant and any Permitted Transferee are in
          actual occupancy of at least 65% of the Premises on the date on which
          Tenant receives all necessary approvals and permits to install the One
          Riverside Center Sign; (3) Tenant is not in default under any term or
          condition of the Lease after notice and the expiration of applicable
          grace periods on the date on which Tenant receives all necessary
          approvals and permits to install the Sign; and (4) Tenant obtains all
          necessary permits and approvals to install the One Riverside Center
          Sign. Landlord acknowledges that Tenant shall have the right to
          transfer its rights to the One Riverside Center Sign in connection
          with a Permitted Transfer or an assignment of Tenant's entire interest
          in the Lease to an assignee approved by Landlord pursuant to the terms
          and conditions of the Lease, provided that such replacement One
          Riverside Center Sign shall be subject to the same approval process
          set forth herein for the original One Riverside Center Sign.

XII. THREE RIVERSIDE SIGNAGE.
     ------------------------

     A.   Provided that Tenant and any Permitted Transferee are in actual
          occupancy of not less than fifty percent (50%) of the total rentable
          square footage of Three Riverside Center, Tenant shall have the right
          to install one (1) non- exclusive sign identifying Tenant on the
          facade of Three Riverside Center (the "Three Riverside Center Sign"),
          the size and location of which shall be reasonably designated by
          Landlord. Tenant's right to install the Three Riverside Center Sign
          shall, however, be subject to the satisfaction of all of the Three
          Riverside Signage Conditions (defined in subsection XII.B. below).
          Tenant, at its sole cost and expense, shall obtain all necessary
          building permits and zoning, regulatory and governmental approval in
          connection with the Three Riverside Center Sign. All costs in
          connection with the Three Riverside Center Sign, including any costs
          for the design, installation, supervision of installation, wiring,
          maintenance, repair and removal of the Three Riverside Center Sign,
          will be at Tenant's expense. Tenant shall submit to Landlord
          reasonably detailed drawings of the proposed Three Riverside Center
          Sign, including without limitation, the size, material, shape and
          lettering for review and approval by Landlord. The Three Riverside
          Center Sign shall conform to the standards of design and motif
          established by Landlord for the exterior of the Building and the
          Property on which it is located. Tenant shall reimburse Landlord for
          any costs associated with Landlord's review and supervision as
          hereinbefore provided including, but not limited to, engineers and
          other professional consultants. Tenant will be responsible for the
          repair of any damage that the installation of the Three Riverside
          Center Sign may cause to the Building or Property. Tenant agrees upon
          the expiration date or sooner termination of this Lease, upon
          Landlord's request, to remove the Three Riverside Center Sign and to
          repair and restore any damage to the Building and Property at Tenant's
          expense. In addition, Landlord shall have the right to remove the
          Three Riverside Center Sign at Tenant's sole cost and expense, if, at
          any time during the Lease Term: (1) Tenant assigns this Lease (except
          in connection with a Permitted Transfer), (2) Tenant sublets more than
          33% of the Premises (except in connection with a Permitted Transfer),
          (3) Tenant and any Permitted Transferee ceases to occupy at least 67%
          of the Premises, (4) Tenant and any Permitted Transferee

                                       16
<PAGE>   69

          cease to occupy at least 50% of the total rentable square footage of
          Three Riverside Center, or (5) Tenant defaults under any term or
          condition of the Lease and fails to cure such default within any
          applicable grace period.

     B.   For purposes hereof, the "Riverside Center Signage Conditions" shall
          mean: (1) Tenant has not assigned its interest in this Lease (except
          in connection with a Permitted Transfer) prior to the date on which
          Tenant receives all necessary approvals and permits to install the
          Three Riverside Center Sign; (2) Tenant has not sublet more than 33%
          of the Premises (except in connection with a Permitted Transfer) prior
          to the date on which Tenant receives all necessary approvals and
          permits to install the Three Riverside Center Sign; (3) Tenant and any
          Permitted Transferee are in actual occupancy of at least 67% of the
          Premises on the date on which Tenant receives all necessary approvals
          and permits to install the Three Riverside Center Sign; (4) Tenant is
          not in default under any term or condition of the Lease after notice
          and the expiration of applicable grace periods on the date on which
          Tenant receives all necessary approvals and permits to install the
          Sign; (5) Tenant obtains all necessary permits and approvals to
          install the Three Riverside Center Sign; and (6) Tenant and any
          Permitted Transferee are in occupancy of not less than 50% of the
          total rentable square footage of Three Riverside Center. Tenant
          acknowledges that, with the exception of a Permitted Transfer, under
          no circumstances shall Tenant have the right to transfer, sell or
          assign any of its rights to the Three Riverside Center Sign.

XIII. SUPPLEMENTAL HVAC UNITS AND ANTENNA/DISHES.
      -------------------------------------------

     A.   Tenant shall have the appurtenant right to use space on the roof of
          the Building (the "Roof Space") for the purpose of installing,
          operating and maintaining up to a total of ten (10), in the aggregate,
          supplemental HVAC units (collectively referred to as the "HVAC Unit")
          and/or satellite dishes or antenna (collectively referred to as the
          "Dish/Antenna"). The HVAC Unit and Dish/Antenna are sometimes
          collectively referred to as "Roof Top Units". Tenant shall have the
          right to determine how many of the 10 Roof Top Units are HVAC Units
          and how many of the 10 Roof Top Units are Dish/Antenna. The exact
          location of the roof space to be used by Tenant shall be designated by
          Landlord, provided, however, Landlord shall take into consideration
          the operating efficiency and/or functionality of the Roof Top Units
          when making such designations. Notwithstanding the foregoing, Tenant's
          right to install the Roof Top Units shall be subject to the reasonable
          approval rights of Landlord and Landlord's architect with respect to
          the plans and specifications for the Roof Top Units, including,
          without limitation, the size, height and dimensions of the Roof Top
          Units, the manner in which the Roof Top Units are is attached to the
          roof of Building, the availability of Building condenser water and the
          manner in which Tenant intends to access the Building condenser water,
          if applicable, and the manner in which any cables are run to and from
          the Roof Top Units. Tenant shall be solely responsible for obtaining
          all necessary governmental and regulatory approvals and for the cost
          of installing, operating, maintaining and removing the Roof Top Units.
          At the request of Landlord, Landlord shall be entitled to oversee any
          requests for governmental or regulatory approvals or to cause Tenant's
          request for approvals to be submitted as part of a joint application
          for approval with any other matters for which Landlord is seeking
          approval with respect to the Building. The precise specifications and
          a general description of the Roof Top Units along with all documents
          Landlord reasonably requires to review the installation of the Roof
          Top Units (the "Plans and Specifications") shall be submitted to
          Landlord for Landlord's written approval no later than 60 days prior
          to the date on which Tenant desires to install the Roof Top Units.
          Tenant shall notify Landlord upon completion of the installation of
          each of the Roof Top Units. If Landlord determines that the Roof Top
          Units do not comply with the approved Plans and Specifications, that
          the Building has been damaged during installation of the Roof Top
          Units or that the installation was defective, Landlord shall notify
          Tenant of any noncompliance or detected problems and Tenant shall
          promptly commence and diligently prosecute cure of the defects. If
          Tenant fails to promptly commence and diligently prosecute cure of the
          defects, Landlord shall have the right, but not the obligation, to
          cure the same, and Tenant shall pay to Landlord upon demand the cost
          reasonably incurred by Landlord of correcting any defects and
          repairing any damage to the Building caused by such installation. If
          at any time Landlord, in its sole discretion, deems it necessary,
          Tenant shall provide and install, at Tenant's sole cost and expense,
          appropriate aesthetic screening, reasonably satisfactory to Landlord,
          for the Roof Top Units (the "Aesthetic Screening"). Tenant shall pay
          Landlord for the cost of all utilities consumed in the operation of
          the Roof Top Units.

                                       17
<PAGE>   70

     B.   Landlord agrees that Tenant, upon reasonable prior notice to Landlord,
          shall have access to the Roof Space for the purpose of installing,
          maintaining, repairing, replacing and removing the Roof Top Units and
          the Aesthetic Screening, all of which shall be performed by Tenant or
          Tenant's authorized representatives or contractors, which shall be
          reasonably approved by Landlord, at Tenant's sole cost and risk. It is
          agreed, however, that only authorized engineers, employees or properly
          authorized contractors of Tenant, FCC (hereinafter defined)
          inspectors, or persons under their direct supervision will be
          permitted to have access to the Roof Space. Tenant further agrees to
          exercise firm control over the people requiring access to the Roof
          Space in order to keep to a minimum the number of people having access
          to the Roof Space and the frequency of their visits.

     C.   It is further understood and agreed that the installation,
          maintenance, operation and removal of the Roof Top Units may in no way
          damage the Building or roof thereof, or interfere with the use of the
          Building and roof by Landlord. Tenant agrees to be responsible for any
          damage caused to the roof or any other part of the Building, which may
          be caused by Tenant or any of its agents or representatives.

     D.   Tenant shall be responsible for the installation, operation,
          cleanliness, maintenance and removal of the Roof Top Units and
          appurtenances, all of which shall remain the personal property of
          Tenant, and, notwithstanding anything in Article VIII of the Lease to
          the contrary with respect to Required Removables, shall be removed by
          Tenant at its own expense at the termination of said Lease. Tenant
          shall repair any damage cause by such removal, including the patching
          of any holes to match, as closely as possible, the color surrounding
          the area where the equipment and appurtenances were attached. Such
          maintenance and operation shall be performed in a manner to avoid any
          interference with any other tenants or Landlord. Tenant agrees to
          maintain all of Tenant's equipment placed on or about the Roof Space
          in proper operating condition and maintain same in satisfactory
          condition as to appearance and safety. Tenant agrees that at all times
          during the term of this Lease, it will keep the Roof Space free of all
          trash or waste materials by Tenant. Tenant must provide Landlord with
          prior notice of any such installation, removal or repair and
          coordinate such work with Landlord in order to avoid voiding or
          otherwise adversely effecting any warranties granted to Landlord with
          respect to the roof. If necessary, Tenant, at its sole cost and
          expense, shall retain any contractor having a then existing warranty
          in effect on the roof to perform such work (to the extent that it
          involves the roof), or, at Tenant's option, to perform such work in
          conjunction with Tenant's contractor. In the event Landlord
          contemplates roof repairs that could effect Tenant's Roof Top Units or
          requires access which requires temporary removal or relocation of the
          Roof Top Units, or which may result in an interruption of the Tenant's
          air conditioning service or antenna/satellite dish use, Landlord shall
          formally notify Tenant at least thirty (30) days in advance (except in
          the case of an emergency) prior to the commencement of such
          contemplated work in order to allow Tenant to make other arrangements
          for such services.

     E.   Landlord, at its sole cost and expense, reserves the right to relocate
          the Roof Space with respect to Antenna/Dishes from time to time as
          necessary during the Term. Notwithstanding the foregoing, Tenant, not
          Landlord, shall be responsible for the cost of any relocation that is
          necessitated by Landlord's performance of repairs or improvements to
          the Building, provided that such improvements are not for the benefit
          of any single tenant or occupant of the Building.

     F.   Tenant agrees to install only Antenna/Dishes of types and frequencies
          which will not cause unreasonable interference to Landlord or existing
          tenants of the Building. In the event Tenant's Antenna/Dish causes
          such interference, Landlord shall work together with Tenant and any
          other parties affected by such interference to reach a mutually
          agreeable solution. In the event the parties cannot arrive at a
          mutually agreeable solution in a prompt manner, Landlord shall have
          the right to require Tenant to change the frequency on which it
          transmits and/or receives and take any other steps necessary to
          eliminate the interference. If said interference cannot be eliminated
          within a reasonable period of time, in the judgment of Landlord, then
          Tenant agrees to remove the Dish/Antenna from the Roof Space.

     G.   Tenant shall, at its sole cost and expense, and at its sole risk,
          install, operate and maintain the Dish/Antenna in a good and
          workmanlike manner, and in compliance with all Building, electric,
          communication, and safety codes, ordinances, standards, regulations
          and requirements, now in effect or hereafter promulgated, of the
          Federal

                                       18
<PAGE>   71

          Government, including, without limitation, the Federal Communications
          Commission (the "FCC"), the Federal Aviation Administration ("FAA") or
          any successor agency of either the FCC or FAA having jurisdiction over
          radio or telecommunications, and of the state, city and county in
          which the Building is located. Under this Lease, the Landlord and its
          agents assume no responsibility for the licensing, operation and/or
          maintenance of Tenant's equipment. Tenant has the responsibility of
          carrying out the terms of its FCC license in all respects. The
          Dish/Antenna shall be connected to Landlord's power supply in strict
          compliance with all applicable Building, electrical, fire and safety
          codes. Neither Landlord nor its agents shall be liable to Tenant for
          any stoppages or shortages of electrical power furnished to the
          Dish/Antenna or the Roof Space because of any act, omission or
          requirement of the public utility serving the Building, or the act or
          omission of any other tenant, invitee or licensee or their respective
          agents, employees or contractors, or for any other cause beyond the
          reasonable control of Landlord, and Tenant shall not be entitled to
          any rental abatement for any such stoppage or shortage of electrical
          power. Neither Landlord nor its agents shall have any responsibility
          or liability for the conduct or safety of any of Tenant's
          representatives, repair, maintenance and engineering personnel while
          in or on any part of the Building or the Roof Space.

     H.   Except as provided in the next sentence, Tenant shall not allow any
          provider of telecommunication, video, data or related services
          ("Communication Services") to locate any equipment on the roof of the
          Building or in the Roof Space for any purpose whatsoever, nor may
          Tenant use the Roof Space and/or Dish/Antenna to provide Communication
          Services to an unaffiliated tenant, occupant or licensee of another
          building, or to facilitate the provision of Communication Services on
          behalf of another Communication Services provider to an unaffiliated
          tenant, occupant or licensee of the Building or any other building.
          Notwithstanding the foregoing, Tenant may allow the Roof Space to be
          used by a provider of Communication Services to Tenant, provided that
          such provider enters into a license agreement for such space with
          Landlord upon terms and conditions (including fees) that are
          commercially reasonable for the suburban Boston area.

     I.   Tenant acknowledges that Landlord may at some time establish a
          standard license agreement (the "License Agreement") with respect to
          the use of roof space by tenants of the Building. Tenant, upon request
          of Landlord, shall enter into such License Agreement with Landlord
          provided that such agreement does not materially alter the rights or
          obligations of Tenant hereunder with respect to the Roof Space.

     J.   Tenant specifically acknowledges and agrees that the terms and
          conditions of Article XIV of the Lease (Indemnity and Waiver of
          Claims) shall apply with full force and effect to the Roof Space and
          any other portions of the roof accessed or utilized by Tenant, its
          representatives, agents, employees or contractors.

     K.   If Tenant defaults under any of the terms and conditions of this
          Section or the Lease, and Tenant fails to cure said default within the
          time allowed by Article XIX of the Lease, Landlord shall be permitted
          to exercise all remedies provided under the terms of the Lease,
          including removing the Dish/Antenna, the appurtenances and the
          Aesthetic Screening, if any, and restoring the Building and the Roof
          Space to the condition that existed prior to the installation of the
          Dish/Antenna, the appurtenances and the Aesthetic Screening, if any.
          If Landlord removes the Dish/Antenna, the appurtenances and the
          Aesthetic Screening, if any, as a result of an uncured default, Tenant
          shall be liable for all costs and expenses Landlord incurs in removing
          the Dish/Antenna, the appurtenances and the Aesthetic Screening, if
          any, and repairing any damage to the Building, the roof of the
          Building and the Roof Space caused by the installation, operation or
          maintenance of the Dish/Antenna, the appurtenances, and the Aesthetic
          Screening, if any.

XIV. BACK-UP GENERATOR.
     ------------------

     A.   Tenant shall have the appurtenant right to install a supplemental
          generator (the "Generator") to provide emergency additional electrical
          capacity to the Premises and an above ground fuel tank (the "Tank") to
          provide fuel to such Generator. The Generator and Tank shall be
          located in the southeast corner of Level A in One Riverside Center,
          the exact location of which shall be designated by Landlord (the
          "Generator Space"). Notwithstanding the foregoing, Tenant's right to
          install the Generator and Tank shall be subject to Landlord's
          reasonable approval of the manner in which the Generator and Tank are
          installed, the manner in which any

                                       19
<PAGE>   72

          cables and lines are run to and from the Generator to the Premises and
          the measures that will be taken to eliminate any vibrations or sound
          disturbances from the operation of the Generator. Landlord shall have
          the right to require an acceptable enclosure to hide or disguise the
          existence of the Generator and Tank and to minimize any adverse effect
          that the installation of the Generator and Tank may have on the
          appearance of the Building and Property. Tenant shall be solely
          responsible for obtaining all necessary governmental and regulatory
          approvals and for the cost of installing, operating, maintaining and
          removing the Generator and Tank. Tenant shall also be responsible for
          the cost of all utilities and fuel consumed in the operation of the
          Generator. Notwithstanding anything herein to the contrary, if Tenant
          does not install the Generator and Tank on or before one (1) year
          after the Commencement Date, Tenant's right to install and maintain
          the Generator or Tank, as appropriate, on the Property shall be
          subject to space being available for such purpose.

     B.   Tenant shall be responsible for assuring that the installation,
          maintenance, operation and removal of the Generator and Tank will in
          no way damage the Building or Property. Tenant agrees to be
          responsible for any damage caused to the Building or Property in
          connection with the installation, maintenance, operation or removal of
          the Generator and Tank and, in accordance with the terms of Article
          XIV of the Lease, to indemnify, defend and hold Landlord and any
          Landlord Related Parties harmless from all liabilities, obligations,
          damages, penalties, claims, costs, charges and expenses which may be
          imposed upon, incurred by, or asserted against Landlord or any of the
          Landlord Related Parties in connection with the installation,
          maintenance, operation or removal of the Generator and Tank,
          including, without limitation, any environmental and hazardous
          materials claims.

