<PAGE>
 
                                                                   Exhibit 10.20


  





                                OFFICE LEASE



                               by and between



                     Rosenberg SOMA Investments II, LLC
                                 (Landlord)

                                        
                                     and


                              USWeb Corporation
                                  (Tenant)
<PAGE>
 
                               TABLE OF CONTENTS



                                                                      Page



1.   The Premises                                                        4

2.   Term                                                                4

3.   Possession                                                          6

4.   Monthly Basic Rent/Parking Garage Rent                              8

5.   Operating Expenses                                                 11

6.   Security Deposit                                                   17

7.   Use.                                                               20

8.   Payments and Notices                                               22

9.   Brokers                                                            22

10.  Holding Over                                                       22

11.  Taxes on Tenant's Property                                         23

12.  Condition of Premises.                                             23

13.  Alterations                                                        24

14.  Repairs                                                            28

15.  Liens                                                              29

16.  Entry by Landlord                                                  29

17.  Utilities and Services                                             30

18.  Indemnification                                                    31

19.  Damage to Tenant's Property.                                       31
<PAGE>
 
20.  Insurance                                                          32

21.  Damage or Destruction                                              34

22.  Eminent Domain                                                     36

23.  Bankruptcy                                                         37

24.  Defaults and Remedies                                              37

25.  Assignment and Subletting                                          39

26.  Quiet Enjoyment                                                    42

27.  Subordination                                                      42

28.  Estoppel Certificate                                               42

29.  Rules and Regulations                                              43

30.  Conflict of Laws                                                   43

31.  Successors and Assigns                                             43

32.  Surrender of Premises                                              43

33.  Professional Fees                                                  43

34.  Performance by Tenant                                              44

35.  Mortgagee and Senior Lessor Protection                             44

36.  Definition of Landlord                                             44

37.  Waiver                                                             45

38.  Identification of Tenant                                           45

39.  Year 2000                                                          45

40.  Terms and Headings                                                 46

41.  Examination of Lease                                               46

                                     ii
<PAGE>
 
42.  Time                                                               46

43.  Prior Agreement; Amendments                                        46

44.  Severability                                                       46

45.  Recording                                                          46

46.  Limitation on Liability                                            46

47.  Riders                                                             46

48.  Signs                                                              47

49.  Modification for Lender                                            47

50.  Accord and Satisfaction                                            47

51.  Financial Statements                                               47

52.  Tenant as Corporation                                              48

53.  No Partnership or Joint Venture                                    48

54.  Rooftop Deck/Rooftop Antennae                                      48

55.  Option to Lease                                                    49

56.  Landlord's Representations                                         49

57.  Arbitration                                                        50


                                     iii
<PAGE>
 
                                  OFFICE LEASE

This Office Lease ("Lease"), dated March 5, 1999 (the "Effective Date"), is made
and entered into by and between Rosenberg SOMA Investments II, LLC, a Delaware
limited liability company ("Landlord") and USWeb Corporation, a Delaware
corporation ("Tenant").

1. The Premises.
   ------------

1.1  Landlord hereby leases to Tenant, and Tenant hereby leases from Landlord,
the Premises designated in the Summary and as outlined on the Floor Plan 
attached hereto as Exhibit "A" in the building at the address designated
                   -----------
in the Summary (the "Building"), located on the parcel of real property (the
"Site") under the Building, subject to those rules and regulations attached
hereto as Exhibit D, and such additional reasonable rules and regulations as 
          ---------                                                 
Landlord may deliver in writing to Tenant from time to time. Tenant
acknowledges that Landlord has made no representation or warranty regarding
the condition of the Premises, Building, or Site except as specifically stated
in this Lease. The parties hereto agree that Tenant's leasing of the Premises
is upon and subject to the terms, covenants and conditions herein set forth
and Tenant covenants as a material part of the consideration for this Lease to
keep and perform each and all of said terms, covenants and conditions by it to
be kept and performed and that this Lease is made upon the condition of such
performance.

1.2  The rights and obligations of the parties regarding the construction of
the Premises are described in Paragraphs 2 and 3 of this Lease, and in the
Work Letter ("Work Letter") attached as Exhibit E. Any inconsistency between
                                        ---------               
the provisions of the Work Letter and the provisions of the balance of the
Lease shall be governed by the provisions of the Work Letter.

1.3  The Premises as described herein shall include the right of Tenant to use
the loading dock and storage rooms adjacent to the loading dock. The
obligations of Tenant with respect to the Premises as provided in this Lease
shall be applicable to the loading dock and to the storage areas adjacent to
the loading dock as well as to the remainder of the Premises.

1.4  References in this Lease to "rentable square feet", "rentable square
footage" and "rentable area" shall have the same meanings, and Tenant hereby
acknowledges and agrees that the rentable square footage of the Premises shall
be deemed, and is, 74,686 rentable square feet. No adjustment in the Monthly
Basic Rent, Tenant's Percentage Share, any monetary or other obligation of
Tenant, or any other term of this Lease shall be made by reason of any
discrepancy in the rentable square footage which is later discovered.


2. Term.
   ----

2.1  Subject to Paragraphs 2.2 and 3.1, the term of this Lease ("Term") shall
commence on the Lease Commencement Date, and terminate on the Lease Expiration
Date, as such terms are defined in the Summary, unless the Term is earlier
terminated as hereinafter provided. Landlord shall provide Tenant, and
Tenant's consultant's and contractors, with access to the Premises at least
fourteen (14) days prior to the anticipated Lease Commencement Date for
purposes of installation by Tenant of its fixtures,
<PAGE>
 
equipment, wiring, furniture and other similar matters. In connection with any
such early entry by Tenant, Tenant and its consultants and contractors shall
not interfere with the completion of construction by Landlord of the
Landlord's Work and the Tenant's Improvements (as defined below). At all times
that Tenant has access to the Premises, the provisions of this Lease shall be
applicable, provided only that the obligation of Tenant to pay Monthly Basic
Rent, Parking Lot Rent and Operating Rent (as defined below) shall not
commence until the Lease Commencement Date.

2.2  Landlord shall substantially complete the initial, base improvements
to the Building and the Premises, as required of Landlord pursuant to the
terms of the Work Letter, ("Landlord's Work") and shall further substantially
complete the Tenant's Improvements ("Tenant's Improvements") as described in
the Work Letter on or before July 7, 1999. The Lease Commencement Date shall
be July 7, 1999 as specified in the Summary, subject, however, to deferral
pursuant to the provisions of Paragraph 3.1 below. The actual Lease
Commencement Date shall be specified in Landlord's Notice of Lease Term Dates
("Notice"), in the form of Exhibit "B" attached hereto, and shall be served 
                           -----------                              
upon Tenant as provided in Paragraph 8, as soon as Landlord determines that
the Landlord's Work and the Tenant's Improvements have been substantially
completed as provided in Paragraph 3.1 below. The Notice shall be binding upon
Tenant unless Tenant objects to the Notice in writing, served upon Landlord as
provided in Paragraph 8, within five (5) business days of Tenant's receipt of
the Notice.

2.3  Tenant shall have two (2) consecutive options (the "Extension Options";
each an "Extension Option") to extend the Term, each for a five (5) year
period (the "First Extended Term" and "Second Extended Term", respectively;
each an "Extended Term") on all the terms and conditions contained in this
Lease with the exception of the Monthly Basic Rent and the Base Year which
shall be adjusted pursuant to the provisions of Paragraphs 4.2 and 5.1 below.
Upon commencement of the First Extended Term, the only remaining option to
extend the Term shall be the Second Extended Term, and upon exercise of the
option with respect to the Second Extended Term, no further right to extend
the Term shall exist. In the event Tenant fails to timely exercise the option
for the First Extended Term, Tenant's option for the Second Extended Term
shall be void. In order to exercise an Extension Option, Tenant shall deliver
written notice of its exercise of the option ("Option Notice") to Landlord at
least two hundred twenty-five (225) days but not more than one (1) year before
the expiration of the initial Term or First Extended Term, as the case may be.
The Extension Options shall be subject to the following terms and conditions:

(a)     An Extension Option may be exercised only by delivery of the Option
Notice as provided in this Paragraph and only if, as of the date of delivery
of the Option Notice, Tenant is not in default, beyond applicable cure
periods, under this Lease.
(b)
(c)     The rights contained in this Paragraph shall be personal to the
originally named Tenant and may be exercised only by the originally named
Tenant (and not any assignee, sublessee, or other transferee of Tenant's
interest in this Lease other than a Permitted Transferee as defined in
Paragraph 25 below) and only if the originally named Tenant (or Permitted
Transferee) occupies the entire Premises as of the date it exercises an
Extension Option in accordance with the terms of this Paragraph.
(d)
(e)     If Tenant properly exercises an Extension Option and is not in
default, beyond applicable 
<PAGE>
 
cure periods, under this Lease at the end of the initial Term (or the First
Extended Term, as the case may be), the Term shall be extended for the
applicable Extended Term. 
(f) 
(g) References in this Lease to the "Term" shall
include the initial Term of ten (10) years and shall, in addition, include the
First Extended Term and the Second Extended Term, as applicable. 
(h)

2.4  For purposes of this Lease the term "Lease Year" shall mean each
consecutive twelve (12) month period during the Term provided that (i) the
first Lease Year commences on the Lease Commencement Date and ends on the last
day of the calendar year (December 31st) in which the Lease Commencement Date
falls; (ii) the second and each succeeding Lease Year commences on the first
day of the next calendar year; and (iii) the last Lease Year ends on the Lease
Expiration Date or earlier date of termination.


3. Possession.
   ----------

3.1  Tenant agrees that in the event Landlord is unable to deliver possession
of the Premises to Tenant, with Landlord's Work and the Tenant's Improvements
having been substantially completed on or before July 7, 1999, this Lease
shall not be void or voidable, nor shall Landlord be liable to Tenant for any
loss or damage resulting therefrom. In the event that Landlord fails to
deliver the Premises to Tenant with Landlord's Work and Tenant's Improvements
substantially completed on or before July 7, 1999, the Lease Commencement Date
shall be extended to the date on which Landlord delivers the Premises to
Tenant with Landlord's Work and Tenant's Improvements substantially completed
subject to the limitations as provided in Paragraph 3.2 below. For purposes
hereof, Landlord's Work and Tenant's Improvements shall be considered as
having been substantially completed (i) upon completion in all material
respects of Landlord's Work and the Tenant's Improvements as certified by
Landlord's architect as identified in the Work Letter ("Landlord's Architect")
subject only to such punch list items as may have been identified by
Landlord's Architect or by Tenant pursuant to the provisions of Paragraph 12
below, and (ii) upon Landlord obtaining all governmental approvals and
occupancy certificates required for the legal occupancy of the Building
(collectively, "Government Approvals").