     C.   Tenant shall be responsible for the installation, operation,
          cleanliness, maintenance and removal of the Generator, Tank and
          appurtenances, all of which shall remain the personal property of
          Tenant, and, notwithstanding anything in Article VIII of the Lease to
          the contrary with respect to Required Removables, shall be removed by
          Tenant at its own expense at the termination of the Lease. Tenant
          shall repair any damage caused by such removal, including the patching
          of any holes to match, as closely as possible, the color surrounding
          the area where the Generator, Tank and appurtenance were attached.
          Such maintenance and operation shall be performed in a manner to avoid
          any unreasonable interference with any other tenants or Landlord.
          Tenant agrees to maintain the Generator and Tank, including without
          limitation, any enclosure installed around the Generator and Tank, in
          good condition and repair. Tenant shall be responsible for performing
          any maintenance and improvements to any enclosure surrounding the
          Generator and Tank so as to keep such enclosure in good condition.

     D.   Tenant, subject to the reasonable rules and regulations enacted by
          Landlord, shall have access to the Generator and Tank and its
          surrounding area for the purpose of installing, repairing, maintaining
          and removing said Generator and Tank.

     E.   Tenant shall only test the Generator before or after normal business
          hours and upon prior notice to Landlord.

XV.  VACATION OR ABANDONMENT. Landlord hereby agrees that the vacation or
     -----------------------
     abandonment of the Premises by Tenant shall not constitute a default by
     Tenant under the Lease so long as Tenant continues to pay Rent as required
     hereunder. Notwithstanding the foregoing, Tenant, within thirty (30) days
     following its vacation or abandonment of 75% or more of the Premises, shall
     notify Landlord of its intentions regarding reoccupancy. If Tenant abandons
     or vacates 75% or more of the Premises, Tenant shall use reasonable efforts
     to sublet or assign the entire vacant portion of the Premises for the
     remainder of the Lease Term to a party (or parties) that will occupy the
     Premises in accordance with the terms and conditions of the Lease. Such
     reasonable efforts shall require Tenant, at a minimum, to list the Premises
     with a qualified real estate brokerage firm at least thirty (30) days prior
     to such vacation or abandonment and to actively commence to market the
     Premises within thirty (30) days after such listing. Tenant agrees to
     provide Landlord a copy of an executed listing agreement between Tenant and
     a qualified real estate brokerage firm. If Tenant fails to use reasonable
     efforts to sublet or assign the Premises or, even if reasonable efforts are
     used, fails to sublet or assign the majority of the vacated or abandoned
     portion of the Premises within six (6) months after the date of such
     abandonment or vacation, Landlord, at any time thereafter, shall have the
     right to market the abandoned or vacated portion of the Premises for lease
     and, upon obtaining a lessee

                                       20
<PAGE>   73

     for the Premises, recapture the Premises and terminate this Lease by notice
     to Tenant. If Landlord terminates this Lease, Tenant, on a monthly basis
     following receipt of an invoice from Landlord, shall pay Landlord an amount
     equal to the difference between the Rent that was payable under this Lease
     through the remainder of the then current Lease Term that was in effect
     immediately prior to termination (without consideration of any unexercised
     renewal options) and the rent actually received by Landlord for the
     remainder of such Lease Term from any third party lessee of the Premises.
     In addition, Tenant, within thirty (30) days after receipt of demand from
     Landlord, shall reimburse Landlord for all of Landlords reasonable Costs of
     Reletting the Premises.

XVI. INTENTIONALLY OMITTED
     ---------------------

XVII. BUILDING RISERS. Tenant shall have the right to use the vertical sleeves
      ---------------
     in One Riverside Center and Two Riverside Center for Tenant's data and
     telecommunication cabling and in connection with the rights granted to
     Tenant with respect to the Roof Space. All such usage shall be in common
     with Landlord and shall not adversely affect Landlord's right to use the
     vertical sleeves for the operation of the Building (including the leasing,
     licensing and granting of roof rights to third parties); provided that
     Landlord shall not lease, license or grant any roof rights to third parties
     to the extent that the same would have an adverse affect on Tenant's
     ability to use the vertical sleeves in connection with the normal operation
     of Tenant's business in the Premises.

     Landlord and Tenant have executed this exhibit as of the day and year first
above written.

WITNESS/ATTEST:                 LANDLORD:

                                EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
                                LIABILITY COMPANY

                                By:  Beacon Property Management Corporation, a
                                     Delaware corporation, its managing member
/s/ Kathleen M. Steidinger
-----------------------------        By:     /s/ Michael A. Steele
                                            -------------------------
Name (print):
              ---------------        Name:   Michael A. Steele
Kathleen M. Steidinger                      -------------------------
-----------------------------
                                     Title:  President
/s/ John C. Schneider                       -------------------------
-----------------------------
Name (print):
              ---------------
John C. Schneider
-----------------------------

WITNESS/ATTEST:                 TENANT:

                                ALLAIRE CORPORATION, A CORPORATION ORGANIZED
/s/ Eric J. Smith               UNDER THE LAWS OF THE STATE OF DELAWARE
-----------------------------   By:     David A. Gerth
                                       ------------------------------
Name (print): Eric J. Smith
              ---------------   Name:   David A. Gerth
/s/ JoAnne Trayers                     ------------------------------
-----------------------------
                                Title:  CFO & VP Finance & Operations
Name (print): JoAnne Trayers           ------------------------------
              ---------------

-----------------------------

                                       21
<PAGE>   74

                                    EXHIBIT F

                                 NOTICE OF LEASE
                                 ---------------

     Notice is hereby given, pursuant to the provisions of Chapter 183, Section
4 of the Massachusetts General Laws, of the following Lease:

Landlord:
---------

EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED LIABILITY COMPANY
Tenant:
-------

ALLAIRE CORPORATION, A CORPORATION ORGANIZED UNDER THE LAWS OF THE STATE OF
DELAWARE

Date of Lease Execution:
------------------------

  November 23, 1999
------------------------------------

Description of Premises:
------------------------

Approximately 270,446 square feet of space on the 1st, 2nd and 3rd floors of the
building commonly known as One Riverside Center and the 1st and 2nd floors of
the building commonly known as Two Riverside Center ("Premises") shown on the
sketch plan attached hereto as Exhibit "A" and located at 275 Grove Street,
Newton, MA (the "Property") more particularly described on Exhibit "B" attached
hereto and made a part hereof.

Commencement Date:
------------------

The later to occur of (1) July 1, 2000; or (2) the date on which the Landlord
Work in the One Riverside Center Premises has been substantially completed, as
such date is determined pursuant to the Lease, or (3) the Landlord delivers full
possession of the Premises in One Riverside Center to Tenant. The Commencement
Date will be confirmed in a subsequent notice executed by Landlord and Tenant
and recorded in the Registry of Deeds.

Original Term:
--------------

A period of ten (10) years beginning on the Commencement Date.

Option to Extend.
-----------------

The Lease may be extended for two (2) successive additional period of five (5)
years each, subject to the terms and conditions of the Lease.

Expansion Option.
-----------------

Tenant, subject to the terms and conditions of the Lease, has expansion rights
with respect to approximately 32,152 rentable square feet on the 3rd floor of
Two Riverside Center.

Right of First Offer.
---------------------

================================================================================
<PAGE>   75
Right of First Offer.
---------------------

Tenant, subject to the terms and conditions of the Lease, has the right of first
offer with respect all space in Two Riverside Center and Three Riverside Center.

Signage.
--------

Tenant has certain rights, exclusive and non-exclusive, regarding signage on the
exterior of the certain buildings and structures located at the Property, all
upon terms and conditions set forth in the Lease.

Miscellaneous.
--------------

The Lease sets forth additional rights, obligations, terms and conditions not
enumerated herein.

To the extent there is an inconsistency between the Lease and the Notice of
Lease, the Lease shall govern.

For Landlord's title, see deed recorded in Middlesex (South) Registry of Deeds
in Book 27596 at Page 171.

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 24
<PAGE>   76

     WITNESS the execution hereof as a sealed instrument as of the 23rd day of
November, 1999.

WITNESS/ATTEST:                 LANDLORD:

                                EOP-RIVERSIDE PROJECT, L.L.C, A DELAWARE LIMITED
                                LIABILITY COMPANY

                                By:  Beacon Property Management Corporation, a
                                     Delaware corporation, its managing member
/s/ Kathleen M. Steidinger
-----------------------------        By:     /s/ Michael A. Steele
                                            -------------------------
Name (print):
              ---------------        Name:   Michael A. Steele
Kathleen M. Steidinger                      -------------------------
-----------------------------
                                     Title:  President
/s/ John C. Schneider                       -------------------------
-----------------------------
Name (print):
              ---------------
John C. Schneider
-----------------------------

WITNESS/ATTEST:                 TENANT:

                                ALLAIRE CORPORATION, A CORPORATION ORGANIZED
/s/ Eric J. Smith               UNDER THE LAWS OF THE STATE OF DELAWARE
-----------------------------   By:     David A. Gerth
                                       ------------------------------
Name (print): Eric J. Smith
              ---------------   Name:   David A. Gerth
/s/ JoAnne Trayers                     ------------------------------
-----------------------------
                                Title:  CFO & VP Finance & Operations
Name (print): JoAnne Trayers           ------------------------------
              ---------------

-----------------------------

================================================================================
<PAGE>   77

                                STATE OF ILLINOIS

  Cook                  , ss                                        November 23,
------------------------
1999
[County]

     Then personally appeared the above-named Michael A. Steele, the President
of Beacon Property Management Corporation, a Delaware corporation, the managing
member of EOP-Riverside Project, L.L.C., a Delaware limited liability company,
known to me to be the person described in and who executed the foregoing
instrument and acknowledged the same to be his free act and deed and that of
said Beacon Property Management Corporation as the managing member of
EOP-Riverside Project, L.L.C., before me,

                                              Kathleen M. Steidinger
                                              ----------------------
                                              Notary Public
                                              My Commission Expires:June 1, 2001

                          COMMONWEALTH OF MASSACHUSETTS

 Middlesex          , ss                                       November 23, 1999
--------------------
[County]

     Then personally appeared the above-named David A. Gerth the CFO of Allaire
Corporation, a Delaware corporation, known to me to be the person described in
and who executed the foregoing instrument and acknowledged the same to be his
free act and deed and that of said Allaire Corporation, before me,

                                              Victoria Reiff
                                              Notary Public
                                              My Commission Expires:2005

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                        Page 2
<PAGE>   78

                                    EXHIBIT G

                         LEGAL DESCRIPTION OF PROPERTY
                         -----------------------------

     A certain parcel of land containing about four hundred eighty-seven
thousand six hundred (487,600) square feet on the northwesterly side of Grove
Street in that part of the City of Newton, County of Middlesex and Commonwealth
of Massachusetts, known as Riverside, bounded and described as follows:

          EASTERLY by Grove Street, six hundred eighteen and twelve hundredths
     (618.12') feet; SOUTHWESTERLY by land of the Boston and Albany Railroad
     Company by a line forty-one and twenty-five hundredths (41.25') feet
     northeasterly from and parallel to the base line of the Newton Highlands
     Branch of the Boston and Albany Railroad filed September 20, 1884, by three
     (3) courses, the first being two hundred forty-seven and seventy-four
     hundredths (247.74') feet; the second being five hundred seventy-four and
     seventy-five hundredths (574.75') feet; and the third being six hundred
     thirty-eight and seventy-one hundredths (638.71') feet; NORTHWESTERLY by
     land now or formerly of Lyman W. Gore and Minnie S. Gore, one hundred ten
     and seventy hundredths (110.70') feet; NORTHEASTERLY by land now or
     formerly of said Lyman W. Gore and Minnie S. Gore and land now or formerly
     of Murdo Mackenzie and Mary Mackenzie, sixty-four and no hundredths
     (64.00') feet; NORTHERLY by land of various owners and by Oakwood Road and
     Williston Road, one thousand fifty-eight and thirty-five hundredths
     (1,058.35') feet; said premises being shown within the lines tinted brown
     upon a plan hereinafter mentioned; together with an easement consisting of
     the right to install, use, maintain, repair and renew a 12 inch cast iron
     sewer pipe under land of the Boston and Albany Railroad Company from the
     above-described land to the City of Newton sewer on the southwesterly side
     of the said Newton Highlands Branch as shown in purple on the said plan;
     also the right to continue in use, maintain, repair and renew a three (3')
     foot stone box culvert under land of the Boston and Albany Railroad Company
     from the above-described land to Runaway Brook as shown in yellow on said
     plan; said sewer and culvert to be installed, used maintained, repaired and
     renewed with such materials and under such general structural conditions
     and subject to such inspection as shall be approved by the District
     Engineer of the Boston and Albany Railroad, or his duly authorized
     representative.

          The above described premises are shown on entitled "BOSTON & ALBANY
     R.R...: RIVERSIDE LAND COVERED BY B. & A. R. R. CO. TO JORDAN MARSH
     COMPANY," dated June 6, 1951, and signed by C. T. Gunsallus, District
     Engineer, which plan is recorded with Middlesex South District Deeds, Book
     7782, Page 62.

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Riverside Center - Base Building Scope Description                        Page 3
<PAGE>   79

                                    EXHIBIT H
                                  BUILDING PLAN

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                        Page 4
<PAGE>   80

                                    EXHIBIT I
                             SAMPLE LETTER OF CREDIT

                                                      Irrevocable Standby
                                                      Letter of Credit
                                                      No. ______________________
                                                      Issuance Date:____________
                                                      Expiration Date:__________
                                                      Applicant:________________

Beneficiary
-----------

[Insert Name of Owner]
-------------------------------
-------------------------------
-------------------------------

Ladies/Gentlemen:

     We hereby establish our Irrevocable Standby Letter of Credit in your favor
for the account of the above referenced Applicant in the amount of
____________________ U.S. Dollars ($____________________) available for payment
at sight by your draft drawn on us when accompanied by the following documents:

1.   An original copy of this Irrevocable Standby Letter of Credit.

2.   Beneficiary's dated statement purportedly signed by one of its officers
     reading: "This draw in the amount of ______________________ U.S. Dollars
     ($____________) under your Irrevocable Standby Letter of Credit No.
     ____________________ represents funds due and owing to us as a result of
     the Applicant's failure to comply with one or more of the terms of that
     certain lease by and between ______________________, as landlord, and
     _____________, as tenant."

     It is a condition of this Irrevocable Standby Letter of Credit that it will
be considered automatically renewed for a one year period upon the expiration
date set forth above and upon each anniversary of such date, unless at least
sixty (60) days prior to such expiration date or applicable anniversary thereof,
we notify you in writing by certified mail, return receipt requested, that we
elect not to so renew this Irrevocable Standby Letter of Credit. A copy of any
such notice shall also be sent to: Equity Office Properties Trust, 2 North
Riverside Plaza, Suite 2200, Chicago, IL 60606, Attention: Vice
President-Corporate Operations. In addition to the foregoing, we understand and
agree that you shall be entitled to draw upon this Irrevocable Standby Letter of
Credit in accordance with 1 and 2 above in the event that we elect not to renew
this Irrevocable Standby Letter of Credit and, in addition, you provide us with
a dated statement proportedly signed by one of Beneficiary's officers stating
that the Applicant has failed to provide you with an acceptable substitute
irrevocable standby letter of credit in accordance with the terms of the above
referenced lease. We further acknowledge and agree that: (a) upon receipt of the
documentation required herein, we will honor your draws against this Irrevocable
Standby Letter of Credit without inquiry into the accuracy of Beneficiary's
signed statement and regardless of whether Applicant disputes the content of
such statement;

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Riverside Center - Base Building Scope Description                        Page 5

<PAGE>   81

(b) this Irrevocable Standby Letter of Credit shall permit partial draws and, in
the event you elect to draw upon less than the full stated amount hereof, the
stated amount of this Irrevocable Standby Letter of Credit shall be
automatically reduced by the amount of such partial draw; and (c) you shall be
entitled to assign your interest in this Irrevocable Standby Letter of Credit
from time to time without our approval and without charge. In the event of an
assignment, we reserve the right to require reasonable evidence of such
assignment as a condition to any draw hereunder.

     This Irrevocable Standby Letter of Credit is subject to the Uniform Customs
and Practice for Documentary Credits (1993 revision) ICC Publication No. 500.

     We hereby engage with you to honor drafts and documents drawn under and in
compliance with the terms of this Irrevocable Standby Letter of Credit.

     All communications to us with respect to this Irrevocable Standby Letter of
Credit must be addressed to our office located at
______________________________________________ to the attention of
__________________________________.

                                                  Very truly yours,

                                                  ----------------------

                                                         [name]
                                                  ----------------------

                                                         [title}
                                                  ----------------------

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                        Page 6
<PAGE>   82

                                    EXHIBIT J
             SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT

RECORDING REQUESTED BY:
-----------------------
AND WHEN RECORDED MAIL TO:
--------------------------

                                                              Loan No.:_________

                         SUBORDINATION, NON-DISTURBANCE
                            AND ATTORNMENT AGREEMENT
                            ------------------------

     This AGREEMENT made as of ____, 19__, among ______, (hereinafter referred
to as "Landlord" or "Borrower"),____________________________ (hereinafter
referred to as "Tenant"), and (hereinafter referred to as "Lender").

                              W I T N E S S E T H :
                              ---------------------

     WHEREAS, Lender has made or has committed to make a loan or loans
(collectively, the "Loan") to Landlord evidenced by a note (the "Note") to be
secured by a mortgage or deed of trust dated on or about the date hereof
(hereinafter referred to as the "Mortgage") and to be recorded among the real
estate records of ___________________________________, constituting a first
priority security title or lien upon the land described in EXHIBIT A attached
hereto and made a part hereof and the improvements thereon, as well as all of
Landlord's right, title, interest, estate and claim now owned or hereafter
acquired in, to or relating to the items described in (i) through (xii) in the
recitals of the Mortgage (collectively, the "Property"); and

     WHEREAS, Landlord and Tenant have entered into a certain lease dated
_____________, ____, which lease provides for the direct payment of rents from
Tenant to Landlord for the use and occupancy of Suite(s) _______ of that
building (the "Building") on the Property located at ___________________________
(the "Premises") by Tenant, as more fully set forth in the lease (hereafter, the
lease and all existing and future amendments and modifications thereto, and
extensions thereof, shall be referred to as the "Lease"); and

     WHEREAS, Lender wishes to obtain from Tenant certain assurances that Tenant
will attorn to the purchaser at a foreclosure sale in the event of a foreclosure
or to the holder of the Note and Mortgage in the event of such holder's exercise
of its rights under the Note and Mortgage or in the event such holder acquires
title to the Property by deed in lieu of foreclosure or otherwise; and

     WHEREAS, Tenant wishes to obtain from Lender certain assurances that so
long as Tenant is not in default of Tenant's obligations to Landlord under the
Lease, that Tenant shall not be disturbed in its peaceful possession of the
Premises as a result of actions taken by Lender pursuant to its rights under the
Mortgage; and

     WHEREAS, Tenant and Lender are both willing to provide such assurances to
each other upon and subject to the terms and conditions of this Agreement; and

     WHEREAS, Landlord has entered into this Agreement to acknowledge its
agreement to all of the terms and conditions set forth herein.

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                        Page 7

<PAGE>   83

     NOW, THEREFORE, in consideration of the above, the mutual promises
hereinafter set forth, and other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties hereto mutually
agree as follows:

     1. SUBORDINATION AND ATTORNMENT. The Lease and all of the rights of Tenant
        ----------------------------
thereunder shall be and are hereby declared to be and at all times hereafter
shall be and remain subordinate in all respects to the Mortgage and to all
renewals, modifications, consolidations, replacements and extensions thereof and
all of the rights of the Lender thereunder and all other documents securing the
Note. Notwithstanding such subordination, Tenant hereby agrees that the Lease
shall not terminate in the event of a foreclosure of the Mortgage, whether
judicial or nonjudicial or any other proceedings brought to enforce the Mortgage
or by deed in lieu of foreclosure and Tenant further agrees to attorn and to
recognize Lender (as mortgagee in possession or otherwise), or the purchaser at
such foreclosure sale, as Tenant's landlord for the balance of the term of the
Lease, in accordance with the terms and provisions thereof, but subject,
nevertheless, to the provisions of this Agreement, which Agreement shall be
controlling in the event of any conflict.

     2. ESTOPPEL. Landlord and Tenant hereby agree that the Lease is valid,
        --------
enforceable and in full force and effect, that as of the date hereof there are
no defaults by Landlord or Tenant, that there are no setoffs or counterclaims by
Tenant to the payment of rent due under the Lease, that all conditions to the
effectiveness or continuing effectiveness of the Lease required to be satisfied
as of the date hereof have been satisfied, that the Lease has not been modified
or amended except as set forth below (If none, state "None"):
__________________________________________________________________________
__________________________________________________________________________
________________________________________________________________________________
and that the Lease is a complete statement of the agreement of Tenant and
Landlord with respect to the Premises.

     3. TENANT'S REPRESENTATIONS AND WARRANTIES. Tenant hereby represents and
        ---------------------------------------
warrants to Lender that is has not subordinated the Lease or any of its rights
thereunder to any lien, security title or security deed other than the Mortgage
and that it will not subordinate the Lease or its rights thereunder to any lien,
security title or security deed without the prior written consent of Lender,
which may be withheld by Lender in its sole, absolute discretion, without regard
to any reasonableness standard.

     4. LENDER'S NOTICE AND CURE RIGHTS; LENDER'S RIGHT TO RENT. Tenant agrees
        -------------------------------------------------------
with Lender that, from and after the date hereof until payment in full of the
indebtedness under the Note, Tenant will not terminate the Lease, discontinue or
abate the rent or exercise any other remedies as a result of a default by
Landlord under the Lease, without first giving the Lender notice and a
reasonable time, at Lender's option but without any obligation to do so, to cure
or to commence to cure such default. In no event shall the period for Lender to
cure or commence to cure be less than thirty (30) days (or any longer cure
period provided Landlord in the Lease), plus such time as may be required for
Lender or its successors and assigns to take possession of the Building or to
institute and complete foreclosure proceedings or otherwise acquire title to
such Building; provided, however, that such additional period for Lender to
obtain possession or to institute and complete foreclosure proceedings shall not
exceed ninety (90) days unless (i) Lender is diligently pursuing foreclosure
proceedings and (ii) the continuation of the Landlord default in question
neither unreasonably interferes with Tenant's use of the Premises nor imposes
any additional obligations on Tenant, in which case such additional period may
extend to up to one hundred eighty (180) days. Notwithstanding the foregoing, in
the event such default by Landlord under the Lease is not susceptible to cure by
the Lender, Tenant may, at its option, exercise all its rights under the Lease
(including, without limitation, the right to terminate the Lease or discontinue
or abate rent) with prior notice to Lender but without affording Lender the
opportunity to cure.

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                        Page 8

<PAGE>   84

Tenant also agrees that, upon receipt of notice from Lender
or its successors and assigns that it/they has/have exercised its/their rights
under the Assignment of Leases and Rents executed by Landlord in favor of Lender
in connection with the Loan, all rent payments thereafter due under the Lease
shall be paid directly to Lender or its successors and assigns and any such
payments to the Lender shall be credited against the rent due under the Lease as
if made to the Landlord.

     5. NON-DISTURBANCE. So long as Tenant is not in default under the Lease
        ---------------
beyond any notice and cure period provided in the Lease, then Lender agrees with
Tenant that in the event the interest of Landlord under the Lease is acquired by
Lender, or Lender acquires title to the Property or comes into possession of
said Property by reason of foreclosure or enforcement of the Mortgage or the
Note, or by a conveyance in lieu thereof, or by any other means, Tenant's
possession of the Premises and Tenant's rights, privileges and obligations under
the Lease shall not be disturbed, diminished or interfered with by Lender or any
party claiming through Lender during the term of the Lease, including any
extensions thereof permitted to Tenant, and the Lease shall continue in full
force and effect and shall not be terminated except in accordance with the terms
of the Lease. In the event Tenant defaults under the Lease or this Agreement
beyond applicable notice and cure periods, the obligations of Lender hereunder
shall, at Lender's election, become null and void and Lender may proceed to
extinguish the Lease and all of Tenant's rights and interests in and to the
Premises through foreclosure of the Mortgage.

     Immediately upon the acquisition by Lender of possession or title to the
Property by reason of foreclosure or enforcement of the Mortgage or the Note, or
by a conveyance in lieu thereof, or as a result of any other means, Tenant
agrees to be bound to Lender under all of the terms, covenants, and conditions
of the Lease for the balance of the term thereof, including any extensions
thereof permitted to Tenant, with the same force and effect as if Lender were
the landlord under the Lease, and Tenant does hereby attorn to Lender as its
landlord, said attornment to be effective and self-operative without the
execution of any other instruments on the part of either party hereto.

     Lender further agrees that if it obtains possession or title to the
Property during the Lease term, Lender shall be bound to Tenant under all of the
terms, covenants, and conditions of the Lease and Tenant shall, from and after
the occurrence of the events set forth above, have the same remedies that Tenant
might have had under the Lease against Landlord; provided; however, that Lender
shall not be:

     a.   liable to Tenant for damages for any act or omissions of Landlord or
          any prior landlord occurring prior to Lender obtaining possession or
          title to the Property; or

     b.   subject to any offsets, claims or defenses which Tenant might have
          against Landlord or against any prior landlord which arise prior to,
          or out of any events that occurred prior to, the date Lender obtains
          possession or title to the Property (except any offset or deduction
          expressly provided for in the Lease which amount is a sum certain
          expressly set forth in the Lease); or

     c.   bound by any rent or additional rent or deposit, rental security or
          any other sums which Tenant may have paid to Landlord or any other
          landlord unless received by Lender; or

     d.   bound by any amendment or modification of the Lease made from and
          after the date of this Agreement without Lender's prior written
          consent; or

     e.   bound to the Tenant subsequent to the date upon which the Lender
          transfers its interest in the Property to any third party; or

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                        Page 9

<PAGE>   85

     f.   obligated or liable to Tenant with respect to the construction and
          completion of any improvements in the Premises for tenant's use,
          enjoyment or occupancy; provided, however, if, after succeeding to
          Landlord's interest under the Lease Lender fails or refuses to
          construct or complete any such improvements which Landlord would have
          been obligated to construct or complete, Tenant shall be entitled to
          exercise any and all remedies provided to Tenant by the Lease for a
          failure by Landlord to construct or complete any such improvements; or

     g.   obligated or liable to Tenant for any moving, relocation or
          refurbishment allowance or any payment or allowance for improvements
          to the Premises of any part thereof; provided, however, if after
          succeeding to Landlord's interest under the Lease Lender fails or
          refuses to pay any such allowance, Tenant shall be entitled to
          exercise any and all remedies provided to Tenant by the Lease for a
          failure by Landlord to pay any such allowance; or

     h.   liable for the payment of any leasing commissions or other expenses
          for which Landlord or any prior landlord incurred the obligation to
          pay; or

     i.   bound or liable to Tenant under any notice given by Tenant to Landlord
          or any prior landlord unless notice is also given simultaneously to
          Lender as required by the terms of this Agreement; or

     j.   personally liable for any obligations of Landlord under the Lease to
          which Lender succeeds, Lender's liability for the performance of such
          obligations being limited at all times to its interest in the
          Property.

     6. OBLIGATIONS OF SUCCEEDING OWNER. Tenant hereby agrees that any entity or
        -------------------------------
person which at any time hereafter becomes the Landlord under the Lease,
including, without limitation, Lender, as a result of Lender's exercise of its
right under the Mortgage, or a purchaser from Lender, shall be liable only for
the performance of the obligations of the Landlord under the Lease which arise
and accrue during the period of such entity's or person's ownership of the
Property.

     7. NOTICES. All notices or other written communications required or
        -------
permitted to be given pursuant to this Agreement shall be in writing, and shall
be deemed to have been properly given (i) upon delivery, if delivered in person
or by facsimile transmission with receipt acknowledged, (ii) one business day
after having been deposited for overnight delivery with any reputable overnight
courier service, or (iii) upon actual receipt (or upon refusal to accept
delivery or upon the date delivery is attempted and cannot be completed because
the party to whom it is sent can no longer be found at the then current notice
address) if sent by registered or certified mail, postage prepaid, addressed as
follows:

if given to Tenant, shall be addressed as follows:

                     Allaire Corporation
                     One Riverside Center
                     Newton, Massachusetts 02458
                     Attention: General Counsel

           with a copy to:

                     Foley, Hoag & Eliot LLP
                     One Post Office Square
                     Boston, Massachusetts 02109

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 10

<PAGE>   86

                     Attention: Robert L. Birnbaum, Esq.

and, if given to Landlord, shall be addressed as follows:

                     Equity Office Properties Trust
                     Two North Riverside Plaza
                     Suite 2200
                     Chicago, Illinois  60606
                     Attention: Associate General Counsel for Property
                                Operations

and, if given to Lender, shall be addressed as follows:

                     ________________________
                     ________________________
                     ________________________
                     ________________________

or addressed as such party may from time to time designate in a writing to the
other parties hereto and delivered in accordance with the provisions of this
Section 7.

     8. MISCELLANEOUS. This Agreement may not be amended or modified in any
        -------------
manner other than by an agreement in writing, signed by the parties hereto or
their respective successors in interest, and this Agreement shall be binding
upon and inure to the benefit of the parties hereto and their respective
successors and assigns. The words "foreclosure" and "foreclosure sale" as used
herein shall be deemed to include the acquisition of Landlord's estate in the
Property by any power of sale contained in the Mortgage, or by voluntary deed,
assignment or other conveyance or transfer in lieu of foreclosure; and the word
"Lender" shall include the Lender herein specifically named, any Co-Lender(s)
designated by Lender, and any of Lender(s)' successors and assigns, including
anyone who shall have succeeded to Landlord's interest in the Property or
acquired possession thereof by, through or under foreclosure of the Mortgage, or
by any other manner of enforcement of the Mortgage, or the Note or other
obligation secured thereby.

     9. CONFLICTS WITH LEASE. This Agreement shall supersede, as between Tenant
        --------------------
and Lender, all of the terms and provisions of the Lease which are inconsistent
with this Agreement, but shall not affect any obligations or liabilities of
Borrower, as landlord, under the Lease or diminish any of the rights or increase
any of the obligations of Tenant under the Lease.

     10. GOVERNING LAW; VENUE. This Agreement shall be construed in accordance
         --------------------
with the laws of the Commonwealth of Massachusetts and any litigation arising
out of this Agreement shall be brought in the courts of the Commonwealth of
Massachusetts or in the courts of the United States for the applicable District
within the Commonwealth of Massachusetts and all parties hereto consent to the
venue of such courts.

     11. EFFECT OF AGREEMENT. Landlord joins in the execution and delivery of
         -------------------
this Agreement for the purpose of evidencing its consent to the terms and
provisions hereof, and as between Landlord and Tenant, nothing herein contained
shall be deemed to alter or modify the Lease. Landlord authorizes and directs
Tenant to comply with any and all notices from Lender which directs Tenant to
make rent payments directly to Lender. As between Lender and Landlord, nothing
contained herein shall be deemed to alter or modify the terms and conditions of
the Note, the Mortgage, or any other document or agreement regarding the
mortgage loan made by Lender to Borrower.

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 11

<PAGE>   87

     12. CONSTRUCTION. All capitalized terms not otherwise defined herein shall
         ------------
have the meanings ascribed to such terms in the Mortgage.

     14. SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon Borrower,
         ----------------------
Tenant and Lender and their respective successors and assigns, and, subject to
any and all restrictions on transfer and assignment set forth in the Lease (as
to Tenant) or the Mortgage (as to Borrower), shall inure to the benefit of
Borrower, Tenant and Lender and their respective successors and assigns.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement under
seal as of the date first above written.

Signed, sealed and delivered             TENANT:
as to Tenant in the presence of:

                                         -------------------------------

----------------------------
Witness

                                         By:____________________________

                                         Name:__________________________

                                         Title:_________________________

----------------------------
Witness

                                         Attest:________________________

                                         Name:__________________________

                                         Title:_________________________

                                         LENDER:

----------------------------
Witness

                                         By:____________________________

                                         Name:__________________________

                                         Title:_________________________

----------------------------
Witness
WITNESS/ATTEST:                          BORROWER:

                                         By:____________________________

                                         Name:__________________________

                                         Title:_________________________

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 12
<PAGE>   88

----------------------------
Witness

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 13
<PAGE>   89

                                    EXHIBIT K
                       LOCATION OF PARKING STRUCTURE SIGN

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 14
<PAGE>   90

                                    EXHIBIT L
                      LOCATION OF ONE RIVERSIDE CENTER SIGN

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 15
<PAGE>   91

                                    EXHIBIT M
                               BASE BUILDING SCOPE

[EQUITY OFFICE LOGO]

BASE BUILDING SCOPE DESCRIPTION

RIVERSIDE CENTER
275 GROVE STREET
NEWTON, MASSACHUSETTS

January 13, 1999
revised April 6, 1999
revised September 21, 1999

--------------------------------------------------------------------------------
Riverside Center - Base Building Scope Description                       Page 16
<PAGE>   92

                                Table of Contents

CODE REVIEW..............................................................3

       Introduction...........................................................3
STRUCTURE................................................................9

    Design Criteria...........................................................9
    Foundations and Footings..................................................9
    Ground Floor Slab Construction...........................................10
    Superstructure...........................................................10
BUILDING ENVELOPE.......................................................10

    Exterior Walls and Windows...............................................10
    Exterior Entrance and Service Doors......................................10
    Loading Dock.............................................................11
    Roofing..................................................................11
    Mechanical Penthouses....................................................11
INTERIOR CONSTRUCTION...................................................11

    Grove Street Entrance Lobby / Atrium.....................................11
    Interior Partitions......................................................12
    Interior Doors...........................................................12
    Elevators................................................................13
    Exit Stairs..............................................................13
    Toilet Rooms.............................................................13
    Equipment and Furnishings................................................13
FINISH SCHEDULE.........................................................13

PLUMBING SYSTEMS........................................................14

    Design Criteria/Code/Standards...........................................14
    Plumbing Fixtures........................................................15
    Domestic Water Distribution..............................................15
    Piping...................................................................16
    Type.....................................................................16
    Joints...................................................................16
    Domestic Water Equipment.................................................16
    Sanitary Waste Systems...................................................16
    Rain Water Drainage Systems..............................................16
HEATING, VENTILATING, AND AIR CONDITIONING (HVAC) SYSTEMS...............17

    Design Criteria/Code/Standards...........................................17
    Fuel Supply Systems......................................................17
    Heat Generation Systems..................................................17
    Cooling Systems..........................................................18
    Air Distribution.........................................................18
    Controls.................................................................18
FIRE PROTECTION SYSTEMS.................................................18

    Design Criteria/Codes/Standards..........................................18
    Fire Protection Sprinkler Systems........................................19
ELECTRICAL SYSTEMS......................................................19

    Building Power Distribution..............................................19
    Building Electrical Design Load..........................................20
    Wiring Methods and Devices...............................................21
    Lighting.................................................................22
    Fire Alarm System........................................................22
    Emergency Power Systems..................................................23
    Telephone and Data Systems...............................................24
    Security Systems.........................................................24
SITEWORK................................................................24

    Site Improvements - Paved Areas..........................................24
SITE PLUMBING UTILITIES.................................................25

    Water Supply and Distribution Systems....................................25
    Sanitary Sewer Systems...................................................25
SITE ELECTRICAL DISTRIBUTION............................................25

    Site Lighting............................................................25

================================================================================
<PAGE>   93

CODE REVIEW

                                  INTRODUCTION

275 Grove Street, Ward 4, Auburndale, Section 43, Block 29, Lot 4 containing
approximately 487,578 square feet of land following special permit/site plan
approval of petition approval 40-97-2 is the rehabilitation of an existing
building. The proposed office structure will be four (4) stories above grade,
and the proposed garage structure will be five (5) stories above grade with two
(2) stories below grade.