3.2  Notwithstanding the provisions of Paragraph 3.1 to the contrary, any
extension of the Lease Commencement Date in accordance with the provisions of
Paragraph 3.1 shall be reduced by the aggregate number of days of Tenant Delay
(as defined below).  By way of example, if pursuant to the provisions of
Paragraph 3.1 the Lease Commencement Date occurs on July 17, 1999 but there is
an aggregate number of ten (10) days of Tenant Delay, then notwithstanding the
provisions of Paragraph 3.1, the Lease Commencement Date (and the obligation of
Tenant to pay Monthly Basic Rent, Parking Lot Rent and Operating Rent) shall
commence as of July 7, 1999.  A delay by Tenant ("Tenant Delay") shall occur
upon: (i) Tenant's failure to perform any obligation of Tenant to be performed
under the Work Letter on or before the date or within the time period set forth
in the Work Letter including, without limitation, any failure by Tenant to
timely satisfy a Tenant Benchmark (as defined in the Work Letter); (ii) any
change by Tenant in the Construction Drawings (as defined in the Work Letter)
which Tenant has previously approved or a change by Tenant in the work to be
performed in connection with the Tenant's Improvements from that work otherwise
specified in the Construction Drawings, which change results in a delay in the
construction of the Tenant's Improvements; (iii) failure of Tenant to timely pay
on or before 
<PAGE>
 
the date required all amounts required to be paid by Tenant as provided in the
Work Letter; or (iv) any other delay caused by Tenant or Tenant's Architect in
connection with the design, construction or bidding process with respect to
the Tenant's Improvements including, without limitation, the failure by Tenant
or Tenant's Architect to promptly respond to reasonable requests from the
Contractor (as defined in the Work Letter) for clarification and/or additional
detail relating to the work to be performed pursuant to the Construction
Drawings. The period of any Tenant Delay with respect to the matters described
in Clauses (i) or (iii) above, shall be the number of days from the date on
which the matter was to be performed by Tenant through and including the day
on which the matter is fully cured and performed by Tenant and the number of
days of any Tenant Delay as specified in Clauses (ii) and Clause (iv) above
shall be equal to the number of days of delay in the performance of the work
in connection with the Tenant's Improvements resulting from the failure by
Tenant or by Tenant's consultants or representatives or the delay resulting
from any change made by Tenant as described in Clause (ii). In the event that
Landlord during the construction of Tenant's Improvements asserts that a
Tenant Delay has occurred, Landlord shall give written notice of such asserted
Tenant Delay to Tenant and to Tenant's Architect as defined in the Work Letter
("Tenant's Architect") which notice ("Delay Notice") shall state specifically
the nature of the purported Tenant Delay. In the event that Landlord fails to
give a Delay Notice within five (5) business days following the occurrence of
the asserted Tenant Delay, Landlord shall be deemed to have waived such
asserted delay and shall thereafter not be entitled to assert such Tenant
Delay in connection with the provisions of this Paragraph 3.2. In the event
that Landlord timely gives a Delay Notice and Tenant disagrees with the
assertion of the claimed delay by giving written notice of such disagreement
to Landlord within five (5) business days following the date on which the
Delay Notice is given, then within ten (10) days following the substantial
completion of the Landlord's Work and the Tenant's Improvements as evidenced
by the certificate of Landlord's architect and receipt of the Government
Approvals (collectively, "Completion Certificate"), Landlord's Architect and
Tenant's Architect shall attempt to come to an agreement, which agreement
shall be binding on Landlord and Tenant, as to whether any Tenant Delay has
occurred and the number of days of such Tenant Delay. A copy of the Completion
Certificate shall be given by Landlord to Tenant which, with respect to the
Government Approvals, shall consist of the certificate of occupancy. In the
event that Landlord's Architect and Tenant's Architect are unable to so agree
within twenty (20) days following the date on which the Landlord's Completion
Certificate is given to Tenant then the issue of the occurrence and the extent
of any delay caused by Tenant shall be subject to arbitration in accordance
with the provisions of Paragraph 57. In the event that Tenant fails to object
to any Delay Notice given by Landlord by timely giving written notice of such
objection to Landlord, Tenant shall be considered to have approved the Tenant
Delay as set forth in the Delay Notice. In the event that a final
determination with respect to the occurrence of any Tenant Delay as provided
in this Paragraph 3.2 has not occurred on or before the date asserted by
Landlord to be the Lease Commencement Date (taking into account any Tenant
Delay as asserted by Landlord) then the Lease Commencement Date shall be
considered to have occurred on the date as provided in the Summary and in
accordance with the provisions of Paragraphs 2.2 and 3.1 subject to adjustment
as asserted by Landlord pursuant to the provisions of this Paragraph 3.2. In
the event that subsequent to such date it is finally determined that a further
delay in the occurrence of the Lease Commencement Date should have occurred by
reason of the provisions of Paragraph 3.1 and the provisions of this Paragraph
3.2, then Tenant shall be entitled to a credit in an amount equal to the per
day amount in connection with the Monthly Basic Rent, the Parking Lot Rent and
the Operating Rent as then having been paid by Tenant for the period of the
additional delay as finally determined pursuant to the provisions of this
Paragraph 3.2. 
<PAGE>
 
Such credit shall be applied against the next payment of Monthly Basic Rent,
Parking Lot Rent and/or Operating Rent as then due pursuant to this Lease from
Tenant to Landlord.

3.3  Notwithstanding anything in the foregoing Paragraphs to the contrary, if
the Landlord's Work and the Tenant's Improvements are not substantially
completed (as evidenced by a Completion Certificate) on or before December 1,
1999, then Tenant shall have the right to terminate this Lease by written notice
given to Landlord at any time prior to the date a certificate of occupancy is
obtained for the Premises.  Termination of the Lease hereunder shall be Tenant's
sole remedy in the event of a failure of delivery of possession of the Premises
to Tenant.


4. Monthly Basic Rent/Parking Garage Rent.
   --------------------------------------

4.1  Tenant agrees to pay to Landlord as Monthly Basic Rent for the Premises the
Monthly Basic Rent designated in the Summary for each respective period
("Monthly Basic Rent"), each in advance on the first day of each and every
calendar month during said Term, except that the first month's Monthly Basic
Rent shall be paid upon the execution hereof.  In the event the Term of this
Lease ends on a day other than the last day of a calendar month, then the rental
for such period shall be prorated in the proportion that the number of days this
Lease is in effect during such period bears to thirty (30), and such rental
shall be paid at the commencement of such period.  In the event that the Lease
Commencement Date occurs other than on the first day of a calendar month, and
the full first month's Monthly Basic Rent has been previously paid as provided
in this Lease, then the rent for the initial partial calendar month commencing
as of the Lease Commencement Date shall be prorated in the proportion that the
number of days this Lease is in effect during such calendar  month bears to
thirty (30) and the prepaid first month's Monthly Basic Rent shall be applied to
such prorated amount with the balance of the prepaid first month's Monthly Basic
Rent being applied to reduce the payment of Monthly Basic Rent to be paid on the
first day of the first full calendar month of the Term of this Lease.  In
addition to said Monthly Basic Rent, Tenant agrees to pay the amount of the
rental adjustments as and when provided in this Lease.  Said Monthly Basic Rent
and all additional rent including, without limitation, Parking Lot Rent and
Operating Rent, shall be paid to Landlord, without any prior demand therefor and
without any deduction or offset whatsoever in lawful money of the United States
of America, which shall be legal tender at the time of payment, at the address
of Landlord designated in Subparagraph (c) of the Summary or to such other
person or at such other place as Landlord may from time to time designate in
writing.  Further, all charges to be paid by Tenant hereunder, including,
without limitation, payments for repairs and other costs and expenses shall be
considered additional rent for the purposes of this Lease, and the word "rent"
in this Lease shall include such additional rent as well as Monthly Basic Rent,
Parking Lot Rent and Operating Rent unless the context specifically or clearly
implies that only the Monthly Basic Rent, Parking Lot Rent and/or Operating Rent
is referenced.  Tenant shall deliver to Landlord as prepaid rent that amount set
forth in the Summary upon execution of this Lease.

4.2  In the event Tenant exercises either of the options to extend the Term
pursuant to the provisions of Paragraph 2.3, the Monthly Basic Rent shall be
adjusted at the commencement of each Extended Term to reflect the then-fair
market rental value of the Premises pursuant to the terms of this Paragraph.
The fair market rental value of the Premises shall be determined in good faith
by Landlord, who shall notify Tenant of such determination in writing within
thirty (30) days of receipt of the Option Notice.  If Tenant 
<PAGE>
 
does not agree with Landlord's determination, Tenant shall deliver written
notice of Tenant's objection to Landlord within fifteen (15) days of receipt
of notice from Landlord, or Landlord's determination of the fair market rental
value shall be final. If Tenant timely objects to Landlord's determination,
Landlord and Tenant shall diligently attempt in good faith to agree on the
fair market rental value of the Premises on or before the tenth (10th) day
following delivery of Tenant's written objection to Landlord's determination
(the "Outside Agreement Date"). If Landlord and Tenant are unable to agree on
the new Monthly Basic Rent by the Outside Agreement Date, the fair market
rental value of the Premises shall be determined by appraisal. Landlord and
Tenant shall first attempt to select a mutually agreeable appraiser to conduct
the appraisal, which appraiser's conclusion shall be binding on the parties.
In the event they are unable to agree on one appraiser within ten (10) days of
the Outside Agreement Date, the parties shall each select an appraiser within
twenty (20) days of the Outside Agreement Date, who together shall attempt to
determine the fair market rental value of the Premises. If either party fails
to appoint an appraiser within such time period, the appraiser timely
appointed by the other party shall be the sole appraiser, whose determination
shall be binding on both parties. If two appraisers are timely appointed, but
they are unable to agree on the fair market rental value of the Premises
within fifty (50) days of the Outside Agreement Date, they shall mutually
select a third appraiser and the three appraisers shall each submit their
appraisal of the fair market rental value of the Premises within thirty (30)
days of selection of the third appraiser. The fair market rental value of the
Premises shall be the average of the three appraisals; provided, however, that
if either the high or low appraisal differs from the middle appraisal by ten
percent (10%) or more, it shall be disregarded and the two remaining
appraisals shall be averaged to determine the fair market rental value. If
both the high and low appraisals differ from the middle appraisal by ten
percent (10%) or more, then both shall be disregarded, and the fair market
rental value of the Premises shall be as determined by the middle appraisal.
Each party shall bear the cost of their respective appraisers; if a third
appraiser is necessary, the parties shall share equally the cost of the third
appraiser. All appraisers shall be MAI qualified appraisers, and shall have a
minimum of five (5) years experience in the appraisal of commercial properties
in the San Francisco Bay Area and no appraiser shall have worked previously
for Landlord or Tenant in any capacity. The fair market rental value shall be
based on comparable space in San Francisco, which shall (i) not be subleased,
(ii) shall be comparable in size, location and quality with the Premises,
(iii) shall be leased for a term comparable to the subject option term (five
years), and (iv) shall take into account the value of any rent abatement,
tenant improvement allowances or other concessions given to the tenant of the
comparable space. The Monthly Basic Rent shall be adjusted to reflect the fair
market rental value, as so determined. The Base Year for each Extended Term
shall be adjusted as set forth in Paragraph 5.1 below.

4.3  In addition to the Monthly Basic Rent, Tenant shall pay an additional
monthly rental amount (the "Parking Lot Rent") for Tenant's exclusive use of the
parking garage (the "Garage") located in the basement of the Building.  The
Parking Lot Rent shall be payable, in advance, on the first  day of each and
every calendar month during the Term with amounts  payable for any partial month
to be prorated in proportion to the number of days that this Lease is in effect
during such period bears to thirty (30) with such rental to be paid at the
commencement of such period.  The Garage shall constitute a portion of the
Premises and shall be subject to all terms and conditions of this Lease.  During
the Term, Landlord shall provide a parking valet/attendant on all business days
during the hours of 8:00 a..m. to 6:00 p.m.  Tenant, at its election, shall be
entitled to request Landlord to adjust the hours during which valet/attendant
parking is provided so that such hours commence one (1) hour earlier or one (1)
hour later, and end one 
<PAGE>
 
(1) hour earlier or one (1) hour later, as the case may be, provided that, in
all events, Landlord shall not be obligated to provide valet/attendant parking
for in excess of ten (10) hours and further provided that any adjustment in
such hours requested by Tenant shall be subject to compliance with any
collective bargaining agreements then in effect with respect to the employees
providing parking and any excess cost incurred by reason of any such
adjustment in the hours shall be borne solely by Tenant. It is agreed that the
number of vehicles which can be reasonably valet parked in the Garage is sixty
(60), subject to an increase or decrease to a maximum of seventy (70) and a
minimum of fifty-four (54) which increase or decrease shall be subject to the
reasonable determination of Landlord and Tenant. Entrance to the Garage shall
be pursuant to a card key access system. Prior to the Lease Commencement Date,
Landlord shall substantially complete installation of a card key reader
apparatus at the Garage entrance facing Bluxome Street which shall allow 24
hour/7days per week access to the Garage via the use of magnetic card keys.
The Parking Lot Rent which Tenant shall pay to Landlord shall be the product
of the sum of Two Hundred Dollars ($200.00) multiplied by the number of
vehicles which can be reasonably valet parked in the Garage. The Parking Lot
Rent shall be adjusted upward on an annual basis, commencing on the first day
(the "First Adjustment Date") of the calendar month following the first
anniversary of the Lease Commencement Date and continuing thereafter on each
subsequent anniversary of the First Adjustment Date thereafter (each, an
"Adjustment Date") throughout the initial ten (10) year Term of this Lease, by
an amount equal to four percent (4%) of the Parking Lot Rent in effect for the
month immediately preceding the subject Adjustment Date. Thereafter during the
Extended Terms (if applicable), in the reasonable discretion of Landlord, the
Parking Lot Rent shall be periodically adjusted upward to reflect then-current
market conditions. In no event shall the Parking Lot Rent be decreased from
the Parking Lot Rent in effect for the month immediately preceding any
applicable Adjustment Date.