The building is segmented into three (3) subbuildings: 1 Riverside Center to the
north, 2 Riverside Center to the southeast, and 3 Riverside Center to the
southwest. Each subbuilding contains a building core consisting of toilet rooms,
mechanical shaft, tenant electrical room, emergency electrical room, elevators,
and two (2) egress stairs.

The corresponding floors of the north and south subbuildings are at different
elevations. In order to resolve the elevational differences a "T" shaped,
split-level atrium was created to separate the north and south subbuildings.
Each subbuilding is entered through the atrium and half of the egress capacity
is exited through the atrium. The atrium is also accessible from the basement
parking garage within 1 Riverside Center via a shuttle elevator.

The office building, parking structure, and below grade parking garage will be
protected throughout by an automatic sprinkler system.

The following is a code analysis summary:

1.   CODE REFERENCE

          The following is a partial list of applicable codes and regulations.
          The general contractor shall comply with all applicable codes,
          ordinances, regulation, requirements of the special permit, and all
          authorities having jurisdiction.

               A.   Commonwealth of Massachusetts State Building Code - 6th
                    Edition

               B.   Commonwealth of Massachusetts Architectural Access Board
                    (521 CMR)

               C.   American Disabilities Act (ADA)

               D.   Massachusetts Elevator Regulations (524 CMR)

               E    Massachusetts Fuel Gas and Plumbing Codes (248 CMR)

               F.   Massachusetts State Electric Code (527 CMR)

               G.   National Electric Code (NEC) Latest Edition

               H.   NFPA 101 (Chapter 14) - 1985 Edition

               I.   NFPA 13 - 1989 Edition

--------------------------------------------------------------------------------
<PAGE>   94

2.   OCCUPANCY TYPE

          Existing occupancy is Use Group S-1, moderate hazard storage. After
          renovation the occupancy will be classified as:

               A.   Business (Use Group B)

               B.   Low Hazard Storage (Public Garage, Group 2), Basement
                    Parking Level and Adjacent Parking Structure

               C.   The atrium will be subject to the requirements of 780 CMR
                    404.0, including fire protection, smoke control, enclosure,
                    fire alarm and egress.

3.   CONSTRUCTION TYPE

          The maximum single floor area is 161,358 square feet. For use Group B
          occupancies this requires:

               A.   Type 1B construction: floor areas and height not limited.

4.   BUILDING TYPE

               A.   Building Height Allowable:   51'-5" (not including skylight)
                    --------------------------
                    Building Height Actual:      51'-5"
                    -----------------------

               B.   Number of Stories Allowable: 4 stories
                    ---------------------------
                    Number of Stories Actual:    4 stories
                    ------------------------

               C.   Total Floor Area Allowable:  497,099 square feet
                    --------------------------
                    Total Floor Area Actual:     495,850 square feet
                    -----------------------

<TABLE>
<CAPTION>
FIRST FLOOR (NORTH) BLDG. 1   68,983 SF         SECOND FLOOR   (NORTH)       BLDG. 1             69,858 SF
<S>                           <C>     <C>          <C>         <C>           <C>    <C>          <C>
                              (SW)    Bldg. 2      29,129 SF                 (SW)   Bldg. 2      29,354 SF
                              (SE)    Bldg. 3      36,122 SF                 (SE)   Bldg. 3      36,590 SF
                                                                             -----------------------------
                              (Atrium)             24,375 SF                 Total              135,802 SF
                              ------------------------------
                              Total               158,609 SF

                 Third Floor  (North) Bldg. 1      69,858 SF   Fourth Floor  (SW)   Bldg. 2      29,210 SF
                              (SW)    Bldg. 2      29,354 SF                 (SE)   Bldg. 3      36,427 SF
                                                                             -----------------------------
                              (SE)    Bldg. 3      36,590 SF                 Total               65,637 SF
                              ------------------------------
                              Total               135,802 SF
</TABLE>

     Note: Area calculations above developed for the Special Permit were based
     upon Schematic Design drawings.

--------------------------------------------------------------------------------
<PAGE>   95

               D.   Open Perimeter

               The building has a fire separation distance of thirty (30) feet
               on all sides, except at the parking garage. When there are two
               buildings on a lot, the fire separation distance is measured to
               an imaginary line between them and the fire separation distance,
               measured perpendicular to the exterior wall of each building, is
               the distance from the exterior wall to the imaginary line. Walls
               of open parking structures containing openings must have a fire
               separation distance greater than ten (10) feet. If the imaginary
               line is placed ten (10) feet one (1) inch from the point closest
               to the office building just inside the west curb line of the
               north-south driveway between them, the fire separation distance
               for the office building will be more than twenty seven (27) feet.
               For a fire separation of greater than twenty five (25) to thirty
               (30) feet, the area of unprotected openings in an exterior wall
               of a building protected throughout by an automatic sprinkler
               system is not limited. (Table 705.3)

               No exterior wall rating is required (Table 705.2).

               E.   100% Sprinklered: Yes
                    -----------------

5.   FIRE RATINGS PROVIDED

          A. Mechanical Shafts           2 hours     (Table 603)
          B. Elevator & Stair Shafts     2 hours     (Table 602)
          C. Exit Access Corridors       0 hours     (Auto. Fire Sup. System
                                                     Section 1011.4)
          D. Structural Columns          2 hours     (Table 602)
          E. Floor Construction          2 hours     (Table 602) Including Beams
          F. Roof Construction           1 1/2 hours (Table 602, less than 15')
          G. Atrium Skylight             0 hours     (Table 602, more than 20')
          H. Elevator Machine Rooms      2 hours     (Elevator Code)
          I. Emergency Generator Room    2 hours     (Fire Regulations)
          J. Electrical Switchgear Rooms 2 hours     (Electrical Code)

          K. Atrium: Combination of 1 hour fire partition and tempered glass
             wall will be protected by an automatic sprinkler system

6.   INTERIOR FINISH REQUIREMENTS

     A.   Minimum Flame Spread Classification: walls and ceilings (Table 803.4)
          ---------------------------------------------------------------------

               Use Group B
               -----------
                    Vertical exits and passageways             I
                    Corridors providing exit access            II
                    Rooms or enclosed spaces          III

--------------------------------------------------------------------------------
<PAGE>   96

     B.   Minimum floor finish classifications (805.3)

               Use Group B
               -----------
                    Vertical exits and passageways             II
                    Corridors providing exit access            II
                    Rooms or enclosed spaces               DOC-FF-1

     C.   Smoke Developed:
          ----------------
                    Smoke developed rating of all interior materials not to
                    exceed 450 (ASTM E84)

7.   EGRESS ELEMENTS

     A.   Occupant load determined in accordance with 780 CMR 1008.00

                    Use Group B:       Design occupant load, see chart below for
                    ------------       typ. floor
                    Use Group S-2:            200 gross square feet per occupant
                    --------------

B.   EGRESS WIDTH PER PERSON, WITH SPRINKLER SYSTEM (780 CMR 1009.2)

                    Stairways:                     0.2 inches
                    ----------
                    Doors, ramps, corridors:       0.15 inches
                    ------------------------

     C.   Minimum number of exits per floor (780 CMR 1010.2)

                    500 occupants or less:              2
                    501 - 1,000 occupants:              3

     D.   Minimum width of passageways, aisleways, aisles and corridors is 44
          inches (780 CMR 1011.3)

     E.   Minimum means of egress stairways shall be not less than 44 inches in
          width (780 CMR 1014.3)

<TABLE>
<CAPTION>
                    AREA                   MAXIMUM         STAIRWAYS
                 DESCRIPTION              OCCUPANTS        PROVIDED
         ===============================================================
          Office Building Typical Floor
<S>                                          <C>               <C>
                  Building 1                 400               4
                  Building 2                 200               2
                  Building 3                 240               2
</TABLE>

--------------------------------------------------------------------------------
<PAGE>   97

<TABLE>
<CAPTION>
         EGRESS CONVERGENCE          MAXIMUM     STAIRWAYS
         (780 cmr 100.94)           OCCUPANTS    PROVIDED
         =======================================================================
<S>                                    <C>           <C>       <C>
         Stairways N1 and N4

         Basement                      345           2         173 persons/stair
         2nd Floor (North)             400           4         100 persons/stair

         TOTAL/STAIR:       273 Persons        Minimum door width =    41 Inches
</TABLE>

<TABLE>
<CAPTION>
         PARKING STRUCTURE      OCCUPANTS   STAIRWAYS   STAIR WIDTH   DOOR WIDTH
         =======================================================================
<S>                               <C>           <C>        <C>           <C>
         Typical Floor            254           2          25.4"         19.05"
</TABLE>

<TABLE>
<CAPTION>
         EGRESS CONVERGENCE
         (780 CMR 100.94)       OCCUPANTS   STAIRWAYS     STAIR         DOOR
                                                          WIDTH         WIDTH
         =======================================================================
<S>                               <C>          <C>
         Stairways G1 and G2

         Basement                 254          2
         2nd Floor                254          2

         TOTAL:      254 Persons          Minimum door width =       51.9 Inches
</TABLE>

E.             Length of Travel Allowable

                   Use Group B:                 250 feet with sprinklers
                   -----------
                   Use Group S-2:               300 feet without sprinklers
                   -------------
                   Use Group S-2:               400 feet with sprinklers
                   -------------

          G.   Stairs Provided

                   Width:                       44 inches (stringer to stringer)
                   ------
                   Risers:                      7 inches maximum
                   -------
                   Treads:                      11 inches minimum
                   -------
                   Rails:                       2'-10" (height above nosing)
                   ------
                                                2'-10" and 1'-7" at H.C. Ramps

                   Guardrails:                  3'-6" AFF
                   -----------

8.   TOILET FIXTURES

          In each room one (1) water closet and one (1) lavatory is accessible
          to persons in wheelchairs as per the Commonwealth of Massachusetts
          Architectural Access Board (521CMR).

--------------------------------------------------------------------------------
<PAGE>   98

          Fixture Counts:
          ---------------

<TABLE>
<CAPTION>
                                             Women                      Men
          -----------------------------------------------------------------------------
          Typical Floor   Population    W.C.        Lav.      W.C.     Urinals     Lav.
          =============================================================================
<S>                           <C>        <C>         <C>        <C>       <C>        <C>
          Bldg. 1A            200        5           4          3         1          2
          Bldg. 1B            200        5           4          3         1          2
          Bldg. 2             200        5           4          3         1          2
          Bldg. 3             240        6           4          3         1          2
</TABLE>

                     Drinking fountains required:             1 per core
                     ----------------------------
                     Service sinks required:                  1 per core
                     -----------------------

9.   FIRE SUPPRESSION

     A.   The building is equipped throughout with an automatic sprinkler
          system.

     B.   Fire extinguishers are placed throughout the building to comply w/
          NFPA10.

     C.   Fire Alarm

THE BUILDING IS EQUIPPED WITH A FULLY ADDRESSABLE AUTOMATIC FIRE DETECTION,
               ALARM, AND COMMUNICATION SYSTEM. THE SYSTEM INCLUDES THE
               FOLLOWING FIRE DETECTION FEATURES: HVAC EQUIPMENT SMOKE
               DETECTORS, SPRINKLER WATERFLOW SWITCHES, AND ELEVATOR LOBBY AND
               MACHINE ROOM SMOKE DETECTORS. THE SYSTEM MAY BE ZONED SEPARATELY
               TO ALLOW FOR DIRECTIONAL FLOW DURING AN ALARM. THE FIRE ALARM
               SYSTEM ALSO INCLUDES VISUAL AND AUDIBLE NOTIFICATION THROUGHOUT.

10.  EXTERIOR ACOUSTICS

     Acoustical calculations performed by the acoustical engineer of record
     indicate the noise produced by transformers, chillers, air conditioners,
     mechanical/ventilation systems, HVAC equipment and similar devices comply
     with the City of Newton noise ordinance and shall not exceed 51 d.b.a.
     during the day and 48 d.b.a. during night as measured at the property line
     or any location on immediately abutting residential properties.

11.  SIGNAGE

     A.   Signage will be installed designating/restricting the parking spaces
          in front of the building for short term guest parking only with
          parking in those spaces restricted from use between 7 a.m. to 9 a.m.

     B.   Signage will be installed restricting the entry of vehicles for
          parking on the roof of the garage from 9 p.m. to 6 a.m.

     C.   Signage will be installed prohibiting deliveries to the loading docks
          from 10 p.m. to 6 a.m., 7 a.m. to 9 a.m. and 4 p.m. to 6 p.m. Signage
          will also direct any truck seeking the use of the loading docks during
          these time periods to leave the site.

--------------------------------------------------------------------------------
<PAGE>   99

     D.   Signage will be installed to control the route of tractor-trailers and
          large single body delivery trucks on the site. Signage will restrict
          the exit of trucks from the site towards Route 128. U.S. Postal,
          Federal Express, and United Parcel Service type vehicles will be
          exempt from this condition.

     E.   Signage will be installed indicating the following: Right turns into
          the site and left turns out of the site shall be permitted at the
          northern driveway. The center driveway shall be used only as an
          entrance. Only right turns out of the southernmost driveway shall be
          permitted.

12.  LIGHTING

     A.   Lighting controls will be employed in the garage lighting system to
          turn off the top level of garage lighting no later than 9 p.m. and
          turn on no earlier than 6 a.m. seven days a week. There are no light
          poles on the roof of the garage. Emergency and security lighting are
          excluded from this provision.

     B.   Lighting in the surface parking areas shall be shut off no later than
          11 p.m., except for security lighting.

     C.   Lighting along the residential side of the property shall be focused
          inward to the site on poles which are no higher than eighteen (18)
          feet. The source of lighting throughout the site shall not be seen
          from abutting properties. Lighting shall not overspill onto abutting
          properties.

     D.   Roadway lighting to and from the garage will be provided by bollards
          with directed light reflectors aimed downward. The sources of lighting
          shall not be visible.

     E.   All lighting in the atrium shall be aimed downward and is designed to
          minimize intrusion into the neighborhood at night.

13.  GENERAL SPECIAL PERMIT PROVISIONS

     A.   The dumpster, trash compactor, trash recycling equipment, trash
          bailer, and all trash removal equipment is located inside the
          building.

     B.   Bicycles will be parked in the basement of the building.

STRUCTURE

DESIGN CRITERIA

The building is designed to support structural and seismic loads in accordance
with the Massachusetts State Building Code, as follows:

     WIND LOADS:                    Zone 3, Exposure B, 21 psf and distributions
                                    in accordance with section 1621.0.

     SEISMIC LOADS:                 V=CsW, where Cs = 1.2AvS/(RT2/3)

     SNOW LOADS:                    30 psf plus drifting as required by code

The building is designed to support the following live loads:

     FIRST FLOOR SLAB ON GRADE:     100 psf

     FLOORS ABOVE GRADE:            80 psf + 20 psf partition allowance

     HANGING LOAD ALLOWANCE:        10 psf total for ceiling, lighting,
                                    mechanical, and electrical equipment.

FOUNDATIONS AND FOOTINGS

     WALL FOUNDATIONS: Cast-in-place concrete walls on continuous strip footings
     around perimeter of the building extending to at least 4'-0" below grade.
     Perimeter insulation provided as required by code.

--------------------------------------------------------------------------------
<PAGE>   100

     COLUMN FOUNDATIONS: Interior columns are supported on cast-in-place
     concrete spread footings. Concrete piers and pilasters at exterior wall are
     supported on spread footings extending to at least 4'-0" below grade.

GROUND FLOOR SLAB CONSTRUCTION

     SLABS ON GRADE: Cast-in-place concrete slabs reinforced with welded wire
     fabric on 4" of compacted granular material over a vapor barrier on a
     compacted base course.

     ELEVATOR PIT: Cast-in-place concrete walls on a mat footing.

SUPERSTRUCTURE

     EXISTING FLOORS LEVELS 'C', 'D','E', AND 'G': Cast-in-place 8" concrete
     slabs with 45 1/2" deep drop panels at columns.

     EXISTING COLUMNS AT LEVELS 'A', 'B', 'C', 'D': Cast-in-place concrete, 20"
     diameter at interior and 16" square at perimeter and building expansion
     joints.

     EXISTING COLUMNS AT LEVELS 'G' AND 'J': Rolled steel, wide flange shapes,
     prime-painted and left exposed.

     NEW COLUMNS AT LEVELS 'E' AND 'H': Rolled steel, wide flange shapes,
     prime-painted and left exposed

     EXISTING ROOF CONSTRUCTION (SOUTH BUILDING): 1 1/2" deep metal roof deck
     supported by open web bar joists (28" deep) and rolled steel girders (18"
     deep).

     NEW ROOF CONSTRUCTION (NORTH BUILDING): 1 1/2" deep, 20 gauge painted, type
     B metal roof deck supported by rolled steel beams and rolled steel girders.

BUILDING ENVELOPE

EXTERIOR WALLS AND WINDOWS

     ARCHITECTURAL PRE-CAST CONCRETE PANELS: The ground floor walls are pre-cast
     concrete panels with an architectural finish. Joints are finished with
     high-performance silicone sealant.

     BRICK VENEER PANELS: Wall surfaces above the ground floor are standard
     modular face brick veneer, supported by cold-formed metal framing. (ASTM C
     216, Grade SW)

     CURTAIN WALL PANELS: Curtain wall panels alternate with brick veneer
     panels. Aluminum curtain wall frames are Kawneer 1600 or equal with a
     high-performance fluoropolymer color 2-coat system (Kynar 500) finish and
     glazed with 1 inch thick insulating glass with low-emissivity coating.