     In the event that Landlord and Tenant are unable to agree upon the amount
of the increase or decrease in the number of vehicles which can be reasonably
valet parked in the Garage within ten business days following the written
request of either given to the other ("Outside Parking Date"), then the amount
of such increase or decrease shall be determined by a third party parking
company experienced in the valet parking of vehicles. The right to request a
determination by a third party parking company (or companies) as described in
this Paragraph shall be a one-time right and after exercise by either Landlord
or Tenant shall thereafter not be further exercisable by either Landlord or
Tenant. Landlord and Tenant shall first attempt to select a mutually agreeable
parking company to conduct a review of the Garage and determine on a basis
binding on both parties the amount of increase or decrease in the number of
vehicles which can be reasonably valet parked in the Garage (referred to as
the "Amount of Adjustment"). In the event Landlord and Tenant are unable to
agree on a parking company within ten (10) days of the Outside Parking Date,
the parties shall each select a parking company within twenty (20) days of the
Outside Parking Date, who together shall attempt to determine the Amount of
Adjustment. If either party fails to appoint a parking company within such
time period, the parking company timely appointed by the other party shall be
the sole parking company, whose determination shall be binding on both
parties. If two parking companies are timely appointed but they are unable to
agree on the Amount of Adjustment within forty (40) days of the Outside
Parking Date, they shall mutually select a third parking company and the three
parking companies shall each submit their determination of the Amount of
Adjustment within ten (10) business days following the selection of the third
parking company. The Amount of Adjustment shall be the average of the three
determinations, provided, however, that if either the high or low
determination differs from the middle determination by 10% or more, it shall
be disregarded and the two remaining 
<PAGE>
 
determinations shall be averaged to determine the Amount of Adjustment. If
both the high and low determinations differ from the middle determination by
10% or more, then both shall be disregarded, and the Amount of Adjustment
shall be as determined by the middle parking company. Each party shall bear
the cost of its respective parking company; if a third parking company is
necessary, the parties shall share equally the cost of the third parking
company. All parking companies shall have a minimum of five (5) years
experience in the management and operation of valet parking lots and/or
garages and no parking company shall have previously worked for either the
Tenant or the Landlord.

     If the Amount of Adjustment is determined subsequent to the Lease
Commencement Date, the Parking Lot Rent payable as of the Lease Commencement
Date shall be based upon the number of sixty (60) vehicles.  In the event that
it is finally determined that an adjustment is required, then the Parking Lot
Rent payable on the first day of the next succeeding calendar month and
thereafter, shall be based upon the number of vehicles as so adjusted.  In
addition, in the event that the Amount of Adjustment results in an increase in
the number of vehicles from the initially determined sixty (60), then within
twenty (20) days following receipt by Landlord and Tenant of final determination
of such Amount of Adjustment, Tenant shall pay to Landlord the amount of
additional Parking Lot Rent attributable to such adjustment based upon Two
Hundred Dollars ($200) per month per additional vehicle (pro rated if necessary
on the basis of a partial month).  In the event that the Amount of Adjustment
results in a decrease in the number of vehicles from the initial sixty (60),
then Tenant shall be entitled to a credit against the next Parking Lot Rent then
due based upon such decrease in the number of vehicles at a rent of Two Hundred
Dollars ($200) per vehicle per month (with any partial month to be pro rated).

     Tenant shall, from time to time, at its cost, be entitled to construct
storage areas within the Garage provided that such areas are constructed in
accordance with all applicable law and regulations and that such construction is
subject to Landlord's reasonable review.  Notwithstanding the construction of
any one or more of such storage areas, the Parking Lot Rent otherwise payable by
Tenant as provided above in this Paragraph 4.3 shall not be subject to reduction
regardless of whether or not the construction of any storage areas within the
Garage reduces the number of vehicles which can be valet parked in the Garage.

4.4  The aggregate of the Monthly Basic Rent and the Parking Lot Rent from time
to time to be paid pursuant to the provisions of this Lease may sometimes be
referred to as the "Aggregate Monthly Basic Rent".  The Aggregate Monthly Basic
Rent shall be payable in advance on the first day of each and every calendar
month during the Term as provided herein in connection with the Monthly Basic
Rent and the Parking Lot Rent, respectively.

4.5  All payments received by Landlord from Tenant for Monthly Basic Rent,
Parking Lot Rent, Operating Rent or any other sums due under this Lease shall be
applied to the oldest payment obligation owed by Tenant to Landlord.  No
designation by Tenant, either in a separate writing or on a check or money
order, shall modify this clause or have any force or effect.


5. Operating Expenses.
   ------------------

5.1  For the purposes of this Subparagraph 5.1, the following terms are defined
as follows:
<PAGE>
 
        Tenant's Percentage Share.  Tenant's Percentage Share shall mean the
        -------------------------                                           
percentage set forth in the Summary.

        Base Year.  Base Year shall mean the year set forth in the Summary;
        ---------                                                          
provided, however, that should Tenant exercise its option for the First Extended
Term and/or the Second Extended Term, then the Base Year for the applicable
Extended Term shall be revised to mean the calendar year in which the applicable
Extended Term commences.

        Operating Expenses.  Operating Expenses shall consist of all costs of
        ------------------                                                   
operation and maintenance of the Building, the common areas and the Site as
determined by standard accounting practices, calculated assuming the Building is
ninety-five percent (95%) occupied (unless actually occupied in a greater
percentage, in which case the actual occupancy percentage shall be used),
including the following costs by way of illustration, but not limitation: real
property taxes and assessments and any taxes or assessments hereafter imposed in
lieu thereof; gross receipt taxes (whether assessed against Landlord or assessed
against Tenant and collected by Landlord, or both); the net cost and expense of
insurance for which Landlord is responsible hereunder or which Landlord or any
first mortgagee with a lien affecting the Premises reasonably deems necessary in
connection with the operation of the Building (including the deductible portion
of any insured loss); janitorial services; security; parking valet/attendant
expenses; card key parking apparatus repair and maintenance; any and all Garage-
related expenses, with all such valet/attendant, car key apparatus repair,
maintenance and other Garage-related expenses not to exceed such expenses
incurred by prudent operators of substantially similar sized garages within the
geographical location of the Premises; labor; utilities and utilities
surcharges, and any other costs levied, assessed or imposed by, or at the
direction of, or resulting from statutes or regulations or interpretations
thereof, promulgated by any federal, state, regional, municipal or local
government authority in connection with the use or occupancy of the Building or
the Premises or the parking facilities serving the Building or the Premises; the
cost (amortized over the useful life of the improvement or equipment in question
as reasonably determined by Landlord in accordance with generally accepted
accounting principles at a capitalization rate of ten percent (10%) of (a) any
capital improvements made to the Building by the Landlord which are reasonably
anticipated to increase the efficiency of the Building or made to the Building
by Landlord that are required under any governmental law or regulation that was
not applicable to the Building at the time it was constructed, or (b)
replacement of any building equipment needed to operate the Building at the same
quality levels (or levels of efficiency) as prior to the replacement; costs
incurred in the management of the Building, if any (including supplies, wages
and salaries of employees used in the management, operation and maintenance of
the Building, and payroll taxes and similar governmental charges with respect
thereto); on site Building management office rental; a management fee (not to
exceed 3% of the gross revenue receivable by Landlord from time to time in
connection with the Premises pursuant to this Lease); air conditioning; waste
disposal; heating; ventilating; elevator maintenance; supplies; materials;
equipment; tools; repair and maintenance of the structural portions of the
Building and the plumbing, heating, ventilating, air conditioning and electrical
systems installed or furnished by Landlord; and maintenance, costs and upkeep of
all parking and common areas, rental of personal property used in maintenance;
costs and expenses of gardening and landscaping, maintenance of signs (other
than Tenant's signs); personal property taxes levied on or attributable to
personal property used in connection with the entire Building, including the
common areas; reasonable audit or verification fees; and costs and expenses of
repairs, resurfacing, repairing, maintenance, painting, lighting, cleaning,
<PAGE>
 
window washing, refuse removal, security and similar items, including
appropriate reserves.

     Notwithstanding anything contained in this Paragraph 5.1 to the contrary,
Operating Expenses shall not include any of the following:

(a)     electrical, water, sewer, gas, garbage, and janitorial costs (including
janitorial supplies) with respect to the Premises which are to be paid directly
by Tenant or reimbursed to Landlord as having been separately billed by Landlord
to Tenant as provided in Paragraph 5.2 below;

(b)     depreciation on the Building or equipment therein;

(c)     Landlord's executive salaries;

(d)     real estate brokers' commissions;

(e)     interest expense on Building financing;

(f)     amortization of cost of tenant improvements in the Building;

(g)     ground rent;

(h)     income and franchise taxes;

(i)     Landlord's cost of electricity or other service sold to tenants to the
extent Landlord is reimbursed therefore as a charge over the Monthly Basic Rent
and any additional rent payable under the lease with that tenant;

(j)     third party accountants' fees, attorneys' fees and other professional
fees and costs incurred in connection with disputes or lease negotiations with
tenants or other occupants or prospective tenants or occupants of the
Building, the enforcement of any leases (including unlawful detainer
proceedings and the collection of rents), other than de minimis amounts, and
requests to assign or sublet;

(k)     overhead and profit paid to subsidiaries or affiliates of the Landlord
for management or other services on or to the Building for supplies or other
materials, to the extent that the overall cost of the services, supplies or
materials provided by Landlord materially exceeds the competitive cost of the
services, supplies, or materials if obtained from an unrelated third party on
an arm's length basis;

(l)     compensation paid to clerks, attendants, or other persons in commercial
concessions operated by the Landlord;

(m)     rentals and other related expenses incurred in leasing air conditioning
systems, elevators, or other equipment ordinarily considered to be of a capital
nature;

(n)     items and services for which Tenant reimburses the Landlord or pays
third parties or that the Landlord provides selectively to one or more tenants
of the Building other than Tenant without 
<PAGE>
 
reimbursement;

(o)     maintenance costs incurred in connection with repairs or other work
needed because of fire, windstorm, or other casualty or cause insured against
by Landlord or to the extent Landlord's insurance required under the terms of
the Lease would have provided insurance, whichever is greater;

(p)     all voluntary contributions to any political or charitable
organizations or other industry related associations (e.g., BOMA);

(q)     capital costs for the acquisition of sculpture, paintings or other art
objects;

(r)     advertising, marketing and promotion costs;

(s)     costs associated with the operation of the corporation or other entity
which constitutes the Landlord, as distinguished from costs of operation of the
Building, including accounting and legal costs, costs of defending lawsuits with
any mortgagee, and the costs of selling, syndicating, financing, mortgaging or
hypothecating any ownership interest in Landlord, or any of the Landlord's
interests in the Building;

(t)     costs that are actually reimbursed to the Landlord by insurance
companies or other third parties; provided that the Landlord shall use
commercially reasonable efforts to pursue payment from such insurance
companies or other third parties (the costs of such efforts to procure payment
to be included as an Operating Expense);

(u)     reserves for capital items, bad debts, or rental losses;

(v)     the costs incurred to investigate the presence of any Hazardous
Material (as defined below), costs to respond to any claim of Hazardous
Material contamination or damage, costs to remove any Hazardous Material from
the Premises, Building or Site or to remediate any Hazardous Material
contamination, any judgments or other costs incurred in connection with any
Hazardous Material exposure or release, except to the extent that the cost is
caused by the storage, use, release or disposal of the subject Hazardous
Material by Tenant;

(w)     fines and penalties incurred due to Landlord's operation of the
Building in violation of applicable laws or due to Landlord's failure to
timely pay real property taxes;

(x)     except to the extent expressly permitted, any repairs of a capital
nature or costs for items that would normally be capitalized under generally
accepted accounting principles; and

(y)     interest, charges and fees incurred with respect to mortgage financing
for the Building or Site.

     As used herein, the term "real property taxes" shall include any form of
assessment, license fee, license tax, business license fee, tax, levy, charge,
or similar imposition, imposed by any authority having 
<PAGE>
 
the direct power to tax, including any city, county, state or federal
government, or any school, agricultural, lighting, drainage or other
improvement or special assessment district thereof, as against any legal or
equitable interest of Landlord in the Premises, including, but not limited to,
the following:

     (i)   any tax on Landlord's "right" to rent or "right" to other income from
the Premises or as against Landlord's business of leasing the Premises;

     (ii)  any assessment, tax, fee, levy or charge in substitution, partially
or totally, of any assessment, tax, fee, levy or charge previously included
within the definition of real estate tax, it being acknowledged by Tenant and
Landlord that Proposition 13 was adopted by the voters of the State of
California in the June, 1978 Election and that assessments, taxes, fees, levies
and charges may be imposed by governmental agencies for such services as fire
protection, street, sidewalk and road maintenance, refuse removal and for other
governmental services formerly provided without charge to property owners or
occupants.  It is the intention of Tenant and Landlord that all such new and
increased assessments, taxes, fees, levies and charges be included within the
definition of "real property taxes" for the purposes of this Lease;

     (iii) any assessment, tax, fee, levy or charge allocable to or measured
by the area of the Premises or the rent payable hereunder, including, without
limitation, any excise tax levied by the State, City or Federal government, or
any political subdivision thereof, with respect to the receipt of such rent, or
upon or with respect to the possession, leasing, operating, management,
maintenance, alteration, repair, use or occupancy by Tenant of the Premises, or
any portion thereof;

     (iv)  any assessment, tax, fee, levy or charge upon this transaction or any
document to which Tenant is a party, creating or transferring an interest or an
estate in the Premises;

     (v)   any assessment, tax, fee, levy or charge by any governmental agency
related to any transportation plan, fund or system instituted within the
geographic area of which the Building is a part; or

     (vi)  reasonable legal and other professional fees, costs and disbursements
incurred in connection with proceedings to contest, determine or reduce real
property taxes.

     Notwithstanding any provision of this Paragraph 5.1 expressed or implied to
the contrary, "real property taxes" shall not include Landlord's federal or
state income, franchise, inheritance, gift or estate taxes.  Real property taxes
also shall not include any tax or assessment expense (i) in excess of the amount
which would be payable if such tax or assessment expense were paid in
installments over the longest possible term; or (ii) imposed on land and
improvements other than the Building and/or Site.  Tenant may in good faith
contest any tax or assessment, provided that Tenant indemnifies Landlord from
any loss or liability in connection therewith and further provided that Tenant
bears the cost of any such contest including without limitation the cost of any
interest and penalties which may be assessed.

5.2  Tenant shall directly and timely pay all electrical, gas, water, garbage
and sewer costs as well as janitorial costs (including the cost of janitorial
supplies) relating to the Premises.  With respect to janitorial costs (including
the cost of janitorial supplies) tenant shall be entitled to contract with such
supplier of 
<PAGE>
 
janitorial services as Tenant may elect (subject to the approval of Landlord,
which approval shall not be unreasonably withheld or delayed), or in the
alternative, shall be entitled to internally provide janitorial services in
connection with the Premises. In all events, Tenant shall provide janitorial
services in connection with the Premises in a commercially reasonable fashion
consistent with janitorial services provided in first class commercial
buildings in the geographical area in which the Premises is located. The cost
of all janitorial supplies in connection with the Premises shall be the
responsibility of Tenant. All such janitorial costs (including the costs of
janitorial supplies) shall be paid directly by Tenant. Upon request of the
Landlord, from time to time, but no more frequently than once during each
Lease Year, Tenant shall provide to Landlord evidence reasonably satisfactory
to Landlord of the payment of such costs. In the event that such costs are not
timely paid by Tenant, Landlord shall be entitled (but not obligated), upon
ten (10) days prior notice to Tenant, to pay such costs which payment shall
promptly be reimbursed by Tenant to Landlord within twenty (20) days after
receipt of Landlord's invoice, together with interest equal to the annual rate
of the lesser of ten percent (10%) or the maximum rate allowed by law from the
date of payment to the date of receipt by Landlord.


5.3  No later than April of each calendar year following the Lease Commencement
Date during the Term of this Lease, or as soon thereafter as possible, Landlord
shall endeavor to deliver to Tenant a statement ("Estimate Statement") wherein
Landlord shall estimate the Operating Expenses for the current calendar year,
and Tenant's Percentage Share of the excess, if any, of the estimated Operating
Expenses for the current calendar year over the Operating Expenses for the Base
Year.  If Operating Expenses estimated in the Estimate Statement of the current
calendar year exceed the Operating Expenses of the Base Year then Tenant's
Percentage Share of such excess amount shall be divided into twelve (12) equal
monthly installments and Tenant shall pay to Landlord within thirty (30) days,
following the receipt of such statement, an amount equal to one (1) monthly
installment multiplied by the number of months from January in the calendar year
in which said statement is submitted to the month of such payment, both months
inclusive.  Subsequent installments shall be paid concurrently with the regular
monthly rent payments for the balance of the calendar year and shall continue
until the next calendar year's Estimate Statement is rendered.  If Landlord
determines that Tenant's Percentage Share of the excess Operating Expenses for
such current calendar year is greater than that set forth in the Estimate
Statement, then Landlord may, at any time, but not more frequently than once
during each Lease Year, deliver a revised Estimate Statement and Tenant shall
pay to Landlord, within thirty (30) days of the delivery of such revised
Estimate Statement, the difference between such revised Estimate Statement and
the original Estimate Statement for the portion of the current calendar year
which has then expired and Tenant shall pay during the balance of such current
calendar year a fraction of the balance of such difference as would fully
amortize such excess over the remaining months of the then current calendar
year.  Notwithstanding anything to the contrary set forth in this Paragraph 5.3,
or elsewhere in this Lease or the Summary, Tenant shall have no obligation to
pay Tenant's Percentage Share of the increase in Operating Expenses over the
Base Year for the first twelve full calendar (12) months following the Lease
Commencement Date.  Tenant's first obligation to pay Operating Rent shall accrue
in the thirteenth full calendar (13th) month following the Lease Commencement
Date.  Notwithstanding the designation of Base Year in the Summary, for purposes
of calculating Tenant's share of the increase in real property taxes, the
initial real property taxes for purposes of determining any increase, shall be
the real property taxes based on an assessed value of the Premises, Building and
Site which takes into account the construction of Landlord's Work and the
Tenant's Improvements.  Tenant's obligation to pay increases in real property
taxes, if any, 
<PAGE>
 
shall commence as of the thirteenth (13th) full calendar month following the
Lease Commencement Date even if such increases, if any, cannot be calculated
until subsequent to such time.

     By the first day of June of each succeeding calendar year during the Term
of this Lease, or as soon thereafter as possible (but, in any event, no later
than December 31 of such succeeding calendar year), Landlord shall endeavor to
deliver to Tenant a statement ("Actual Statement") wherein Landlord shall state
the actual Operating Expenses for the preceding calendar year.  If the Actual
Statement reveals a greater increase in Tenant's Percentage Share of Operating
Expenses in excess of the Base Year than was estimated by Landlord in the
Estimate Statement delivered as provided herein, then within thirty (30) days
following receipt of the Actual Statement by Landlord, Tenant shall pay a lump
sum equal to said total increase over the Operating Expenses for the Base Year,
less the total of the monthly installments of increases set forth on the
Estimate Statement which were paid in the previous calendar year.  If the Actual
Statement reveals that Tenant overpaid Operating Expenses for any calendar year,
any overpayment made by Tenant on the monthly installment basis provided above
shall be credited toward the next monthly rent falling due and the monthly
installment of Tenant's Percentage Share of Operating Expenses to be paid
pursuant to the then current Estimate Statement shall be adjusted to reflect
such lower expenses for the most recent calendar year, or if this Lease has been
terminated, such excess shall be credited against any amount which Tenant owes
Landlord pursuant to this Lease and, to the extent all amounts which Tenant owes
Landlord pursuant to this Lease have been paid, Landlord shall promptly pay such
excess to Tenant.  Landlord shall not be entitled to deliver an Actual Statement
more than one time per calendar year.  Any delay or failure by Landlord in
delivering any estimate or statement pursuant to this Paragraph shall not
constitute a waiver of its right to require an increase in Tenant's share of the
Operating Expenses in excess of the Base Year nor shall it relieve Tenant of its
obligations pursuant to this Paragraph, except that Tenant shall not be
obligated to make any payments based on such estimate or statement until thirty
(30) days after receipt of such estimate or statement.

5.4  Even though the Term has expired and Tenant has vacated the Premises, when
the final determination is made of Tenant's Percentage Share of Operating
Expenses for the year in which this Lease terminates, Tenant, within twenty (20)
days after receipt of Landlord's determination, shall pay any increase due over
the estimated expenses paid and conversely any overpayment made in the event
said expenses decrease shall be rebated by Landlord to Tenant, within twenty
(20) days after Landlord's determination.

5.5  Notwithstanding anything contained in this Paragraph 5, the rental payable
by Tenant each month shall in no event be less than the Monthly Basic Rent
specified in Paragraph 4 hereof.  The excess Operating Expenses to be paid by
Tenant to Landlord pursuant to the provisions of this Paragraph 5 shall
sometimes be referred to in the aggregate as the "Operating Rent".


5.6  Notwithstanding any provision to the contrary contained in this Lease,
within sixty  days after receipt by Tenant of Landlord's Operating Expenses for
any prior calendar year during the Term, Tenant or its authorized representative
shall have the right to inspect the books of Landlord upon reasonable notice and
during the business hours of Landlord at Landlord's office in the Building, or,
at Landlord's option, at such other location as Landlord reasonably may specify,
for the purpose of verifying the information contained in the statement.  Unless
Tenant asserts specific errors within sixty (60) days after 
<PAGE>
 
receipt of the statement, the statement shall be deemed correct as between
Landlord and Tenant.