     FIXED WINDOWS: Fixed punch windows are located in brick veneer panels.
     Windows are fabricated from extruded aluminum framing with thermal break
     construction and a high-performance fluoropolymer color 2-coat system
     (Kynar 500) finish and glazed with 1 inch thick insulating glass with
     low-emissivity coating.

     LOUVERS: Louvers provided at mechanical rooms are extruded aluminum with a
     high-performance fluoropolymer color 2-coat system (Kynar 500) finish.

     INTERIOR FINISH: Insulation, vapor barrier, studs, and drywall provided.
     Drywall taped and ready for tenant finishes.

     WINDOW STOOLS: Tenant to provide painted hardwood or equal.

EXTERIOR ENTRANCE AND SERVICE DOORS

The three primary building entrances are identified by a bay of full-height
aluminum curtain wall, glazed with 1-inch thick insulating glass with
low-emissivity coating. Each entrance has a vestibule with thermal break
entrance doors providing thermal isolation from the exterior.

--------------------------------------------------------------------------------
<PAGE>   101

     EGRESS DOORS: Egress stairs discharge to the outside through glazed
     aluminum doors matching the building exterior window system.

     SERVICE DOORS: Extra heavy duty, 16 gauge, insulated seamless flush steel
     doors, in fully welded, 14 gauge galvanized steel frames. Doors and frames
     are finish painted.

LOADING DOCK

Each building has a loading dock, located at the rear of the building, equipped
with dock bumpers, truck restraints, and an overhead door. Yellow markings and
rubber bumpers meeting OSHA requirements are provided.

     BUILDING 1: A scissors-type elevating dock platform 6'-0" x 9'-0"with a
     capacity of 25,000 pounds, per ANSI MH14.1 is provided.

ROOFING

A fully adhered single-ply rubber roof membrane is provided.

     MEMBRANE: .060" thick ethylene propylene diene monomer (EPDM) sheet

     ELASTOMERIC FLASHING AND TUBING: Uncured .060" thick neoprene sheet tubing
     at vertical and horizontal expansion conditions

     ROOF INSULATION: 2-pound density, square-edged extruded polyisocyanurate
     foam insulation board

     MEMBRANE UNDERLAYMENT: "Dens-Deck" fiberglass faced gypsum sheathing

     WALKWAY PROTECTION: shredded EPDM rubber walkway pads

MECHANICAL PENTHOUSES

STAIR BULKHEADS AND ELEVATOR MACHINE ROOMS ARE CLAD WITH PRE-FINISHED METAL
PANELS. ROOFTOP AIR HANDLERS ARE PREFABRICATED, SELF CONTAINED UNITS.

INTERIOR CONSTRUCTION

GROVE STREET ENTRANCE LOBBY / ATRIUM

The main entrance lobby and atrium is a four-story space overlooking a central
water feature, cafe seating, and newsstand. The atrium is enclosed by a full
height curtain wall at each end, and covered by a vaulted skylight.

     FLOOR: Granite agglomerate tile and carpet.

     WALLS: Combination of wood paneling with aluminum framed windows are
     provided at the ground floor. Gypsum wallboard with aluminum framed windows
     are provided at the upper floors.

     CEILINGS: Custom vaulted skylight

     INTERIOR DOORS: Full height glass entrance doors.

--------------------------------------------------------------------------------
<PAGE>   102

INTERIOR PARTITIONS

Interior partitions for the base-building construction are of steel stud and
drywall construction. Fire-rated partitions are provided as required by the
Building Code. Gypsum board exposed to tenant areas has joints taped and filled,
and ready for TENANT FINISHES in the following areas: toilet rooms, janitors
closets, electrical closets, exitway stairs, exitway corridors, elevator shafts
and elevator machine rooms. The public side of the main entrance lobby and
atrium will be FINISHED as part of the base building.

     EXIT STAIR ENCLOSURES: 2-hour rated; 3-5/8" deep (25 gauge) galvanized
     steel studs; two (2) layers of 5/8" gypsum board both sides, or 2-hour
     rated 8" concrete masonry units with one (1) layer of 5/8" gypsum board on
     both sides.

     ELEVATOR SHAFT: 2-hour rated shaft wall, or 2-hour rated 8" concrete
     masonry units with one (1) layer of 5/8" gypsum board on both sides.

     SERVICE SHAFT ENCLOSURES: 2-hour rated shaft wall, or 2-hour rated 8"
     concrete masonry units with one (1) layer of 5/8" gypsum board on both
     sides.

     Non-rated partitions are constructed of 3-5/8" deep, (25 gauge) galvanized
     steel studs with one (1) layer of 5/8" gypsum board both sides.

     COLUMNAR ENCLOSURES: All new and existing FREESTANDING columns are exposed.
     ALL COLUMNS ENGAGED WITH THE EXTERIOR WALL ARE ENCLOSED WITH ONE (1) LAYER
     OF 5/8" GYPSUM BOARD ON STEEL STUDS.

INTERIOR DOORS

     DOORS AND FRAMES: Doors are 1-3/4" solid core wood, 7-ply construction with
     WITH MAHOGANY VENEER. Door frames are 16 gauge pressed metal. Doors and
     frames are primed and painted.

     DOOR HARDWARE: Base building interior doors are provided with heavy duty
     commercial grade, mortised locksets and latchsets with lever handles. All
     Base Building doors are furnished with locks, except at toilet rooms and
     stairs.

--------------------------------------------------------------------------------
<PAGE>   103

ELEVATORS

The following elevators are provided.

<TABLE>
<CAPTION>
                                      Geared          Hydraulic           Total
                                     Traction
              =================================================================
<S>                                     <C>               <C>               <C>
              Building 1                4                 0                 4
              Building 2                2                 0                 2
              Building 3                3                 0                 3
              Atrium                    0                 2                 2
              Parking Structure         2                 0                 2
              -----------------------------------------------------------------
                   Total               11                 2                13

              Cab Capacity          3,500 lbs           varies              -
              Cab Speed              150 fpm            varies              -
</TABLE>

     HOIST WAY DOORS AND FRAMES: Polished stainless steel at ground floor
     lobbies. Factory baked enamel at all other lobbies.

     CAB FINISHES: Carpet floor, millwork, interior panels, and ceiling.

EXIT STAIRS

Exit stairs consist of concrete-filled steel pan treads and platforms, steel
railings and handrails, constructed to NAAMM (National Association of
Architectural Metal Manufactures) "Commercial" grade.

     *    Exposed steel is primed and painted with semi-gloss paint.

     *    Exposed concrete treads and landings are sealed with clear sealer.

     *    Walls are painted with latex eggshell finish paint.

TOILET ROOMS

Fully accessible toilet rooms are provided on each floor.

     FLOOR: 2"x 2" ceramic mosaic tile.

     WALLS: 4"x 4" glazed ceramic tile on the "wet" wall, full height stalls,
     and to underside of counter at lavatory wall. Multi-color fleck paint, and
     4x4 ceramic tile base are provided at the remaining walls. A mirror is
     located above the lavatory counter.

     CEILING: Painted 5/8" gypsum wallboard

     TOILET PARTITIONS: Overhead hung, steel panels with powder coat finish.

     LAVATORY COUNTER: Polished granite agglomerate

     PLUMBING FIXTURES: White vitreous china

     TOILET ACCESSORIES: Stainless steel, durable accessories.

EQUIPMENT AND FURNISHINGS

     FIRE EXTINGUISHERS: Portable multi-purpose dry type, 20A-60BC extinguishers
     in cabinets ARE PROVIDED WITHIN COMMON AREAS, at appropriate locations
     conforming to NFPA 13. Fully recessed cabinet; painted steel trim and door
     with DSA glass pane.

     WINDOW BLINDS: Vertical slat PVC blinds are provided at all exterior AND
     ATRIUM windows WITHIN TENANT AREAS to maintain a uniform appearance from
     the exterior.

FINISH SCHEDULE

--------------------------------------------------------------------------------
<PAGE>   104

<TABLE>
<CAPTION>
  ----------------------------------------------------------------------------------------------------------------------------------
           ROOM                     FLOOR            BASE                        WALLS                               CEILING
  ----------------------------------------------------------------------------------------------------------------------------------
<S>                           <C>                   <C>        <C>                                         <C>
  Entrance Lobby / Atrium           Tile,            Tile       Curtain wall, wood panels and wallboard          Custom Skylight
                                    carpet                               with alum. Windows
  ----------------------------------------------------------------------------------------------------------------------------------
       Toilet Rooms           Porcelain Mosaic       Tile       4"x 4" glazed wall tile on "wet" walls;    Painted gypsum wall board
                                 Tile, 2"X 2"                      latex paint at other walls; mirror
                                                                         above lavatory counter
  ----------------------------------------------------------------------------------------------------------------------------------
         Stairways             Sealed Concrete      Vinyl                     Latex Paint                     Gypsum wall board (@
                                                                                                               underside of roof)
  ----------------------------------------------------------------------------------------------------------------------------------
    Electrical Closets         Sealed Concrete      Vinyl               Solid color latex paint                 Exposed Structure
  ----------------------------------------------------------------------------------------------------------------------------------
   Elevator Machine Room       Sealed Concrete      Vinyl               Solid color latex paint                 Exposed Structure
  ----------------------------------------------------------------------------------------------------------------------------------
       Tenant Spaces          Unsealed Concrete      None      Refer to interior partitions description         Exposed Structure
                                                               for areas provided with gypsum wall board
  ----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

PLUMBING SYSTEMS

DESIGN CRITERIA/CODE/STANDARDS

Plumbing fixture quantity based upon designed occupancy of each floor.

--------------------------------------------------------------------------------
<PAGE>   105

The following codes, standards and references shall be utilized as applicable:

     Massachusetts Uniform State Plumbing Code 248 CMR 2.00.
     Massachusetts Fuel Gas Code 248 CMR 3.00 through 8.00.
     Commonwealth of Massachusetts State Building Code, Sixth (6th) Edition.
     National Electric Code (NEC)
     Local Ordinances, Regulations of the City of Newton.
     Insurance Underwriter.
     American Society of Heating, Refrigerating and Air Conditioning Engineers
     (ASHRAE).
     Massachusetts Water Resources Authority (MWRA).

PLUMBING FIXTURES

     TOILET ROOM FIXTURES: Fixtures are commercial grade, white vitreous china,
     wall hung, and/or countertop mounted, low consumption type. Wall hung
     fixtures are provided with floor mounted commercial grade fixture carriers.

     WATER CLOSETS AND URINALS: Flush valve operated with chrome-plated, brass
     construction, low consumption flush valves.

     LAVATORY FAUCETS: Automatic metering and tempering, self-closing faucets of
     chrome-plated brass construction.

     ELECTRIC WATER COOLERS: Bi-level, wall mounted

     JANITORS' SINK: Molded fiberglass

DOMESTIC WATER DISTRIBUTION

Domestic cold water is metered at the service entry point and distributed to
toilet room fixtures, janitor's closets, and electric water coolers, and "wet"
columns..

     WATER HEATING: Electric water heaters are provided on the lowest floor of
     each building in the janitor's closet to serve the toilet rooms. Tenants
     requiring hot water must provide water heaters supplied by cold water from
     the "wet" columns.

     EXTERIOR WALL HYDRANTS: A complete system of exterior wall hydrants will be
     provided and spaced along the building exterior at 100-foot intervals. Each
     wall hydrant will be served by a 3/4" cold water line with shutoff valve.

     BACKFLOW PREVENTERS: Installed at each connection to base building
     mechanical equipment mounted in accordance with DEP requirements, complete
     with air gap fitting and drip piping.

     PIPING INSULATION: Cold water, hot water, hot water recirculation and
     horizontal storm drainage piping is insulated with pre-formed fiberglass
     pipe insulation with all-service jacket and molded elbow fittings.

--------------------------------------------------------------------------------
<PAGE>   106

     "WET" COLUMNS: Cold water risers are provided remote from the toilet room
     cores as follows:

          Building 1A:           2
          Building 1B:           2
          Building 2:            2
          Building 3:            2

PIPING                       TYPE                          JOINTS

Cold Water                   Type "L" Hard Copper          95/5 (Lead Free)

Hot Water                    Type "L" Hard Copper          95/5 (Lead Free)

Hot Water Recirculation      Type "L" Hard Copper          95/5 (Lead Free)

Underground Water Service    Cement Lined Ductile Iron,    Mechanical
                             Class 52

DOMESTIC WATER EQUIPMENT

WATER HEATERS: Electric storage type with hot water recirculation including,
element, controls, vacuum, temperature, and pressure relief valves piped to a
floor drain. Heaters are located in the closest janitor's closet.

SANITARY WASTE SYSTEMS

Sanitary drainage systems collects liquid wastes from plumbing fixtures and
floor drains. The systems are trapped and vented. Soil and vent stacks are
provided at "wet" columns.

Floor drains are installed in all toilet rooms containing two or more flushing
fixtures, all mechanical rooms, penthouses, and other areas containing
mechanical equipment.

Drainage systems includes a complete system of gravity vents to maintain trap
seals, with extensions to the atmosphere above the roof.

RAIN WATER DRAINAGE SYSTEMS

Rain water is collected at each roof into roof drains with internal vertical
storm conductors to underground collection network.

Roof drains are located at low points of sloped roof areas. Inside the building,
drain piping is sloped at 1/8" per foot. Piping is 12" in diameter or smaller.

--------------------------------------------------------------------------------
<PAGE>   107

HEATING, VENTILATING, AND AIR CONDITIONING (HVAC) SYSTEMS

DESIGN CRITERIA/CODE/STANDARDS

     OUTDOOR DESIGN CONDITIONS:

          Summer:              88(0) F.D.B./74(0) F.W.B.

          Winter:              0(0) F

     INDOOR DESIGN CONDITIONS:

          Summer:              78(0) F.D.B./50% RH

          Winter:              72(0) F.D.B.

     OUTSIDE AIR VENTILATION: Outside air will be introduced as required by
     ASHRAE 62-1989, "Ventilation for Acceptable Indoor Air Quality."

The HVAC loads will be based on the following assumptions:

          Lighting Load (including task lighting)            2.0 watts/ RSF
          Computers & Miscellaneous Cooling Loads            4.0 watts/ RSF
          Occupancy                                          1 PERSON/175 RSF

FUEL SUPPLY SYSTEMS

The heating fuel source is electricity.

The cooling fuel source is electricity.

Domestic hot water is provided by electric hot water heaters.

HEAT GENERATION SYSTEMS

After unoccupied periods the building will be heated to occupied temperatures by
using the fan powered terminal units in a morning warm-up mode. During the
warm-up, the rooftop units will operate at full speed and the return dampers
shall be open.

During occupied hours the heat loss through the exterior walls will be offset by
fan powered variable air volume (VAV) boxes equipped with electric heating
coils. The loss through the roof will be offset by electric unit heaters located
in the ceiling plenum. During unoccupied hours the equipment setpoints will
automatically be reduced.

Electric plenum heaters are provided above the parking garage ceiling beneath
Building 1.

--------------------------------------------------------------------------------
<PAGE>   108

COOLING SYSTEMS

Ventilation is available during occupied hours from the eight (8) rooftop units
(RTUs). These packaged units have electrically driven evaporative mechanical
cooling. The units provide variable air volume (VAV) with variable frequency
drives. Each unit is equipped with smoke detectors and smoke dampers in
accordance with the building code.

<TABLE>
<CAPTION>
                          Units      Tonnage per Unit        Total Tonnage
                          -----      ----------------        -------------
<S>                         <C>             <C>              <C>
         Building 1         4               150                   600
         Building 2         2               225                   450
         Building 3         2               225                   450
                                                             -------------
                                                                1,500
</TABLE>

Each RTU is mounted on roof curbs specifically designed to dampen vibration and
sound from entering the building.

AIR DISTRIBUTION

The HVAC system was designed assuming the following tenant system design:

Vertical air distribution is via medium pressure (3 inch) galvanized sheet metal
risers from the rooftop units. Horizontal branch STUBS on each floor will extend
20'-0" from THE vertical risers. The Tenant will provide all ductwork downstream
from the horizontal STUBS. The Landlord will provide VAV boxes for fit-up of
tenant areas per the following criteria. The cost of installation, thermostats,
electrical wiring, and controls, to be funded within the TIW Allowance.

     *    The perimeter zones TO be designed for one (1) fan powered VAV box per
          1,200 RSF.
     *    The perimeter zones TO be 12 feet deep (as measured from the exterior
          wall).

All interior spaces will be designed for one (1) VAV box per 2,000 RSF. The
ceiling cavity will be used as a return air plenum.

The lobby is provided with fan powered VAV boxes connected by low-pressure
distribution ductwork to linear diffusers.

Toilet rooms and janitor closets are exhausted by low pressure ductwork
connected to roof mounted exhaust fans.

CONTROLS

A computer driven, direct digital control (DDC) energy management system is
provided. Independent temperature controls modulate each VAV box to maintain
setpoint. The system supports the following operational features:

     *    Scheduling of occupied hours.
     *    Economizer cycle for the RTU to use outside air for cooling when
          possible.
     *    RTU on/off alarm.
     *    Toilet exhaust fan on/off.

FIRE PROTECTION SYSTEMS

DESIGN CRITERIA/CODES/STANDARDS

The building is designed to be full-sprinklered throughout using a wet-pipe
sprinkler system. A dry pipe system for unheated parking garage areas will be
provided.

Primary risers and horizontal branches are provided. Distribution piping and
pendant heads are provided in common areas, toilet rooms, electric closets,
janitor's closets, stairs, and the mechanical penthouse. The system, including
future tenant work, is designed to meet the following codes and performance
criteria.

     *    Automatic sprinkler system is classified as ordinary hazard group 1
          occupancy and is designed with a minimum design density of .15 GPM per
          square foot over the hydraulically most remote 1,500 SF. Maximum
          protection area per sprinkler head shall be 130 SF. Hose allowance
          shall be 250 GPM. A minimum of 10 psi cushion

--------------------------------------------------------------------------------
<PAGE>   109

          between required pressure and available pressure shall be maintained.