6. Security Deposit.
   ----------------

6.1  As and for security for Tenant's full and faithful performance of all the
terms, covenants and conditions of this Lease to be kept and performed by
Tenant, Tenant shall deposit with Landlord (i) cash in the amount of Two Hundred
Two Thousand, Two Hundred Seventy-Five Dollars ($202,275.00) and (ii) an
unconditional, irrevocable letter of credit ("LOC") in favor of Landlord in the
sum of Seven Hundred Ninety-Seven Thousand, Seven Hundred Twenty-Five Dollars
($797,725.00) (subject to adjustment pursuant to Subparagraph 6.2) from a bank
or other financial institution and in a form reasonably acceptable to Landlord.
If at any time during the Term, any item constituting rent as provided herein,
or any other sum payable by Tenant to Landlord hereunder, shall be overdue and
unpaid, beyond applicable cure periods, then Landlord may, at the sole option of
Landlord, but without any requirement to do so, draw down or make a claim or
demand for draw against the LOC (or at the election of Landlord against the cash
portion of the security deposit) an amount equal to the overdue and unpaid
amount, together with Landlord's actual and reasonable expenses incurred in
connection with the default, and apply such sum to payment of such overdue rent
or other sum.  The LOC shall provide that any draw thereunder shall be
accompanied by a certificate of an officer of Landlord stating that Tenant is in
default under the Lease beyond the applicable notice and cure period, if any,
and that Landlord or its authorized agent is entitled to draw down on the LOC
the amount requested pursuant to the terms of this Lease.  Further in the event
of the failure of Tenant to keep and perform any term, covenant or condition of
this Lease to be kept or performed by Tenant, beyond applicable cure periods,
then, at the sole option of Landlord, and after termination of this Lease,
Landlord may draw down the entire LOC (and draw against any remaining cash
portion of the security deposit), or so much thereof as may be necessary to
compensate Landlord for any loss or damage sustained or suffered by Landlord due
to such breach on the part of Tenant. In the event that all or any portion of
the LOC is drawn down by Landlord to pay overdue rent or other sums due and
payable to Landlord by Tenant hereunder, then Tenant shall, within ten (10) days
after receipt of written demand of Landlord, promptly remit to Landlord a
sufficient amount in cash or an additional letter of credit to restore
Landlord's security to the original amount of the LOC as provided in this
Paragraph. In the event that all or any portion of the cash portion of the
security deposit is charged against by Landlord to pay overdue rent or other
sums due and payable to Landlord by Tenant hereunder, then Tenant shall, within
ten (10) days after receipt of written demand of Landlord, promptly remit to
Landlord a sufficient amount in cash to restore the cash portion of Landlord's
security deposit as drawn against by Landlord. Any failure on the part of Tenant
to restore either the cash portion of the security deposit or the LOC in
accordance with the provisions immediately above within ten (10) days following
the date on which demand for restoration is deemed given hereunder, shall
constitute a default by Tenant pursuant to this Lease. In the event Landlord
transfers the LOC and the cash portion of the security deposit to any successor
in interest of Landlord to title of the Site and Building, then, in such event,
Landlord shall be discharged from any further obligation or liability with
respect to the LOC and the cash portion of the security deposit. Tenant waives
the provisions of California Civil Code Section 1950.7 and all other provisions
of law now in force or that become in force after the date of execution of this
Lease that provide that Landlord may claim from a security deposit only those
sums reasonably necessary to remedy defaults in the payment of rent, to repair
damages caused by Tenant, or to clean the Premises. Landlord and Tenant agree
that Landlord may, in addition, claim those sums reasonably necessary to
compensate
<PAGE>
 
Landlord for any out-of-pocket (but not consequential) loss or damage caused by
any act or omission of Tenant or Tenant's officers, agents, employees,
independent contractors or invitees. Landlord's obligations with respect to the
cash portion of the security deposit are those of a debtor and not of a trustee,
and Landlord is entitled to commingle the cash portion of the security deposit
with Landlord's general funds. Landlord shall not be required to pay Tenant
interest on any portion of the security deposit including without limitation the
cash portion of the security deposit.

     The cash portion of the security deposit shall be delivered by Tenant to
Landlord within five (5) days following execution and delivery by Landlord and
Tenant of this Lease.  The LOC shall be delivered by Tenant to Landlord within
ten (10) days after execution and delivery of this Lease by Landlord and Tenant.

6.2  The LOC shall be subject to adjustment under the following circumstances:

(a)     Provided that Tenant completely and faithfully performs all terms,
conditions and obligations imposed upon Tenant by this Lease for the first nine
full calendar (9) months of the Term, and provided that Tenant is not then in
default, beyond any applicable cure period, of this Lease, the LOC may be
reduced by ten percent (10%) of its original amount at the conclusion of said
nine (9) month period.  Thereafter, on each subsequent anniversary date of the
first reduction, and provided Tenant has not been in default of this Lease since
the prior reduction in the LOC, the LOC may be further reduced by ten percent
(10%) of the outstanding amount of the LOC.  Notwithstanding any provision to
the contrary of this Lease including, without limitation, the provisions of this
Paragraph 6.2, in no event shall the security deposit to be given by Tenant,
pursuant to the provisions of Paragraph 6 be reduced to an amount less than a
cash deposit in the amount of Two Hundred and Two Thousand, Two Hundred and
Seventy-five Dollars ($202,275.00),  Such minimum cash deposit shall be subject
to return to Tenant upon the expiration or earlier termination of this Lease
only in accordance with the provisions of Paragraph 6.5 below.

(b)     If, on the tenth (10) month anniversary of the Lease Commencement
Date, or at any time thereafter, Tenant provides Landlord with satisfactory
evidence (such as audited financial statements) that Tenant's earnings before
income taxes, depreciation and amortization (EBITDA) reflect a profit for the
immediately preceding three (3) consecutive calendar quarters, and Tenant's
net worth is no less than Seventy-Five Million Dollars ($75,000,000.00), then
the LOC may be reduced to one month's Monthly Basic Rent. Thereafter, the LOC
shall be increased (i) to two (2) month's Monthly Basic Rent if Tenant's net
worth as determined in accordance with generally accepted accounting
principles falls below Seventy-Five Million Dollars ($75,000,000.00), (ii) to
four (4) month's Monthly Basic Rent if Tenant's net worth falls below Fifty
Million Dollars ($50,000,000.00), and (iii) to six (6) month's Monthly Basic
Rent if Tenant's net worth falls below Thirty Million Dollars
($30,000,000.00). Further, in the event that the financial statements of
Tenant at any time reflect a loss for two or more consecutive calendar
quarters on the basis of EBITDA, then the amount of the LOC otherwise then in
effect shall be increased by an amount equal to one month of Monthly Basic
Rent. All multiples of Monthly Basic Rent shall be calculated at a rental rate
of $32.50 per square foot of the Premises. The provisions of this Subparagraph
6.2(b) shall control in the event of a conflict with Subparagraph 6.2 (a).
Notwithstanding any provisions to the contrary contained in this Paragraph
6.2, if Tenant's net worth, after falling below any of the variables described
above in this Paragraph 6.2(b), subsequently rises to a higher net worth
threshold and
<PAGE>
 
remains at such higher threshold for three consecutive months, at the end of
such three month period Tenant shall have the right to replace the LOC in the
higher amount with an LOC for the lower amount provided for with respect to
the higher net worth threshold as described above in this Paragraph 6.2(b)
that Tenant has maintained for the preceding three month period subject,
however, to subsequent increase in the amount of the LOC should Tenant's net
worth again fall below such higher threshold amount. Tenant shall from time to
time promptly provide to Landlord for each calendar quarter during the Term
hereof a copy of Tenant's financial statement (audited if available) provided
that Tenant shall not be obligated to provide Landlord with a copy of Tenant's
financial statement more often than once per calendar quarter.

6.3  If, after any default by Tenant beyond applicable cure periods and a
termination of this Lease by Landlord as set forth in Paragraph 6.1 above and
Landlord has drawn down the entire LOC, any proceeds of the LOC in excess of
the sum equal to the amount necessary to compensate Landlord for any loss or
damage sustained or suffered by Landlord due to Tenant's default, together
with Landlord's actual and reasonable expenses incurred in connection
therewith, shall be held in a separate, interest-bearing account ("Account")
in Landlord's name at such national bank as Landlord reasonably selects
("Bank"). Tenant shall have no rights to the money in the Account, except for
(i) the return rights specified below, and (ii) the right to receive interest
on the Account, as specified herein. Landlord agrees to place on the signature
card for the Account the following language "[name of Landlord] is holding the
funds in the Account in accordance with a Lease dated [date of Lease] between
[name of Landlord] and USWeb Corporation. The rights of [name of Landlord] and
USWeb Corporation in and to the funds are subject to the terms of such Lease."
Within ten (10) business days after Landlord signs the signature card (or any
replacement signature card) on the Account, Landlord agrees to provide Tenant
with a copy of the signature card for the Account. Landlord agrees to request
the Bank to pay interest on the Account directly to Tenant on a quarterly
basis, and to report to the appropriate taxing authorities that such interest
has been paid to Tenant; provided, however, that if, despite Landlord's
request, the Bank will not or cannot pay the interest directly to Tenant, the
(x) the Bank shall pay interest on the Account directly to Landlord, in which
case, within ten (10) business days after Landlord receives such payment of
interest, Landlord shall pay to Tenant the interest Landlord receives from the
Bank on the Account, and (y) Landlord shall have the right to report to the
appropriate taxing authorities that such income is the income of Tenant.
Tenant represents to Landlord that Tenant's Federal Taxpayer Identification
Number is 87-0551650. If the proceeds of the LOC are placed in a fixed term
instrument, such as a certificate of deposit, then Landlord shall not be
liable for any prepayment penalty if Landlord uses the Account, or a portion
thereof, in accordance with the provisions of this Paragraph 6.


6.4  Notwithstanding anything contained in this Paragraph 6 to the contrary, if
Landlord draws on the LOC an amount in excess of the amount necessary to
compensate Landlord in full for any loss or damage sustained or suffered by
Landlord due to the default of Tenant, then Tenant shall have the right, upon
ten (10) days' prior written notice to Landlord, to obtain a refund from
Landlord of any excess proceeds of the LOC which Landlord has drawn upon, any
such refund being conditioned upon Tenant simultaneously delivering to Landlord
a new replacement LOC in the amount then required, and otherwise meeting the
requirements contained in this Paragraph 6.


6.5  Upon the expiration or earlier termination of this Lease, Landlord shall
return to Tenant so much 
<PAGE>
 
of the LOC (and the cash portion of the security deposit) as has not been
applied or entitled to be held by Landlord to be applied to cure any and all
defaults by Tenant occurring prior to the expiration or earlier termination of
this Lease and any default by Tenant pursuant to the provisions of Paragraph
13.1(f) below.


7. Use.
   ---

7.1  Tenant shall use the Premises for general office purposes and purposes
incident thereto and shall not use or permit the Premises to be used for any
other purpose without the prior written consent of Landlord, which consent may
be granted or withheld in Landlord's sole discretion.  Tenant shall not use or
occupy the Premises in violation of any recorded covenants, conditions and
restrictions affecting the Site or of any law or of the Certificate of Occupancy
issued for the Building, and shall upon five (5) days' written notice from
Landlord, discontinue any use of the Premises which is declared by any
governmental authority having jurisdiction to be a violation of any recorded
covenants, conditions and restrictions affecting the Site or of any law or of
said Certificate of Occupancy.  Subject to the provision of Paragraph 54.2,
Tenant shall not install any radio or television antenna, loudspeaker or other
device on the roof or exterior walls of the Building.  Tenant shall not
interfere with radio or television broadcasting or reception from or in the
Building or elsewhere.  Tenant shall comply with any direction of any
governmental authority having jurisdiction which shall, by reason of the nature
of Tenant's specific use or alteration of the Premises, impose any duty upon
Tenant or Landlord with respect to the Premises or with respect to the use or
occupation thereof.  Tenant shall not do or permit to be done anything which
will invalidate or increase the cost of any fire, extended coverage or any other
insurance policy covering the Building and/or property located therein and shall
comply with all rules, orders, regulations and requirements of the Pacific Fire
Rating Bureau or any other organization performing a similar function.  Tenant
shall within twenty (20) days after receipt of demand reimburse Landlord as
additional rent for any additional premium charged for such policy by reason of
Tenant's failure to comply with the provisions of this Paragraph 7.  Tenant
shall not do or permit anything to be done in or about the Premises which will
in any way obstruct or interfere with the rights of other tenants or occupants
of the Building, or injure them, or use or allow the Premises to be used for any
unlawful purpose, nor shall Tenant cause, maintain or permit any nuisance in, on
or about the Premises.  Tenant shall not commit or suffer to be committed any
waste in or upon the Premises and shall keep the Premises in first-class repair
and appearance.  Tenant shall not place a load upon the Premises exceeding the
average pounds of live load per square foot of floor area specified for the
Building by Landlord's Architect, with the partitions to be considered a part of
the live load.  Landlord reserves the right to prescribe the weight and position
of all safes, files and heavy equipment which Tenant desires to place in the
Premises so as to distribute properly the weight thereof.  Tenant's business
machines and mechanical equipment which cause vibration or noise that may be
transmitted to the Building structure or to any other space in the Building
shall be so installed, maintained and used by Tenant as to eliminate such
vibration or noise.  Tenant shall be responsible for all structural engineering
required to accommodate the structural load.  Tenant shall fasten all files,
bookcases and like furnishings to walls in a manner to prevent tipping over in
the event of earth movements.  Landlord shall not be responsible for any damage
or liability for such events.

7.2  Except for the normal and proper use and storage of  typical cleaning
fluids and solutions, and office equipment supplies (such as copier toner), in
amounts commensurate with Tenant's use and occupancy of the Premises, Tenant
shall not use, introduce to the Premises, generate, manufacture, 
<PAGE>
 
produce, store, release, discharge or dispose of, on, under or about the
Premises or transport to or from the Premises any Hazardous Material (as
defined below) or allow its employees, agents, contractors, invitees or any
other person or entity to do so. Tenant warrants that it shall not make any
use of the Premises which may cause contamination of the soil, the subsoil or
ground water. Tenant shall keep and maintain the Premises in compliance with,
and shall not cause or permit the Premises to be in violation of any and all
federal, state or local laws, ordinances, rules or regulations pertaining to
health, industrial hygiene or the environmental conditions on, under or about
the Premises. Tenant shall give immediate written notice to Landlord of (i)
any action, proceeding or inquiry by any governmental authority or any third
party with respect to the presence of any Hazardous Material on the Premises
or the migration thereof from or to other property or (ii) any spill, release
or discharge of Hazardous Materials that occurs with respect to the Premises
or Tenant's operations.

(a)     Tenant shall indemnify and hold harmless Landlord, its directors,
officers, employees, agents, successors and assigns (collectively "Landlord")
from and against any and all claims arising from Tenant's use of the Premises
in violation of this paragraph. The indemnity shall include all costs, fines,
penalties, judgments, losses, reasonable attorney's fees, expenses and
liabilities incurred by Landlord for any such claim or any action or
proceeding brought thereon including, without limitation, (a) all foreseeable
consequential damages including without limitation loss of rental income and
diminution in property value; and (b) the costs of any cleanup, detoxification
or other ameliorative work of any kind or nature required by any governmental
agency having jurisdiction thereof or Landlord. This indemnity shall survive
the expiration or termination of this Lease. In any action or proceeding
brought against Landlord by reason of any such claim, upon notice from
Landlord if Landlord does not elect to retain separate counsel, Tenant shall
defend the same at Tenant's expense by counsel reasonably satisfactory to
Landlord.

(b)     Landlord shall indemnify and hold harmless Tenant, its directors,
officers, employees, agents, successors and assigns (collectively, "Tenant")
from and against any and all claims arising from or relating to Hazardous
Materials actually existing and present at the Building or the Site or within
the Premises as of the Lease Commencement Date. The indemnity shall include
all costs, fines, penalties, judgments, losses, reasonable attorney's fees,
expenses and liabilities incurred by Tenant for any such claim or any action
or proceeding brought thereon including, without limitation, (a) all
foreseeable consequential damages; and (b) the cost of any clean up,
detoxification or other ameliorative work of any kind or nature required by
any governmental agency having jurisdiction thereof. This indemnity shall
survive the expiration or termination of this Lease. Any action or proceeding
brought against Tenant by reason of any such claim, upon notice from Tenant,
if Tenant does not elect to retain separate counsel, Landlord shall defend the
same at Landlord's expense by counsel reasonably satisfactory to Tenant.

(c)     As used herein, the term "Hazardous Material" shall mean any substance
or material which has been determined by any state, federal or local
governmental authority to be capable of posing a risk of injury to health,
safety or property, including all of those materials and substances designated
as hazardous or toxic by the city in which the Premises are located, the U.S.
Environmental Protection Agency, the Consumer Product Safety Commission, the
Food and Drug Administration, the California Water Resources Control Board,
the Regional Water Quality Control Board, San Francisco Bay Region, the
California Air Resources Board, CAL/OSHA Standards Board, Division of
Occupational Safety and Health, the California Department of Food and
Agriculture, the California Department of Health Services, 
<PAGE>
 
and any federal agencies that have overlapping jurisdiction with such
California agencies, or any other governmental agency now or hereafter
authorized to regulate materials and substances in the environment. Without
limiting the generality of the foregoing, the term "Hazardous Material" shall
included all of those materials and substances defined as "hazardous
materials" or "hazardous waste" in Sections 66680 through 66685 of Title 22 of
the California Administrative Code, Division 4, Chapter 30, as the same shall
be amended from time to time, petroleum, petroleum-related substances and the
by-products, fractions, constituents and sub-constituents of petroleum or
petroleum-related substances, asbestos, and any other materials requiring
remediation now or in the future under federal, state or local statutes,
ordinances, regulations or policies.


8. Payments and Notices.  All rents and other sums payable by Tenant to 
   --------------------
Landlord hereunder shall be paid to Landlord by check at the address
designated by Landlord in the Summary or at such other places as Landlord may
hereafter designate in writing. Any notice required or permitted to be given
hereunder must be in writing and may be given by personal delivery, mail, or
by recognized overnight courier. If notice is given by personal delivery, such
notice shall be deemed to be given upon delivery, if notice is given by
registered or certified mail addressed to Tenant at the address designated in
the Summary or to Landlord at both of the addresses designated in the Summary,
then such notice shall be deemed given three (3) business days following
deposit in the U.S. mail, postage prepaid, addressed to Tenant as designated
in the Summary or to Landlord at both of the addresses designated in the
Summary and if given by overnight courier shall be deemed given one (1)
business day following delivery to the courier, charges prepaid, addressed as
stated above. Either party may by written notice to the other specify a
different address for notice purposes. If more than one person or entity
constitutes the "Tenant" under this Lease, service of any notice upon any one
of said persons or entities shall be deemed as service upon all of said
persons or entities.


9. Brokers.  The parties recognize that the brokers who negotiated this Lease 
   -------
are the brokers whose names are stated in the Summary, and agree that Landlord
shall be solely responsible for the payment of brokerage commissions to said
brokers, and that Tenant shall have no responsibility therefor. As part of the
consideration for the granting of this Lease, Tenant represents and warrants
to Landlord that to Tenant's knowledge no other broker, agent or finder
negotiated or was instrumental in negotiating or consummating this Lease and
that Tenant knows of no other real estate broker, agent or finder who is, or
might be, entitled to a commission or compensation in connection with this
Lease. Any broker, agent or finder of Tenant whom Tenant has failed to
disclose herein shall be paid by Tenant. Tenant shall hold Landlord harmless
from all damages and indemnify Landlord for all said damages paid or incurred
by Landlord resulting from any claims that may be asserted against Landlord by
any broker, agent or finder who has, or has claimed to have, rendered services
to Tenant undisclosed by Tenant herein. Landlord shall hold Tenant harmless
from all damages and indemnify Tenant for all said damages paid or incurred by
Tenant resulting from any claims that may be asserted against Tenant by any
broker, agent or finder who has, or has claimed to have, rendered services to
Landlord undisclosed by Landlord herein.


10.Holding Over.  If Tenant remains in possession of the Premises after 
   ------------
expiration or earlier termination of this Lease with Landlord's express
consent, Tenant's occupancy shall be a month to month tenancy at a rent agreed
upon by Landlord and Tenant but, in no event less than the aggregate of the
Monthly Basic Rent, Parking Lot Rent and Tenant's Percentage Share of the
Operating Costs payable under this Lease 
<PAGE>
 
during the last full month before the date of expiration or earlier
termination. The month to month tenancy shall be on the terms and conditions
of this Lease except as provided in the preceding sentence and the Lease
clauses concerning extension rights. If Tenant holds over after the expiration
or earlier termination of the Term hereof without the express written consent
of Landlord, Tenant shall become a tenant at sufferance only, at a rental rate
equal to one hundred fifty percent (150%) of the Monthly Basic Rent and
Parking Lot Rent which would be applicable to the Premises upon the date of
such expiration (subject to adjustment as provided herein and prorated on a
daily basis) for the first sixty (60) days of such holdover, and two hundred
percent (200%) of such aggregate amount thereafter during the pendency of such
holdover, and otherwise subject to the terms, covenants and conditions herein
specified, so far as applicable including, without limitation, the obligation
to pay increased Operating Expenses as provided in Paragraph 5. Acceptance by
Landlord of rent after such expiration or earlier termination shall not
constitute a consent to a holdover hereunder or result in a renewal. The
foregoing provisions of this Paragraph 10 are in addition to and do not affect
Landlord's right of re-entry or any rights of Landlord hereunder or as
otherwise provided by law. If Tenant fails to surrender the Premises upon the
expiration of this Lease despite demand to do so by Landlord, Tenant shall
indemnify and hold Landlord harmless from all loss or liability arising out of
such failure, including without limitation, any claim made by any succeeding
tenant founded on or resulting from such failure to surrender. No provision of
this Paragraph 10 shall be construed as implied consent by Landlord to any
holding over by Tenant. Landlord expressly reserves the right to require
Tenant to surrender possession of the Premises to Landlord as provided in this
Lease upon expiration or other termination of this Lease. The provisions of
this Paragraph 10 shall not be considered to limit or constitute a waiver of
any other rights or remedies of Landlord provided in this Lease or at law.


11.Taxes on Tenant's Property.  Tenant shall be liable for and shall pay 
   --------------------------
before delinquency, taxes levied against any personal property or trade
fixtures placed by Tenant in or about the Premises. If any such taxes on
Tenant's personal property or trade fixtures are levied against Landlord or
Landlord's property or if the assessed value of the Premises is increased by
the inclusion therein of a value placed upon such personal property or trade
fixtures of Tenant and if Landlord, after written notice to Tenant, pays the
taxes based upon such increased assessments, which Landlord shall have the
right to do regardless of the validity thereof, but only under proper protest
if requested by Tenant, Tenant shall within ten (10) days after receipt of
demand repay to Landlord the taxes levied against Landlord, or the proportion
of such taxes resulting from such increase in the assessment; provided that in
any such event, at Tenant's sole cost and expense, Tenant shall have the
right, in the name of Landlord and with Landlord's full cooperation, to bring
suit in any court of competent jurisdiction to recover the amount of any such
taxes so paid under protest, any amount so recovered to belong to Tenant.