TENANT AREAS: General distribution piping and upturned heads are provided.
Tenant is responsible for any additional piping, swing arms, and pendant heads
required to accommodate tenant fit-out.

THE FOLLOWING CODES, STANDARDS, AND REFERENCES SHALL BE UTILIZED AS APPLICABLE:

          Commonwealth of Massachusetts State Building Code (CMR 780) Sixth
          Edition (6th Edition).
          National Electric Code (NEC).
          Local Ordinances, Regulations of the Town of Newton.
          National Fire Protection Association (NFPA).
          Insurance Underwriter.

FIRE PROTECTION SPRINKLER SYSTEMS

The service pipes are equipped with double check valve assemblies. Risers are
equipped with wet-pipe sprinkler alarm valves with trim, electric bells, water
motor gongs, excess pressure pumps, main shut-off OS & Y gate valves with
supervisory/tamper switches, and fire department Siamese connections.

ELECTRICAL SYSTEMS

BUILDING POWER DISTRIBUTION

     MAIN ELECTRICAL SWITCHBOARDS: Power distribution assemblies rated at
     277/480 volt, 3 phase 4 wire with main protective devices, utility metering
     compartments, digital metering units to monitor voltage, current, and
     demand kW, and distribution sections with feeder protective devices.

--------------------------------------------------------------------------------
<PAGE>   110

     Main switchboards current ratings are as follows:

<TABLE>
<S>                                  <C>
          Building 1                 4,000 amp
          Building 2                 3,000 amp
          Building 3                 3,000 amp
          Parking Structure          1,200 amp
</TABLE>

     Main protective devices are an insulated case circuit breaker 100% rated,
     with solid state tripping capable of adjusting long time, short time, and
     ground fault protection characteristics.

     Feeder protective devices are group mounted, molded case circuit breakers.

     Main switchboards short circuit rating are 65,000 amp RMS.

BUILDING ELECTRICAL DESIGN LOAD

<TABLE>
<CAPTION>
     Building 1
     ----------
<S>                                                    <C>
          Site lighting                                   10 kW
          Base bldg. cooling, 600 tons A/C               900 kW
          Base bldg. heating                             500 kW
          Common area lighting and power                  95 kW
          Elevators                                      210 kW

          Tenant lighting at 2.0 W/SF                    420 kW
          Tenant receptacles at 4.0 W/SF                 840 kW
          Tenant heating at 6.0 W/SF                   1,260 kW
                                                       --------

     Total Building 1 Load                             4,235 KW

     Building 2
     ----------

          Site lighting                                   15 kW
          Base bldg. cooling, 450 tons A/C               625 kW
          Base bldg. heating                             475 kW
          Common area lighting and power                  50 kW
          Elevators                                       85 kW

          Tenant lighting at 2.0 W/SF                    250 kW
          Tenant receptacles at 4.0 W/SF                 500 kW
          Tenant heating at 6.0 W/SF                     750 kW
                                                       --------

     Total Building 2 Load                             2,750 KW
</TABLE>

--------------------------------------------------------------------------------
<PAGE>   111

<TABLE>
<CAPTION>
     Building 3
     ----------
<S>                                                    <C>
          Base bldg. cooling, 450 tons A/C               625 kW
          Base bldg. heating                             425 kW
          Common area lighting and power                  50 kW
          Elevators                                      125 kW

          Tenant lighting at 2.0 W/SF                    300 kW
          Tenant receptacles at 4.0 W/SF                 600 kW
          Tenant heating at 6.0 W/SF                     900 kW
                                                       --------
     Total Building 3 Load                             3,025 KW

PARKING STRUCTURE ELECTRICAL DESIGN LOAD

          Lighting and power                             115 kW
          Ventilation                                     30 kW
          Heating                                         70 kW
          Elevators                                      150 kW
          Other                                           28 kW
                                                       --------
     Total Parking Structure Load                        393 KW
</TABLE>

     BASE BUILDING POWER DISTRIBUTION: The HVAC rooftop units are power fed
     directly from the main switchboard.

     Two (2) sets of "house" 277/480-volt power, lighting, and 120/208-volt
     receptacle panelboards are installed in the first floor and top floor
     electrical closets.

     TENANT POWER DISTRIBUTION: One tenant electrical distribution closet is
     provided per building core on each floor. One (1) vertical power
     distribution bus duct riser is provided at each building core. Lighting
     panels, dry-type transformers, and 120/208-volt receptacle panels shall be
     furnished and installed by the Tenant.

     The tenant shall install a check meter at each bus duct riser connection to
     monitor energy use.

     PANELBOARDS: Dead front, circuit breaker type manufactured in accordance
     with UL standards. Circuit breakers are molded-case type with an
     interrupting rating determined on the basis of short-circuit study
     calculations.

WIRING METHODS AND DEVICES

     CONDUCTORS: Copper with 75 degrees C insulation, rated for 600 volts, types
     THHN, THWN, or XHHW. Minimum size wire for power and lighting circuits
     shall be No. 12 AWG. Metal-clad MC type cable is allowed for installation
     above the ceiling from the junction boxes to the wall outlets/switches.
     Wiring between junction boxes and branch circuit home runs shall be in EMT.

     CONDUITS: Steel conduit and electric metal tubing (EMT) at a minimum size
     of 1/2 inch. Flexible metal conduit of short lengths (maximum 24 inches)
     shall be provided at all motors and equipment subject to vibration or
     movement.

     DEVICES: Duplex receptacles shall be 20 ampere, 120 volt grounding type,
     specifications grade, UL listed, equal to Hubbell 5352 or 5362. Toggle
     switches shall be 20 ampere, 120/277 volt, specification grade, UL listed.

     GROUNDING: All exposed, noncurrent carrying metallic parts of electrical
     equipment, the raceway system, and the neutral conductor of the wiring
     system shall be grounded in accordance with the Massachusetts Electrical
     Code.

     Separate copper equipment grounding conductor with green outer jacket shall
     be installed with all feeder and branch circuits.

     MATERIALS: All materials shall be UL listed.

--------------------------------------------------------------------------------
<PAGE>   112

LIGHTING

     INTERIOR LIGHTING: The building lobby, exit ways, stairs, mechanical
     penthouse, janitors closets, and electrical closets are illuminated by
     energy-efficient fluorescent fixtures with T8 type lamps and electronic
     ballasts. All recessed down lights are provided with compact fluorescent
     lamps.

     ILLUMINATION LEVELS:

          Main Entrance Lobby                       20-25 FC
          Mechanical and Utility Rooms                 20 FC
          Exit Stairs                                  15 FC

     LAMPS: Energy efficient fluorescent T8 type with 3,500 K color.

     BALLASTS: Electronic type, 277-volt, sound rating Class A, with input
     harmonic distortion of 20% or less.

     EMERGENCY/EGRESS LIGHTING: The building lobby, stairs, and toilet rooms are
     illuminated by fluorescent light fixtures connected to normal/emergency
     standby generator power system. Emergency lighting and exit signs in tenant
     areas are to be provided by the Tenant, and connected to base building
     normal/emergency standby generator system..

     EXTERIOR LIGHTING: Building wall lighting is installed at exit doors and as
     required to illuminate pedestrian walks adjacent to the building.

FIRE ALARM SYSTEM

     BASE BUILDING SYSTEM: Non-coded, analog addressable type, Class A
     supervised, manual and automatic fire alarm system. Fire alarm devices in
     the tenant areas shall be provided by the Tenant and shall be compatible
     with the base building fire alarm control panel and wiring.

     FIRE ALARM PANEL (FACP) SPARE CAPACITY: The FACP shall accommodate all
     initiating circuits, indicating circuits and devices shown on the base
     building drawings plus future tenant area devices.

     The fire alarm control panels have alarm and annunciation capability in
     case of activation of any manual fire alarm station or automatic activation
     of any system smoke detector, heat detector, duct type smoke detector, or
     sprinkler system water flow switch. The panels are sized to include alarm
     zones as required. The respective alarm lamp zone in alarm will light at
     the fire alarm control annunciator, installed recessed in the wall adjacent
     to the main entrance. The fire alarm control panels are tied into the
     municipal fire alarm system via an interior multi-zone master box that
     shall annunciate each individual building. Manual stations and
     audible/visual alarms are provided in accordance with NFPA and ADA
     requirements.

     Audible/visual alarms are the horn-strobe combination type, with horns
     being the vibrating continuous type.

     SMOKE DETECTORS: System smoke detectors are of the photoelectric type
     operated on the light scattering principle. Smoke detectors are provided in
     all electrical/telephone rooms, elevator machine room, elevator lobbies,
     elevator shaft, and atrium.

     Elevator lobbies, shaft, and machine room smoke detection initiates an
     elevator recall sequence.

     Duct type smoke detectors are provided in supply and/or return ducts of the
     air-handling systems as required by NFPA-90A.

     In the event of a power interruption, the system automatically transfers to
     an integral emergency standby battery source.

     The fire alarm master box is located in the main electrical room of South
     Building (2B), and registers an alarm signal at the City of Newton Fire
     Department.

--------------------------------------------------------------------------------
<PAGE>   113

     MANUAL PULL STATIONS: Dual-action addressable type, with key reset.

EMERGENCY POWER SYSTEMS

     A 400 kW/500kVA diesel fired emergency generator is located beneath
     Building 1 which will provide standby emergency power to support the
     following loads within Buildings 1, 2, 3, and the Parking Structure:

     *    Code required egress lighting in the atrium, common elevator lobbies,
          common corridors, mechanical and utility rooms, loading docks, the
          Parking Garage within Building 1, and the Parking Structure.

     *    Panel boards with spare circuit breakers are provided at each core
          electrical closet on each floor to accommodate egress lighting within
          tenant areas.

     *    Atrium smoke exhaust/evacuation fan system

--------------------------------------------------------------------------------
<PAGE>   114

     *    Base building fire alarm system. Terminal cabinets are provided at
          each electrical closet on each floor to accommodate fire alarm devices
          within the tenant areas.

     *    Elevators A1 and A2 in the atrium. Auto recall only for all other
          elevators.

     There is no excess capacity to support any tenant loads other than those
     described above.

TELEPHONE AND DATA SYSTEMS

     BUILDING SERVICE: Underground six (6) 4" conduits encased in concrete and
     manholes are provided from the Bell Atlantic riser poles at Grove Street to
     serve the telephone/data system in all three sub-buildings. Each building
     is served by four (4) 4" conduits installed from the main telephone room in
     basement level of Building 1 to the first floor telephone closet of each
     building core.

     Sufficient capacity exists for additional service providers beyond Bell
     Atlantic.

     TENANT FACILITIES: Telephone/data systems including conduit, cables, jacks,
     and hardware shall be furnished and installed by the Tenant.

SECURITY SYSTEMS

     A base building security system is provided supporting the following
     functions:

     *    Card readers and intercoms at all major building entries
     *    Surveillance cameras at all major building entries and loading docks
     *    Card readers at all ground floor elevator lobbies
     *    Contacts at all exterior doors

     Tenant may provide supplemental security systems as required.

SITEWORK

SITE IMPROVEMENTS - PAVED AREAS

     ROADS: Paved with 4" thick asphalt and edged with concrete or granite
     curbs.

     PARKING AREAS: Paved with 4" thick asphalt and edged with pre-cast concrete
     or granite curbs.

     PEDESTRIAN WALKS: Brick pavers or poured concrete with a broom swept
     finish.

     LANDSCAPING AND PLANTING: New trees and shrubs are hardy native species.
     Planting areas adjacent to the building are provided with a built-in
     irrigation system. Existing vegetation has been retained to the greatest
     extent possible.

--------------------------------------------------------------------------------
<PAGE>   115

SITE PLUMBING UTILITIES

WATER SUPPLY AND DISTRIBUTION SYSTEMS

     WATER MAIN: One (1) 8" diameter Class 52 ductile pipe loop connecting to
     one (1) existing 8" main at Grove Street.

     VALVES: City of Newton standard gate valve.

     FIRE PROTECTION SYSTEM: Four (4) 8" diameter feeds to the building and one
     (1) 8" diameter feed to the parking structure.

SANITARY SEWER SYSTEMS

THREE (3) GRAVITY SEWER CONNECTIONS RUN FROM THE MAIN BUILDING TO THE EXISTING
               SANITARY CONNECTION ON THE UTILITY EASEMENT TO THE SOUTH OF THE
               BUILDING. THE INTERIOR FLOOR DRAINS FOR THE GARAGE STRUCTURE PASS
               THROUGH AN OIL/WATER SEPARATOR AND ARE PUMPED OUT TO A GRAVITY
               SYSTEM CONNECTION IN THE UTILITY EASEMENT AREA TO THE SOUTH OF
               THE BUILDING. THE INTERIOR FLOOR DRAINS FROM THE GARAGE IN THE
               BUILDING ARE DISCHARGED BY GRAVITY THROUGH AN OIL/WATER SEPARATOR
               TO THE SEWER IN GROVE STREET.

SITE ELECTRICAL DISTRIBUTION

     Electrical power service is routed subgrade from the Boston Edison 13.8 kV
     overhead primary line, located at Grove Street.

     A duct bank of four (4) PVC concrete-encased conduits for the underground
     primary feeder and utility manholes are furnished and installed in
     compliance with the Boston Edison standards.

     A total of four (4) pad-mounted transformers, one for each sub-building and
     the parking structure are sized, furnished, and installed by Boston Edison
     Co.

     Utility metering for the sub-buildings and the parking structure will be
     installed in accordance with BECo standards on the secondary 277/480-volt
     side of the pad-mounted transformers.

     The building and parking structure power service will be at the secondary
     voltage 277/480 volt, 3 phase from exterior mounted transformers, located
     as indicated on the electrical site plan. Secondary service feeders of
     copper conductors will be installed underground in the concrete encased, 4"
     PVC conduits, from each pad-mounted transformer to associated main
     electrical switchboard, located in the main Electrical Rooms of the
     building and parking garage.

SITE LIGHTING

     Site lighting is provided in the form of building-mounted fixtures
     illuminating the pedestrian sidewalks adjacent to the building,
     freestanding fixtures on poles illuminating the roadway and parking areas,
     and landscape lighting.

     MINIMUM ILLUMINATION LEVEL: 0.5 FC

--------------------------------------------------------------------------------
<PAGE>   116

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------------------------------
BUILDING COMPONENTS                                                                                    PROVIDED BY
                                                                                                -------------------------
SYSTEM DESCRIPTION                                                                               LANDLORD         TENANT
-------------------------------------------------------------------------------------------------------------------------
<S>                                                                                                 <C>              <C>
BUILDING SHELL

     EXTERIOR WALLS AND WINDOWS
           Architectural Pre-cast Concrete Wall Panels                                              x
           Aluminum Windows                                                                         x
           Curtain Wall                                                                             x
           Louvers & Grills                                                                         x
           Installation of interior gypsum board                                                    x
           Taping and sanding of interior gypsum board                                              x
           Interior window stools                                                                                    x

     ENTRANCES
           Curtain Wall                                                                             x
           Entrance Doors                                                                           x

     EXTERIOR EXIT AND SERVICE DOORS
           Exit Doors                                                                               x
           Service Doors                                                                            x

     LOADING DOCK
           Truck Levelers                                                                           x
           Dock Bumpers                                                                             x
           Overhead Doors                                                                           x
           Trash Compactor                                                                          x

     ROOFING
           Roofing Membrane                                                                         x
           Mechanical Penthouse                                                                     x
           Structural reinforcing for supplemental HVAC units                                                        x
           Elevator Machine Room Penthouse                                                          x
           Stair Penthouse                                                                          x

INTERIORS

     MAIN ENTRANCE LOBBIES
           Flooring                                                                                 x
           Wall finishes                                                                            x
           Ceiling                                                                                  x
           Interior Doors                                                                           x

     INTERIOR PARTITIONS
          Taping and sanding of gypsum board exposed to tenant                                      x
          Painting of gypsum board exposed to tenant areas                                                          x
          Partition face exposed to public areas                                                    x
          Toilet rooms                                                                              x
          Janitors closets                                                                          x
          Electrical and telephone closets                                                          x
          Exitway stairs                                                                            x
</TABLE>

--------------------------------------------------------------------------------
<PAGE>   117

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------------------------------
BUILDING COMPONENTS                                                                                    PROVIDED BY
                                                                                                -------------------------
SYSTEM DESCRIPTION                                                                               LANDLORD         TENANT
-------------------------------------------------------------------------------------------------------------------------
<S>                                                                                                 <C>              <C>

          Elevator shafts and elevator machine rooms                                               x
          Mechanical shafts (Base Building)                                                        x

     INTERIOR DOORS AND HARDWARE
          Public area doors                                                                        x
          Toilet rooms, janitor's closets, electrical and telephone                                x

     ELEVATORS AND CABS
          Passenger Elevators                                                                      x
          Service Elevators                                                                        x

     EXIT STAIRS
          Walls, flooring                                                                          x

     TOILET ROOMS
          Walls, flooring, ceilings, toilet partitions                                             x
          Lavatory counter, plumbing fixtures, toilet accessories                                  x

     EQUIPMENT AND FURNISHINGS
          Fire Extinguishers                                                                       x
          Window Blinds at exterior windows                                                        x

PLUMBING

     PLUMBING FIXTURES
          Water Closets                                                                            x
          Urinals                                                                                  x
          Lavatories                                                                               x
          Electric Water Coolers (one per core)                                                    x
          Janitor's Sink                                                                           x
          Roof Drains                                                                              x
          Wall Hydrants                                                                            x

     DOMESTIC WATER DISTRIBUTION FROM WET COLUMN TO TENANT SPACE
          Water Meter                                                                              x
          Riser at "wet" columns                                                                   x
          Electric water heaters for toilet rooms                                                  x
          Electric water heaters for tenant use                                                                     x

     SANITARY WASTE SYSTEMS
          Riser at "wet" columns                                                                   x
          Toilet room floor drains                                                                 x

     NATURAL GAS SYSTEM
          No service is provided to the site

     COOLING SYSTEMS - BASE BUILDING
          Toilet and janitor room exhaust                                                          x

     COOLING SYSTEMS - TENANT AREAS
          Perimeter zone fan powered VAV box per 1,200 sf                                          x
-------------------------------------------------------------------------------------------------------------------------
BUILDING COMPONENTS                                                                                    PROVIDED BY
                                                                                                -------------------------
SYSTEM DESCRIPTION                                                                               LANDLORD         TENANT
-------------------------------------------------------------------------------------------------------------------------

          Perimeter zone Ductwork FROM CORE TO VAV boxes                                                            x
          Perimeter zone Diffusers and grilles                                                                      x
          Interior zone fan powered VAV box per 2,000 sf                                           x
          Interior zone Ductwork FROM CORE TO VAV boxes                                                             x
          Interior zone Diffusers and grilles                                                                       x
          Diffusers and Grilles in tenant spaces                                                                    x

     CONTROLS & POWER SUPPLY
          Public space controls & POWER                                                            x
          Tenant space VAV box controls & POWER                                                                     x

FIRE PROTECTION SYSTEMS

     SPRINKLER SYSTEM
</TABLE>

--------------------------------------------------------------------------------
<PAGE>   118

<TABLE>
<S>                                                                                                 <C>              <C>
          Primary Loops                                                                            x
          Distribution piping and heads at common areas, toilet                                    x
                  rooms, electric closets, janitors' closets, egress
                  stairs
          GENERAL DISTRIBUTION and UPTURNED heads in tenant areas                                  x
          MODIFICATION OF PIPING, SWING ARMS, AND PENDENT HEADS                                                     x
                  WITHIN TENANT AREAS TO ACCOMODATE FIT-OUT

ELECTRICAL SYSTEMS

     ELECTRICAL SERVICE
          Pad mounted transformers                                                                 x
          Utility metering                                                                         x
          Main electrical switchboards                                                             x

     POWER DISTRIBUTION
          Electrical distribution closets (one per core)                                           x
          Bus duct riser in each electrical closet                                                 x
          Service from bus duct including electronic check meters for                                               x
                  tenant areas
          Panel boards to serve tenant areas                                                                        x
          CHECK METERS                                                                                              X
          Step-down, dry-type transformers to serve tenant areas                                                    x
          Base building life safety standby emergency generator,                                   x
                  transfer switch(es), fuel piping and controls
          Tenant standby emergency generator, transfer switch(es),                                                  x
                  fuel piping and controls
          Emergency lighting panel boards for base building and                                    x
                  tenant areas

     FIRE ALARM SYSTEM
          DEVICES WITHIN base building areas                                                       x
          Devices within tenant areas                                                                               x
</TABLE>

--------------------------------------------------------------------------------
<PAGE>   119

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------------------------------
BUILDING COMPONENTS                                                                                    PROVIDED BY
                                                                                                -------------------------
SYSTEM DESCRIPTION                                                                               LANDLORD         TENANT
-------------------------------------------------------------------------------------------------------------------------
<S>                                                                                                <C>              <C>
     LIGHTING (GENERAL AND EMERGENCY)
          Base building areas including exit ways, stairs, mechanical                              x
                  penthouse, janitors closet, electrical closet and
                  toilet room
          Tenant area lighting                                                                                      x

     TELEPHONE AND DATA SYSTEMS
          Distribution closets and sleeves through floors (one per                                 x
                  core)
</TABLE>

--------------------------------------------------------------------------------
<PAGE>   120

                                    EXHIBIT N
                         SAMPLE CLEANING SPECIFICATIONS

A.   General Cleaning (Monday through Friday)

     1.   All stone, ceramic, tile marble, terrazzo and other unwaxed flooring
          to be swept nightly, using approved dust-down preparation.

     2.   All wood, linoleum, vinyl and similar types of floors to b swept or
          dry mopped nightly,using dust-down preparation; all carpeting and rugs
          in the main traffic areas (corridors, reception areas, etc.) to be
          vacuumed nightly and all other carpeted to be vacuumed at least once
          each week.

     3.   Wax all public areas monthly.

     4.   Hand dust all furniture, files and fixtures nightly.

     5.   Empty all waste and recycling receptacles nightly and remove waste
          paper and waste materials, including folding paper boxes and cartons,
          to a designated area.

     6.   Empty and clean all ashtrays and screen all sand urns nightly.

     7.   Wash and clean all water fountains and coolers nightly.

     8.   Hand dust all door and other ventilating louvers within reach, as
          necessary, but not less often than monthly.

     9.   Dust all telephones as necessary.

     10.  Keep lockers and janitor sink rooms in a neat, orderly condition at
          all times.

     11.  Wipe clean all bright metal work as necessary.

     12.  Check all stairwells throughout entire building nightly and keep in
          clean condition.

     13.  Metal doors and trim of all public elevator cars to be properly
          maintained and kept clean.

B.   Common Area Lavatories

     1.   Sweep and wash all lavatory floors nightly, using proper non-scented
          disinfects.

     2.   Clean all mirrors, powder shelves, bright work and enameled surfaces
          in all lavatories nightly. Scour, wash and disinfect all basins, bowls
          and urinals using non-scented disinfectants.

     3.   Police lavatories during the day with matron or porter to pick up
          waste and replenish materials.

     4.   Wash all toilet seats nightly.

     5.   Fill toilet tissue holders nightly.

     6.   Empty paper towel receptacles nightly.

     7.   Empty sanitary disposal receptacles nightly.

     8.   Thoroughly clean all wall tile and stall surfaces as necessary.

C.   High Dusting

     Do all high dusting (not reached in nightly cleaning) quarterly which
     includes the following:

     1.   Dust all pictures, frames, charts graphs, similar wall hangings.

--------------------------------------------------------------------------------
<PAGE>   121

     2.   Dust exposed pipes, ventilation and air conditioning louvers, ducts
          and high moldings.

D.   Window Cleaning

     1.   All exterior windows (except for any retail/commercial areas) from the
          second floor and above will be cleaned twice per year , inside and
          outside except when cleaning is rendered impracticable by inclement
          weather.

     2.   Entrance door and elevators lobby glass to be cleaned daily and kept
          in a clean condition at all times during the day.

     3.   Wipe down all metal window frames as necessary but not less often than
          monthly.

E.   Building Lobbies

     1.   Floors to be swept and washed or vacuumed nightly, and machine
          scrubbed according to Building Standard frequency.

     2.   Carpeting in passenger elevator cabs to be vacuum cleaned nightly.

     3.   Lobby walls to be dusted as often as necessary, but not less than
          weekly.

     4.   Screen and clean sand urns nightly.

     5.   Clean all painted metal work in a manner appropriate to original
          finish.

F.   Porter

     Necessary number of day porters under supervision will be assigned for the
     following services:

     1.   Service all public and building operating space throughout the
          Building.

     2.   Keep elevator cars clean and neat during the day.

     3.   Maintain lobbies clean and, during wet weather, mop dry to the extent
          practicable.

     4.   Dust and rub all elevator doors, frames, telephones booths and
          directories daily.

     5.   Sweep sidewalks, ramps, etc. daily.

     6.   Clean roofs and setbacks as often as necessary.

     7.   Maintain fire hose and equipment clean.

     8.   Lay and remove lobby runners as necessary.

     9.   Replenish toilet tissue, towels and other supplies in lavatories.

     10.  Maintain fan rooms, motor rooms and air conditioning rooms in clean
          condition.

     11.  Check stairways and keep same neat and clean during the day.

     12.  Clean exterior columns, exterior signs and metal work, standpipe and
          sprinkler system, walkways and stairs as necessary.

--------------------------------------------------------------------------------
<PAGE>   122

                                    EXHIBIT O
                                  ENTRY SIGNAGE

--------------------------------------------------------------------------------
<PAGE>   123

                                    EXHIBIT P
                              FIRST EXPANSION SPACE

--------------------------------------------------------------------------------<PAGE>   1
                                                                   Exhibit 10.24

                        THIRD LOAN MODIFICATION AGREEMENT

         This Third Loan Modification Agreement is entered into as of November
30, 1999, by and between ALLAIRE CORPORATION, a Delaware corporation with its
principal place of business at One Alewife Center, Cambridge, Massachusetts
02140 ("Borrower") and SILICON VALLEY BANK, a California-chartered bank
("Bank"), with its principal place of business at 3003 Tasman Drive, Santa
Clara, CA 95054 and with a loan production office located at Wellesley Office
Park, 40 William Street, Suite 350, Wellesley, MA 02481, doing business under
the name "Silicon Valley East".

1.       DESCRIPTION OF EXISTING INDEBTEDNESS. Among other indebtedness which
may be owing by Borrower to Bank, Borrower is indebted to Bank pursuant to a
loan arrangement dated as of March 26, 1998, evidenced by, among other
documents, a certain Loan and Security Agreement dated as of March 26, 1998, as
amended by certain Loan Modification Agreements dated as of August 6, 1998 and
December 9, 1998 (as amended, the "Loan Agreement"). The Loan Agreement
established in favor of the Borrower a revolving line of credit in the maximum
principal amount of Two Million Dollars ($2,000,000.00) (the "Committed
Revolving Line"). Capitalized terms used but not otherwise defined herein shall
have the same meaning as in the Loan Agreement.

Hereinafter, all indebtedness owing by Borrower to Bank shall be referred to as
the "Indebtedness".

2.       DESCRIPTION OF COLLATERAL. Repayment of the Indebtedness is secured by
the Collateral as described in the Loan Agreement (together with any other
collateral security granted to Bank, the "Security Documents").

Hereinafter, the Security Documents, together with all other documents
evidencing or securing the Indebtedness shall be referred to as the "Existing
Loan Documents".

3.       DESCRIPTION OF CHANGE IN TERMS.

         1.       MODIFICATION(S) TO LOAN AGREEMENT.

                  1.       The Loan Agreement shall be amended by deleting the
                           following definition appearing in Section 1.1
                           thereof:

                                     ""Committed Revolving Line" means a credit
                                     extension of up to Two Million Dollars
                                     ($2,000,000.00)."

                           and inserting in lieu thereof the following:

                                     ""Committed Revolving Line" means a credit
                                     extension of up to Twelve Million Five
                                     Hundred Thousand Dollars ($12,500,000.00),
                                     less the face amount of outstanding Letters
                                     of Credit issued pursuant to Section 2.1.2
                                     hereof."

                  2.       The Loan Agreement shall be amended by inserting
                           immediately after the definition of "ERISA" appearing
                           in Section 1.1 thereof the following definitions:

                                     ""Exchange Contract" has the meaning set
                                     forth in Section 2.1.3.

                                     "Foreign Exchange Reserve" has the meaning
                                     set forth in Section 2.1.3."

<PAGE>   2

                  3.       The Loan Agreement shall be amended by deleting the
                           following definition appearing in Section 1.1
                           thereof:

                                     ""Maturity Date" means the earlier of (i)
                                     March 26, 1999 or (ii) the Equity Event."

                           and inserting in lieu thereof the following:

                                     ""Maturity Date" means November 30, 2000."

                  4.       The Loan Agreement shall be amended by deleting the
                           following text appearing as the first sentence of
                           Section 2.1.1(a) thereof:

                                    "Subject to and upon the terms and
                                    conditions of this Agreement, Bank agrees to
                                    make Advances to Borrower in an aggregate
                                    outstanding amount not to exceed (i) the
                                    Committed Revolving Line or the Borrowing
                                    Base, whichever is less, minus (ii) the face
                                    amount of all outstanding Letters of Credit
                                    (including drawn but unreimbursed Letters of
                                    Credit)."

                           and inserting in lieu thereof the following:

                                    "Subject to and upon the terms and
                                    conditions of this Agreement, Bank agrees to
                                    make Advances to Borrower in an aggregate
                                    outstanding amount not to exceed (i) the
                                    Committed Revolving Line or the Borrowing
                                    Base, whichever is less, minus (ii) the
                                    Foreign Exchange Reserve."

                  5.       The Loan Agreement shall be amended by deleting the
                           following text appearing as paragraph (a) in Section
                           2.1.2 thereof entitled "Letters of Credit":

                                    "Subject to the terms and conditions of this
                                    Agreement, Bank agrees to issue or cause to
                                    be issued Letters of Credit for the account
                                    of Borrower in an aggregate outstanding face
                                    amount not to exceed (i) the lesser of the
                                    Committed Revolving Line or the Borrowing
                                    Base, minus (ii) the then outstanding
                                    principal balance of the Advances; PROVIDED
                                    that the face amount of outstanding Letters
                                    of Credit (including drawn but unreimbursed
                                    Letters of Credit and any Letter of Credit
                                    Reserve) shall not in any case exceed Eight
                                    Hundred Thousand Dollars ($800,000.00). Each
                                    Letter of Credit shall have an expiry date
                                    no later the Maturity Date. All Letters of
                                    Credit shall be, in form and substance,
                                    acceptable to Bank in its sole discretion
                                    and shall be subject to the terms and
                                    conditions of Bank's form of standard
                                    Application and Letter of Credit Agreement."

                           and inserting in lieu thereof the following:

                                    "Subject to the terms and conditions of this
                                    Agreement, Bank agrees to issue or cause to
                                    be issued Letters of Credit for the account
                                    of Borrower provided that the aggregate
                                    outstanding face amount of such Letters of
                                    Credit shall not exceed (i) the Committed
                                    Revolving Line, minus (ii) the then
                                    outstanding principal balance of the
                                    Advances, Foreign Exchange Reserve, and all
                                    other Obligations hereunder (exclusive of
                                    undrawn Letters of Credit). Each Letter of

                                       2
<PAGE>   3

                                    Credit shall have an expiry date no later
                                    than two hundred seventy (270) days after
                                    the Maturity Date provided that Borrower's
                                    Letter of Credit reimbursement obligation
                                    shall be secured by cash on terms acceptable
                                    to Bank at any time after the Maturity Date
                                    if the term of this Agreement is not
                                    extended by Bank. All Letters of Credit
                                    shall be, in form and substance, acceptable
                                    to Bank in its sole discretion and shall be
                                    subject to the terms and conditions of
                                    Bank's form of standard Application and
                                    Letter of Credit Agreement."

                  6.       The Loan Agreement shall be amended by inserting
                           immediately after Section 2.1.2 thereof the following
                           new section entitled "Foreign Exchange Contracts;
                           Foreign Exchange Settlements":

                                     "2.1.3 FOREIGN EXCHANGE CONTRACT; FOREIGN
                                     EXCHANGE SETTLEMENTS.

                                    (a) Subject to the terms of this Agreement,
                                    Borrower may enter into foreign exchange
                                    contracts with the Bank (the "Exchange
                                    Contracts") not to exceed an aggregate
                                    amount of Twelve Million Five Hundred
                                    Thousand Dollars ($12,500,000.00) (the
                                    "Contract Limit"), pursuant to which Bank
                                    shall sell to or purchase from Borrower
                                    foreign currency on a spot or future basis.
                                    Borrower shall not request any Exchange
                                    Contracts at any time it is out of
                                    compliance with any of the provisions of
                                    this Agreement. All Exchange Contracts must
                                    provide for delivery of settlement on or
                                    before the Maturity Date. The amount
                                    available under the Committed Revolving Line
                                    at any time shall be reduced by the
                                    following amounts (the "Foreign Exchange
                                    Reserve") on any given day (the
                                    "Determination Date"): (i) on all
                                    outstanding Exchange Contracts on which
                                    delivery is to be effected or settlement
                                    allowed more than two business days after
                                    the Determination Date, 10% of the gross
                                    amount of the Exchange Contracts; plus (ii)
                                    on all outstanding Exchange Contracts on
                                    which delivery is to be effected or
                                    settlement allowed within two business days
                                    after the Determination Date, 100% of the
                                    gross amount of the Exchange Contracts.

                                    (b) Bank may, in its discretion, terminate
                                    the Exchange Contracts at any time (a) that
                                    an Event of Default occurs or (b) that there
                                    is no sufficient availability under the
                                    Committed Revolving Line and Borrower does
                                    not have available funds in its bank account
                                    to satisfy the Foreign Exchange Reserve. If
                                    Bank terminates the Exchange Contracts, and
                                    without limitation of any applicable
                                    indemnities, Borrower agrees to reimburse
                                    Bank for any and all fees, costs and
                                    expenses relating thereto or arising in
                                    connection therewith.

                                    (c) Borrower shall not permit the total
                                    gross amount of all Exchange Contracts on
                                    which delivery is to be effected and
                                    settlement allowed in any two business day
                                    period to be more than $300,000.00 (the
                                    "Settlement Limit") nor shall Borrower
                                    permit the total gross amount of all
                                    Exchange Contracts to which Borrower is a
                                    party, outstanding at any one time, to
                                    exceed the Contract Limit. Notwithstanding
                                    the above, however, the amount which may be
                                    settled in any two (2) business day period
                                    may be increased above the

                                       3
<PAGE>   4

                                    Settlement Limit up to, but in no event to
                                    exceed, the amount of the Contract Limit
                                    under either of the following circumstances:

                                            (i) if there is sufficient
                                            availability under the Committed
                                            Revolving Line in the amount of the
                                            Foreign Exchange Reserve as of each
                                            Determination Date, provided that
                                            Bank in advance shall reserve the
                                            full amount of the Foreign Exchange
                                            Reserve against the Committed
                                            Revolving Line; or

                                            (ii) if there is insufficient
                                            availability under the Committed
                                            Revolving Line, as to settlements
                                            within any two (2) business day
                                            period, provided that Bank, in its
                                            sole discretion, may: (A) verify
                                            good funds overseas prior to
                                            crediting Borrower's deposit account
                                            with Bank (in the case of Borrower's
                                            sale of foreign currency); or (B)
                                            debit Borrower's deposit account
                                            with Bank prior to delivering
                                            foreign currency overseas (in the
                                            case of Borrower's purchase of
                                            foreign currency).