12.Condition of Premises.  Other than with respect to the completion of 
   --------------------- 
Landlord's construction obligations set forth in the Work Letter, which shall
be done in a good and workmanlike manner in accordance with all applicable law
(including, without limitation, the Americans With Disabilities Act of 1990)
and in accordance with the provisions of the Work Letter, using materials and
equipment of good quality, Tenant acknowledges that neither Landlord nor any
agent of Landlord has made any representation or warranty of any kind
whatsoever with respect to the Premises or the Building or with respect to the
suitability of either for the conduct of Tenant's business. The acceptance of
possession of the Premises by Tenant after receipt of the Notice, without
objection within the time prescribed for such 
<PAGE>
 
objection, shall conclusively establish that the Premises and the Building
were at such time in satisfactory condition. Tenant acknowledges and agrees
that Tenant is relying solely upon Tenant's own inspection of the Premises,
and Tenant is not relying on any representation or warranty from the Landlord
regarding the Premises or the Building, except as specifically set forth in
this Lease or the Work Letter, including, without limitation, any
representation or warranty as to the physical condition, design or layout of
the Premises. Notwithstanding the foregoing; as of the Lease Commencement
Date, the heating, ventilating and air conditioning system, and the
electrical, plumbing, sewer, life safety and, if applicable, security systems
(collectively, "Building Systems") serving the Premises shall be in good
working order and repair. In connection with delivery of possession of the
Premises to Tenant with Landlord's Work and the Tenant's Improvements having
been substantially completed, Tenant, together with Tenant's Architect and a
representative of Landlord and Landlord's Architect, shall conduct a walk
through of the Premises and prepare a punch list setting forth a description
of any and all of Landlord's Work and/or Tenant's Improvements remaining to be
completed or defective and requiring repair or replacement as reasonably
determined by Tenant's Architect and Landlord's Architect. Landlord shall,
following the preparation of such punch list, diligently pursue completion or
repair of the punch list items and upon completing or repairing all such punch
list items, Landlord shall be considered to have fulfilled its obligations in
connection with construction of both the Landlord's Work and the Tenant's
Improvements. Landlord shall for a period of thirty (30) days following
delivery of possession of the Premises to Tenant, perform any repairs required
in connection with the Building Systems so as to maintain such systems in good
working order and repair, provided, however, that Landlord shall have no
obligation to make any repairs in connection with any portion of the Building
Systems damaged by Tenant or any of Tenant's contractors, employees or agents.


13.Alterations.
   -----------

13.1 Tenant may, at any time and from time to time during the Term of this
Lease, at its sole cost and expense, make alterations, additions, installations,
substitutions, improvements and decorations (hereinafter collectively called
"Changes" and individually, a "Change") in and to the Premises, excluding
structural changes, on the following conditions, and providing such Changes will
not result in a violation of or require a change in the Certificate of Occupancy
applicable to the Premises:

(a)     The outside appearance, character or use of the Building shall not be
affected, and no Changes shall weaken or impair the structural strength or, in
the reasonable opinion of Landlord, lessen the value of the Building or create
the potential for unusual expenses to be incurred upon the removal of Changes
and the restoration of the Premises upon the termination of this Lease.

(b)     No part of the Building outside of the Premises shall be physically
affected.
(c)     The proper functioning of any of the mechanical, electrical, sanitary
and other service systems or installations of the Building ("Service
Facilities") shall not be adversely affected and there shall be no
construction which might interfere with Landlord's free access to the Service
Facilities or interfere with the moving of Landlord's equipment to or from the
enclosures containing the Service Facilities.
(d)     In performing the work involved in making such Changes, Tenant shall be
bound by and 
<PAGE>
 
observe all of the conditions and covenants contained in this Paragraph 13.
(e)     All work shall be done at such times and in such manner as Landlord from
time to time may reasonably designate.
(f)     At the date upon which the Term of this Lease shall end, or the date
of any earlier termination of this Lease, Tenant shall remove all Changes with
respect to which Landlord has given notice to Tenant requiring such removal as
provided in Paragraph 13.2 below and restore or repair the Premises in
accordance with the direction of Landlord as described in Paragraph 13.2
below. Such removal and restoration or repair shall be made not later than the
date of expiration of this Lease or thirty (30) days following any earlier
termination of this Lease. If Tenant fails to complete the removal and
restoration or repair, as the case may be, before the expiration of the Term,
or in the case of any earlier termination of this Lease, within thirty (30)
days following the occurrence of such termination, Landlord may complete the
removal and restoration or repair and charge the cost of such to Tenant. At
the expiration or earlier termination of this Lease, Tenant shall, in
addition, at the option of Landlord, be required to remove and restore any
Change (including a Minor Change, as defined below) with respect to which
Tenant has failed to give notice to Landlord in accordance with the provisions
of Paragraph 13.2 below. Any such removal and restoration by Tenant shall be
made within thirty (30) days following the request by Landlord (which request
by Landlord in the case of expiration of this Lease, shall not be given later
than thirty (30) days prior to such expiration and, in the case of earlier
termination of this Lease, shall not be given later than the date of such
earlier termination) and Landlord may complete the removal and restoration of
any such Change and charge the cost to Tenant in the event that Tenant fails
to timely complete such removal and restoration.

13.2 Before proceeding with any Change (exclusive only of changes to items
constituting Tenant's personal property and non-structural Changes not costing
in the aggregate more than Twenty-five Thousand Dollars ($25,000) per work of
improvement and not requiring any building permit or other like permit from any
applicable governmental agency), Tenant shall submit to Landlord plans and
specifications for the work to be done, which shall in all cases require
Landlord's prior written approval which shall not be unreasonably withheld or
delayed.  In connection with any nonstructural changes not costing in the
aggregate, more than Twenty-five Thousand Dollars  ($25,000) per work of
improvement and not requiring any building permit or like permit from any
applicable governmental agency ("Minor Change"), Tenant shall deliver to
Landlord at least ten (10) days prior to  commencement of  such Minor Change, a
general description of the proposed Change including a copy of any plans and
specifications available.  Landlord's consent shall not be required in
connection with any proposed Minor Change although construction of any such
Minor Change by Tenant shall otherwise be performed in accordance with the
provisions of this Paragraph 13.  At the time Tenant requests the consent of
Landlord to a proposed Change (other than a Minor Change) Landlord, in
connection with granting any such consent shall advise Tenant as to whether
Landlord will require Tenant upon the expiration of this Lease or any earlier
termination of this Lease to remove any such Change and, in the event that
Landlord elects to require such removal, whether Landlord will require Tenant to
(i) restore the Premises to its condition prior to the making of such Change or,
(ii) merely to remove the Change and repair any damages resulting from such
removal.  In connection with any Minor Change of which Landlord receives notice
from Tenant, Landlord shall advise Tenant as to whether Landlord will require
removal of such Change at the 
<PAGE>
 
expiration or earlier termination of this Lease and in connection with any
required removal, as to whether Landlord will require restoration or merely
repair as described above. In connection with any Change requiring Landlord's
approval, Landlord may confer with consultants in connection with the review
of the plans and specifications. If Landlord or such consultant(s) shall
disapprove of any of the Tenant's plans Tenant shall be advised of the reasons
of such disapproval. In any event, Tenant agrees to pay to Landlord, as
additional rent, the reasonable cost of such consultation and review (but not
in excess of $1,000 per request) within twenty (20) days after receipt of
invoices either from Landlord or such consultant(s). Any Change for which
approval has been received shall be performed strictly in accordance with the
approved plans and specifications, and no material amendments or additions to
such plans and specifications shall be made without the prior written consent
of Landlord which shall not be unreasonably withheld or delayed and Minor
Changes shall generally be performed in accordance with the notice given by
Tenant to Landlord.

13.3 If the proposed Change requires approval by or notice to the lessor of a
superior lease or the holder of a mortgage, no Change shall be proceeded with
until such approval has been received, or such notice has been given, as the
case may be, and all applicable conditions and provisions of said superior lease
or mortgage with respect to the proposed Change or alteration have been met or
complied with at Tenant's expense; and Landlord, if it approves the Change, will
promptly request such approval or give such notice, as the case may be.

13.4 Tenant shall submit to Landlord the name and address of each contractor
intended to be used by Tenant in connection with construction of Changes and
Landlord's approval thereof shall not be unreasonably withheld or delayed.  No
contractor which is reasonably unacceptable to Landlord shall be engaged by
Tenant.  All costs and expenses incurred in Changes shall be timely paid by
Tenant after each billing therefor.  If Landlord approves the construction of
specific interior improvements in the Premises by contractors or mechanics
selected by Tenant and approved by Landlord, then Tenant's contractors shall
obtain on behalf of Tenant and at Tenant's sole cost and expense, (i) all
necessary governmental permits and certificates for the commencement and
prosecution of Tenant's Changes and for final approval thereof upon completion,
and (ii) at Landlord's request, a completion and lien indemnity bond, or other
surety, reasonably satisfactory to Landlord, for the Changes.  In the event
Tenant shall request any changes in the work to be performed after the
submission of the plans referred to in this Paragraph 13, such additional
changes shall be subject to the same approvals and notices as the changes
initially submitted by Tenant.

13.5 All Changes and the performance thereof shall at all times comply with (i)
all laws, rules, orders, ordinances, directions, regulations and requirements of
all governmental authorities, agencies, offices, departments, bureaus and boards
having jurisdiction thereof, (ii) all rules, orders, directions, regulations and
requirements of the Pacific Fire Rating Bureau, or of any similar insurance body
or bodies, and (iii) all reasonable rules and regulations of Landlord, and
Tenant shall cause Changes to be performed in compliance therewith and in good
and first class workmanlike manner, using materials and equipment at least equal
in quality and class to the existing improvements and  installations of the
Building. Changes shall be performed in such manner as not to delay or impose 
any additional expense upon Landlord in construction, maintenance or operation 
of the Building, and shall be performed by contractors or mechanics approved by
Landlord and submitted to Tenant pursuant to this Paragraph, who shall
coordinate their work in cooperation with any other work being performed with
respect to the Building. 
<PAGE>
 
Throughout the performance of Changes, Tenant, at its expense, shall carry, or
cause to be carried, workmen's compensation insurance in statutory limits, and
general liability insurance for any occurrence in or about the Building, of
which Landlord and its managing agent shall be named as parties insured, in
such limits as Landlord may reasonably prescribe, with insurers reasonably
satisfactory to Landlord all in compliance with Subparagraph 20.2.
Notwithstanding any provision of this Lease to the contrary, in no event shall
Landlord be required to undertake any alteration or any improvements of any
kind whatsoever in connection with the Premises or the Building as a result of
or in connection with any Changes being made by Tenant and specifically, but
without limitation, Landlord shall not be required to make any improvements or
alteration of any kind whatsoever in order to comply with any applicable laws,
orders, ordinances, regulations or building codes which may be required in
connection with Changes being made by Tenant.

13.6 Tenant further covenants and agrees that any mechanic's lien filed against
the Premises or against the Building for work claimed to have been done for, or
materials claimed to have been furnished to Tenant, will be discharged by
Tenant, by bond or otherwise, within twenty (20) days after the receipt of
notice of filing thereof, at the cost and expense of Tenant.  All alterations,
decorations, additions or improvements upon the Premises, made by either party,
including (without limiting the generality of the foregoing) all wallcovering,
built-in cabinet work, paneling and the like, shall, unless Landlord elects
otherwise, at the time set forth in Paragraph 13.1(f) above, become the property
of Landlord, and shall remain upon, and be surrendered with the Premises, as a
part thereof, at the end of the Term hereof.  Notwithstanding any provision to
the contrary contained in this Paragraph 13.6, Tenant shall not be required to
remove or restore any Changes which Landlord agreed in accordance with the
provisions of Subparagraph 13.1(f) need not be removed or restored.  In no event
shall Tenant be obligated to remove the Landlord's Work or the Tenant's
Improvements upon the expiration or earlier termination of this Lease.