                                    (d) In the case of Borrower's purchase of
                                    foreign currency, Borrower in advance shall
                                    instruct Bank upon settlement either to
                                    treat the settlement amount as an advance
                                    under the Committed Revolving Line, or to
                                    debit Borrower's account for the amount
                                    settled.

                                    (e) Borrower shall execute all standard form
                                    applications and agreements of Bank in
                                    connection with the Exchange Contracts and,
                                    without limiting any of the terms of such
                                    applications and agreements, Borrower will
                                    pay all standard fees and charges of Bank in
                                    connection with the Exchange Contracts.

                                    (f) Without limiting any of the other terms
                                    of this Agreement or any such standard form
                                    applications and agreement of Bank, Borrower
                                    agrees to indemnify Bank and hold it
                                    harmless, from and against any and all
                                    claims, debts, liabilities, demands,
                                    obligations, actions, costs and expenses
                                    (including, without limitation, reasonable
                                    attorneys' fees and any costs arising out of
                                    the failure of the Borrower to fulfill its
                                    obligations on a timely basis) which the
                                    Bank incurs arising out of or in any way
                                    relating to any of the Exchange Contracts or
                                    any transactions contemplated thereby
                                    (collectively, the "Foreign Exchange
                                    Costs"), provided, however, in no event
                                    shall the Borrower be responsible for
                                    Foreign Exchange Costs to the extent (i)
                                    caused by the Bank's gross negligence or
                                    willful misconduct, or (ii) attributable to
                                    Exchange Contracts entered into by the Bank
                                    for the benefit of other parties."

                  7.       The Loan Agreement shall be amended by deleting the
                           following text appearing as Section 2.2 thereof
                           entitled "Overadvances":

                                    "2.2 OVERADVANCES. If, at any time or for
                                    any reason, the amount of Obligations owed
                                    by Borrower to Bank pursuant to Section
                                    2.1.1 or 2.1.2 of this Agreement is greater
                                    than the lesser of (i) the

                                       4

<PAGE>   5

                                     Committed Revolving Line or (ii) the
                                     Borrowing Base, Borrower shall immediately
                                     pay to Bank, in cash, the amount of such
                                     excess."

                           and inserting in lieu thereof the following:

                                     "2.2 OVERADVANCES. If, at any time or for
                                     any reason, the amount of Obligations owed
                                     by Borrower to Bank pursuant to Section
                                     2.1.1 and 2.1.3 of this Agreement is
                                     greater than: (a) the lesser of (i) the
                                     Committed Revolving Line or (ii) the
                                     Borrowing Base, minus (b) the Foreign
                                     Exchange Reserve, Borrower shall
                                     immediately pay to Bank, in cash, the
                                     amount of such excess."

                  8.       The Loan Agreement shall be amended by deleting the
                           following text appearing as Section 2.3(a) thereof
                           entitled "Interest Rate":

                                     "(a) INTEREST RATE. Except as set forth in
                                     Section 2.3(b), any Advances shall bear
                                     interest, on the average daily balance
                                     thereof, at a per annum rate equal to One
                                     percentage point (1.00%) above the Prime
                                     Rate."

                           and inserting in lieu thereof the following:

                                     "(a) INTEREST RATE. Except as set forth in
                                     Section 2.3(b), any Advances shall bear
                                     interest, effective as of November 30,
                                     1999, on the average daily balance thereof,
                                     at a per annum rate equal to the Prime
                                     Rate."

                  9.       The Loan Agreement shall be amended by deleting
                           Section 6.3 in its entirety and inserting in lieu
                           thereof the following:

                                    "6.3 FINANCIAL STATEMENTS, REPORTS,
                                    CERTIFICATES. Borrower shall deliver to
                                    Bank: (a) as soon as available, but in any
                                    event within forty-five (45) days after the
                                    end of each quarter, a company prepared
                                    consolidated balance sheet and income
                                    statement covering Borrower's consolidated
                                    operations during such period, in a form and
                                    certified by an officer of Borrower
                                    reasonably acceptable to Bank; (b) as soon
                                    as available, but in any event within one
                                    hundred twenty (120) days after the end of
                                    Borrower's fiscal year, audited consolidated
                                    financial statements of Borrower prepared in
                                    accordance with GAAP, consistently applied,
                                    together with an unqualified opinion on such
                                    financial statements of an independent
                                    certified public accounting firm reasonably
                                    acceptable to Bank; (c) promptly upon
                                    receipt of notice thereof, a report of any
                                    legal actions pending or threatened against
                                    Borrower or any Subsidiary that could result
                                    in damages or costs to Borrower or any
                                    Subsidiary of One Hundred Thousand

                                       5

<PAGE>   6

                                    Dollars ($100,000) or more; and (d) such
                                    budgets, sales projections, operating plans
                                    or other financial information as Bank may
                                    reasonably request from time to time.

                                            Within twenty-five (25) days after
                                    the last day of each month with respect to
                                    which either (i) Obligations under the
                                    Committed Revolving Line are outstanding, or
                                    (ii) Advances were made or Letters of Credit
                                    were issued, Borrower shall deliver to Bank
                                    a Borrowing Base Certificate signed by a
                                    Responsible Officer in substantially the
                                    form of EXHIBIT C hereto, together with aged
                                    listings of accounts receivable (by invoice
                                    date).

                                            Within forty-five (45) days after
                                    the last day of each quarter, Borrower shall
                                    deliver to Bank with the quarterly financial
                                    statements a Compliance Certificate signed
                                    by a Responsible Officer in substantially
                                    the form of EXHIBIT D hereto.

                                            Bank shall have a right from time to
                                    time hereafter to audit Borrower's Accounts
                                    at Borrower's expense (subject to Section
                                    2.5(c)), provided that such audits will be
                                    conducted no more often than every twelve
                                    (12) months unless an Event of Default has
                                    occurred and is continuing."

                  10.       The Loan Agreement shall be amended by deleting
                            Sections 6.8 and 6.9 in their entirety and inserting
                            in lieu thereof the following: 1.

                                    "6.8 ADJUSTED QUICK RATIO. Borrower shall
                                    maintain, as of the last day of each quarter
                                    with respect to which either (i) Obligations
                                    under the Committed Revolving Line are
                                    outstanding, or (ii) Advances were made or
                                    Letters of Credit were issued, a ratio of
                                    Quick Assets to Current Liabilities of at
                                    least 2.0 to 1.0. For calculation purposes
                                    of this Section 6.8, Current Liabilities
                                    shall (i) exclude "deferred maintenance
                                    revenue" and (ii) include all Credit
                                    Extensions under this Loan and Security
                                    Agreement.

                  11.      The Loan Agreement shall be amended by deleting the
                           following text appearing as the second sentence of
                           Section 7.2 entitled "Changes in Business, Ownership,
                           or Management, Business
                           Locations":

                                    "Borrower will not, without at least thirty
                                    (30) days prior written notification to
                                    Bank, issue any equity (other than in
                                    conjunction with stock-based awards granted
                                    under the Borrower's 1997 Stock Incentive
                                    Plan) relocate its chief executive office or
                                    add any new offices or business locations."

                           and inserting in lieu thereof the following:

                                       6

<PAGE>   7

                                   "Borrower will not, without at least thirty
                                    (30) days prior written notification to
                                    Bank, issue any equity which results in a
                                    material change in ownership or management
                                    (other than in conjunction with stock-based
                                    awards granted under the Borrower's Stock
                                    Incentive Plans), relocate its chief
                                    executive office or add any new offices or
                                    business locations."

                  12.      The Loan Agreement shall be amended by deleting the
                           following text appearing in Section 7.3 thereof
                           entitled "Mergers or Acquisitions":

                                    "and (iv) the aggregate purchase price for
                                    such transaction(s) will be a maximum amount
                                    of $1,000,000.00,"

                  13.      The Loan Agreement shall be amended by deleting the
                           following text appearing as Section 7.6 thereof:

                                    "7.6 DISTRIBUTIONS. Pay any dividends or
                                    make any other distribution or payment on
                                    account of or in redemption, retirement or
                                    purchase of any capital stock (other than
                                    distributions and payments made in
                                    conjunction with stock-based awards granted
                                    under the Borrower's 1997 Stock Incentive
                                    Plan)."

                           and inserting in lieu thereof the following:

                                    "7.6 DISTRIBUTIONS. Pay any dividends or
                                    make any other distribution or payment on
                                    account of or in redemption, retirement or
                                    purchase of any capital stock (other than
                                    distributions and payments made in
                                    conjunction with stock-based awards granted
                                    under the Borrower's Stock Incentive
                                    Plans)."

                  14.      The Loan Agreement shall be amended by inserting
                           therein the following text to appear as the last
                           paragraph of Section 9.1 entitled "Rights and
                           Remedies":

                                    "(k) Liquidate any Exchange Contracts not
                                    yet settled and demand that Borrower
                                    immediately deposit cash with Bank in an
                                    amount sufficient to cover any losses
                                    incurred by Bank due to liquidation of the
                                    Exchange Contracts at the then prevailing
                                    market price."

                  15.      The Borrower hereby ratifies, confirms and reaffirms,
                           all and singular, the terms and conditions of a
                           certain Negative Pledge Agreement dated as of March
                           26, 1998 between Borrower and Bank, and acknowledges,
                           confirms and agrees that said Negative Pledge
                           Agreement shall remain in full force and effect.

                  16.      The Borrowing Base Certificate appearing as EXHIBIT C
                           to the Loan Agreement is hereby replaced with the
                           Borrowing Base Certificate attached as EXHIBIT A
                           hereto.

                  17.      The Compliance Certificate appearing as EXHIBIT D to
                           the Loan Agreement is hereby replaced with the
                           Compliance Certificate attached as EXHIBIT B hereto.

4.       FEE. Borrower shall pay to Bank a modification fee equal to Thirty-One
Thousand Two Hundred Fifty Dollars ($31,250.00), which fee shall be due on the
date hereof and shall be deemed fully earned as of the date hereof.

                                       7

<PAGE>   8

5.       CONSISTENT CHANGES. The Existing Loan Documents are hereby amended
wherever necessary to reflect the changes described above.

6.       RATIFICATION OF LOAN DOCUMENTS. Borrower hereby ratifies, confirms, and
reaffirms all terms and conditions of all security or other collateral granted
to the Bank, and confirms that the indebtedness secured thereby includes,
without limitation, the Indebtedness.

7.       NO DEFENSES OF BORROWER. Borrower agrees that, as of this date, it has
no defenses against the obligations to pay any amounts under the Indebtedness.

8.       CONTINUING VALIDITY. Borrower understands and agrees that in modifying
the existing Indebtedness, Bank is relying upon Borrower's representations,
warranties, and agreements, as set forth in the Existing Loan Documents. Except
as expressly modified pursuant to this Loan Modification Agreement, the terms of
the Existing Loan Documents remain unchanged and in full force and effect.
Bank's agreement to modifications to the existing Indebtedness pursuant to this
Loan Modification Agreement in no way shall obligate Bank to make any future
modifications to the Indebtedness. Nothing in this Loan Modification Agreement
shall constitute a satisfaction of the Indebtedness. It is the intention of Bank
and Borrower to retain as liable parties all makers of Existing Loan Documents,
unless the party is expressly released by Bank in writing. No maker will be
released by virtue of this Loan Modification Agreement.

9.       JURISDICTION/VENUE. Borrower accepts for itself and in connection with
its properties, unconditionally, the non-exclusive jurisdiction of any state or
federal court of competent jurisdiction in the Commonwealth of Massachusetts in
any action, suit, or proceeding of any kind against it which arises out of or by
reason of this Loan Modification Agreement; provided, however, that if for any
reason Bank cannot avail itself of the courts of the Commonwealth of
Massachusetts, then venue shall lie in Santa Clara County, California.

10.      COUNTERSIGNATURE. This Loan Modification Agreement shall become
effective only when it shall have been executed by Borrower and Bank (provided,
however, in no event shall this Loan Modification Agreement become effective
until signed by an officer of Bank in California).

                                       8

<PAGE>   9

         This Loan Modification Agreement is executed as a sealed instrument
under the laws of the Commonwealth of Massachusetts as of the date first written
above.

BORROWER:                                   BANK:

ALLAIRE CORPORATION                         SILICON VALLEY BANK, doing
                                            business as SILICON VALLEY EAST

By: /s/ David A. Gerth                      By: /s/ Michael Tramack
    -----------------------------------         --------------------------------

Name: David A. Gerth                        Name: Michael Tramack
    -----------------------------------         --------------------------------

Title: CFO                                  Title: Assistant Vice President
    -----------------------------------         --------------------------------

                                            SILICON VALLEY BANK

                                            By: /s/ Michael Jordan
                                                --------------------------------

                                            Name: Michael Jordan
                                                --------------------------------

                                            Title: AVP
                                                --------------------------------
                                                (signed in Santa Clara County,
                                                 California)

                                       9
<PAGE>   10

                                    EXHIBIT A
                           BORROWING BASE CERTIFICATE

Borrower:    ALLAIRE CORPORATION                     Bank:   Silicon Valley Bank

Commitment Amount: $12,500,000.00, less the face amount of outstanding Letters
of Credit issued pursuant to Section 2.1.2

ACCOUNTS RECEIVABLE

1)       Accounts Receivable Book Value as of              $
                                              --------      --------------------
2)       Additions (please explain on reverse)             $
                                                            --------------------
3)       TOTAL ACCOUNTS RECEIVABLE                         $
                                                            --------------------

ACCOUNTS RECEIVABLE DEDUCTIONS (without duplication)

4)       Amounts over 90 days due                           $
                                                             -------------------
5)       Balance of 50% over 90 day accounts                $
                                                             -------------------
6)       Concentration Limits                               $
                                                             -------------------
7)       Foreign Accounts                                   $
                                                             -------------------
8)       Governmental Accounts                              $
                                                             -------------------
9)       Contra Accounts                                    $
                                                             -------------------
10)      Promotion or Demo Accounts                         $
                                                             -------------------
11)      Intercompany/Employee Accounts                     $
                                                             -------------------
12)      Other (please explain on reverse)                  $
                                                             -------------------
13)      TOTAL ACCOUNTS RECEIVABLE DEDUCTIONS               $
                                                             -------------------
14)      Eligible Accounts (#3 minus #13)                   $
                                                             -------------------
15)      LOAN VALUE OF ACCOUNTS (80.0% of #14)              $
                                                             -------------------

BALANCES

16)      Maximum Loan Amount                                $
                                                             -------------------
17)      Total Funds Available [Lesser of #16 or #15]       $
                                                             -------------------
18)      Present balance owing on Line of Credit            $
                                                             -------------------
19)      Outstanding under Sublimits (F/E)                  $
                                                             -------------------
20)      RESERVE POSITION (#17 minus #18 and #19)           $
                                                             -------------------

The undersigned represents and warrants that the foregoing is true, complete and
correct, and that the information reflected in this Borrowing Base Certificate
complies with the representations and warranties set forth in the Loan and
Security Agreement between the undersigned and Silicon Valley Bank.

COMMENTS:                            ==================================
                                                BANK USE ONLY
                                     ==================================
---------------------------
                                      RECEIVED BY:____________________
By: _______________________
       Authorized Signer              DATE:________________

                                      REVIEWED BY:____________________

                                      COMPLIANCE STATUS:  YES / NO

                                     ===================================

                                       10

<PAGE>   11

                                    EXHIBIT B
                             COMPLIANCE CERTIFICATE

TO:               SILICON VALLEY BANK

FROM:             ALLAIRE CORPORATION

         The undersigned authorized officer of ALLAIRE CORPORATION hereby
certifies that in accordance with the terms and conditions of the Loan and
Security Agreement between Borrower and Bank (the "Agreement"), (i) Borrower is
in complete compliance for the period ending _________ with all required
covenants except as noted below and (ii) all representations and warranties of
Borrower stated in the Agreement are true and correct in all material respects
as of the date hereof. Attached herewith are the required documents supporting
the above certification. The Officer further certifies that these are prepared
in accordance with Generally Accepted Accounting Principles (GAAP) and are
consistently applied from one period to the next except as explained in an
accompanying letter or footnotes. The Officer expressly acknowledges that no
borrowings may be requested by the Borrower at any time or date of determination
that Borrower is not in compliance with any of the terms of the Agreement, and
that such compliance is determined not just at the date this certificate is
delivered.

  PLEASE INDICATE COMPLIANCE STATUS BY CIRCLING YES/NO UNDER "COMPLIES" COLUMN.
<TABLE>
<CAPTION>

         REPORTING COVENANT                          REQUIRED                           COMPLIES
         ------------------                          --------                           --------
         <S>                                <C>                                          <C>   <C>
         Financial statements & CC          Quarterly 45 days                            Yes   No
         Annual (CPA Audited)               FYE within 120 days (w/ CC)                  Yes   No
         Monthly BBC & A/R Agings           Monthly within 25 days (when borrowing)      Yes   No
                        (by invoice date)

</TABLE>
<TABLE>
<CAPTION>

         FINANCIAL COVENANT                          REQUIRED                    ACTUAL       COMPLIES
         ------------------                          --------                    ------       --------

         <S>                                         <C>                         <C>           <C>   <C>
         Maintain (quarterly):

         Minimum Adjusted Quick Ratio                2.0:1.0 (when borrowing)    ____:1.0      Yes   No

         Minimum Tangible Net Worth                  $1,5000,000                 $________     Yes   No
                                                      (when borrowing)
</TABLE>

                                      ==================================
                                                 BANK USE ONLY
                                      ==================================

                                       RECEIVED BY:____________________

                                       DATE:________________

                                       REVIEWED BY:____________________

                                       COMPLIANCE STATUS:  YES / NO

                                      ===================================

COMMENTS REGARDING EXCEPTIONS:

Sincerely,

___________________    Date:_______________
SIGNATURE

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TITLE

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