13.7 All articles of personal property and all business and trade fixtures,
machinery and equipment, furniture and movable partitions owned by Tenant or
installed by Tenant at its expense in the Premises shall be and remain the
property of Tenant and may be removed by Tenant at any time during the Term
provided Tenant is not in default hereunder, and provided that Tenant shall
repair any damage caused by such removal.  If Tenant shall fail to remove all of
its effects from said Premises upon termination of this Lease for any cause
whatsoever, Landlord may, at its option, remove the same in any manner that
Landlord shall choose, and store said effects without liability to Tenant for
loss thereof, and Tenant agrees to pay Landlord within ten (10) days after
receipt of demand any and all expenses incurred in such removal, including court
costs and reasonable attorneys' fees and storage charges on such effects for any
length of time that the same shall be in Landlord's possession or Landlord may,
at its option, without notice, sell said effects, or any of the same, at private
sale and without legal process, for such price as Landlord may obtain and apply
the proceeds of such sale against any amounts due under this Lease from Tenant
to Landlord and against the expense incident to the removal and sale of said
effects.

13.8 Subject to Landlord's agreement to minimize any disturbance of Tenant's use
of the Premises, Landlord reserves the right at any time and from time to time
without the same constituting an actual or constructive eviction and without
incurring any liability to Tenant therefor or otherwise affecting Tenant's
obligations under this Lease, to make such changes, alterations, additions,
improvements, repairs or 
<PAGE>
 
replacements in or to the Site or the Building (including the Premises if
required so to do by any law or regulation) and the fixtures and equipment
thereof, as well as in or to the street entrances, halls, passages and
stairways thereof, on ninety (90) days advance written notice to Tenant,
and/or to change the name by which the Building is commonly known, as Landlord
may deem necessary or desirable. Nothing contained in this Paragraph 13, shall
be deemed to relieve Tenant of any duty, obligation or liability of Tenant
with respect to making any repair, replacement or improvement or complying
with any law, order or requirement of any government or other authority and
nothing contained in this Paragraph 13, shall be deemed or construed to impose
upon Landlord any obligation, responsibility or liability whatsoever, for the
care, supervision or repair of the Building or any part thereof other than as
otherwise provided in this Lease. Landlord's exercise of the foregoing rights
shall not materially increase Tenant's obligations nor diminish Tenant's
rights under this Lease, or interfere with Tenant's parking rights.

13.9 The construction of the improvements to the Premises to be constructed
pursuant to the provisions of the Work Letter attached to this Lease as Exhibit
E shall be governed by the terms of such Work Letter and not by the provisions
of this Paragraph 13.


14.Repairs.
   ------- 

14.1 Subject to the provisions of Paragraph 12, by entry hereunder, Tenant
accepts the Premises as being in good and sanitary order, condition and repair.
Tenant shall, when and if needed, at Tenant's sole cost and expense, maintain
and make all repairs to the Premises and every part thereof, to keep, maintain
and preserve the Premises in first class condition, excepting ordinary wear and
tear, casualties, condemnation and acts of God.  Any such maintenance and
repairs shall be performed by Landlord's contractor, or a contractor or
contractors reasonably approved in advance in writing by Landlord.  All costs
and expenses incurred in such maintenance and repair shall be paid by Tenant
within twenty (20) days after receipt of billing by Landlord or such contractor
or contractors.  Tenant shall upon the expiration or sooner termination of the
Term hereof surrender the Premises to Landlord in the same condition as when
received, reasonable wear and tear, casualties, condemnation, Hazardous
Materials not existing, released or disbursed by Tenant or any of its employees,
agents, contractors or invitees and acts of God and Changes not required to be
removed excepted.  Landlord shall have no obligation to alter, remodel, improve,
repair, decorate or paint the Premises or any part thereof and the parties
hereto affirm that Landlord has made no representations to Tenant respecting the
condition of the Premises or the Building except as specifically herein set
forth or in the Tenant's Work Letter.  Notwithstanding anything set forth above
in this Paragraph to the contrary, Tenant shall have no obligation to install,
maintain, repair or replace any of the structural elements or systems of the
Building (including, without limitation, the Building Systems, as defined
above), unless such work is required due to Tenant's specific use or misuse of
the Premises.  Notwithstanding any provision to the contrary contained in this
Lease, as part of its maintenance and repair obligations, Tenant shall not be
required to construct or pay the cost of (i) complying with any laws existing as
of the Commencement Date, including without limitation, all Hazardous Materials
Laws (as defined below) regarding the presence of Hazardous Materials, unless
the same are stored, used or disposed of by Tenant, its agents, invitees or
employees on, in, under or about the Premises; or (ii) the correction of any
condition existing on the Premises as of the Commencement Date; or (iii) the
correction of any latent or structural defect in the Premises during the Term,
as it may be extended.
<PAGE>
 
14.2 Anything contained in Subparagraph 14.1 above to the contrary
notwithstanding, Landlord shall repair and maintain the structural portions of
the Building, including the basic plumbing, heating, ventilating, air
conditioning and electrical systems installed or furnished by Landlord, unless
such maintenance and repairs are caused in part or in whole by the act, neglect,
fault of or omission of any duty by Tenant, its agents, servants, employees or
invitees, in which case Tenant shall pay to Landlord as additional rent, the
reasonable cost of such maintenance and repairs.  Landlord shall not be liable
for any failure to make any such repairs, or to perform any maintenance unless
such failure shall persist for an unreasonable time after written notice of the
need of such repairs or maintenance is given by Tenant to Landlord.  Except as
provided in Paragraph 21 hereof there shall be no abatement of rent and no
liability of Landlord by reason of any injury to or interference with Tenant's
business arising from the making of any repairs, alterations or improvements in
or to any portion of the Building or the Premises or in or to fixtures,
appurtenances and equipment therein.  Tenant hereby waives the provisions of
California Civil Code Sections 1932(1), 1941 and 1942 and of any similar law,
statute or ordinance now or hereafter in effect.  Notwithstanding anything to
the contrary contained in this Paragraph 14, Tenant shall maintain and repair at
its sole cost and expense, and with maintenance contractors approved by
Landlord, all non-base building facilities, including lavatory, shower, toilet,
washbasin and kitchen facilities and heating and air conditioning systems,
including all plumbing connected to said facilities or systems installed by
Tenant or on behalf of Tenant (including, without limitation, the Tenant's
Improvements) or existing in the Premises at the time of delivery of possession
of the Premises to Tenant by Landlord exclusive only of normal wear and tear.
The provisions of the immediately preceding sentence shall not apply to the
Building basic heating and air conditioning system or to the basic plumbing
system (excluding lavatory, shower, toilet, washbasin, and kitchen facilities
actually located within the Premises as well as base building facilities
installed by Tenant or at Tenant's request as a part of the Tenant's
Improvements).


15.Liens.  Tenant shall not permit any mechanic's, materialmen's or other liens 
   -----  
to be filed against the real property of which the Premises form a part nor
against the Tenant's leasehold interest in the Premises. Landlord shall have
the right at all reasonable times to post and keep posted on the Premises any
notices which it deems necessary for protection from such liens. If any such
liens are filed and Tenant fails to remove such liens within twenty (20) days
after receipt of notice of attachment thereof, Landlord may, without waiving
its rights and remedies based on such breach of Tenant and without releasing
Tenant from any of its obligations, cause such liens to be released by any
means it shall deem proper, including payment in satisfaction of the claim
giving rise to such lien. Tenant shall pay to Landlord at once, upon notice by
Landlord, any sum paid by Landlord to remove such liens, together with
interest at the maximum rate per annum permitted by law from the date of such
payment by Landlord.


16.Entry by Landlord.  Upon reasonable prior notice, Landlord reserves and 
   -----------------
shall at any and all reasonable times (except in the case of emergency, in
which case, Landlord shall have the right for immediate entry without notice)
have the right to enter the Premises for any valid purpose including without
limitation to inspect the same, to supply any service to be provided by
Landlord to Tenant hereunder, to submit said Premises to prospective
purchasers or mortgagors/lenders or, during the last nine (9) months of the
Term of this Lease, to prospective tenants, to post notices of
nonresponsibility, to alter, improve or repair the Premises or any other
portion of the Building, all without being deemed guilty of any eviction of
Tenant
<PAGE>
 
and without abatement of rent, and may, in order to carry out such purposes,
erect scaffolding and other necessary structures where reasonably required by
the character of the work to be performed, provided that the business of
Tenant shall be interfered with as little as is reasonably practicable.
Notwithstanding any provision to the contrary contained in this Lease, any
entry by Landlord or Landlord's agents shall not impair Tenant's operations
more than reasonably necessary, and Tenant shall have the right to have an
employee accompany Landlord and/or its agents at all times that Landlord
and/or its agents are present on the Premises except in the case of an
emergency in which event Landlord shall be entitled to enter the Premises
regardless of whether an employee is available to accompany Landlord. Tenant
hereby waives any claim for damages for any injury or inconvenience to or
interference with Tenant's business, any loss of occupancy or quiet enjoyment
of the Premises, and any other loss occasioned thereby except to the extent
caused by the gross negligence or willful misconduct of Landlord, its agents,
employees or contractors. For each of the aforesaid purposes, Landlord shall
at all times have and retain a key with which to unlock all of the doors in,
upon and about the Premises excluding Tenant's vaults, safes, and security
areas, and Landlord shall have the means which Landlord may deem proper to
open said doors in an emergency in order to obtain entry to the Premises, and
any entry to the Premises obtained by Landlord by any of said means, or
otherwise, shall not under any circumstances be construed or deemed to be a
forcible or unlawful entry into, or a detainer of, the Premises, or an
eviction of Tenant from the Premises or any portion thereof, and any damages
caused on account thereof shall be paid by Tenant except to the extent caused
by the gross negligence or willful misconduct of Landlord, its agents,
employees or contractors. It is understood and agreed that no provision of
this Lease shall be construed as obligating Landlord to perform any repairs,
alterations or decorations except as otherwise expressly agreed herein to be
performed by Landlord. Landlord shall attempt in the exercise of its rights
under this Paragraph 16 to minimize any disturbance of Tenant's use and
possession of the Premises and to provide as much notice to Tenant as may be
reasonably possible prior to any such exercise of Landlord's rights under this
Paragraph 16.


17.Utilities and Services.  Landlord agrees, during the Term, to furnish to 
   ----------------------
the Premises Monday through Friday, 8:00 a.m. through 5:30 p.m., holidays
excepted, reasonable quantities of electric current for normal lighting and
fractional horsepower office machines, water for lavatory and drinking
purposes, heat and air conditioning required in Landlord's reasonable judgment
for the comfortable use and occupancy of the Premises, washing of windows with
reasonable frequency as reasonably determined by Landlord and elevator service
by non attended automatic elevators. Landlord shall not be liable for, and
Tenant shall not be entitled to any abatement or reduction of rent by reason
of Landlord's failure to furnish any of the foregoing when such failure is
caused by accident, breakage, repairs, strikes, lockouts or other labor
disturbances or labor disputes of any character, or for other causes beyond
Landlord's reasonable control. Landlord's cost of providing services pursuant
to this Paragraph 17, shall be part of Operating Expenses to the extent not
expressly excluded pursuant to the provisions of Paragraph 5.1. Tenant hereby
waives the provisions of California Civil Code Section 1932(1) or any other
applicable existing or future law, ordinance or governmental regulation
permitting the termination of this Lease due to the interruption or failure of
or inability to provide any services required to be provided by Landlord
hereunder. Landlord shall provide Tenant access to the Premises on a twenty-
four (24) hour per day basis, subject to events beyond Landlord's reasonable
control. Notwithstanding any provision to the contrary of this Paragraph 17,
pursuant to the provisions of Paragraph 5.2, Tenant is to contract directly
for and obtain (and Landlord is to have no responsibility for) all utilities
and janitorial services and supplies.
<PAGE>
 
     If water, gas, electric current, heat or air conditioning fail to be
provided to the Premises and the Premises becomes completely untenable and
unusable by Tenant and such failure (i) continues for in excess of seven (7)
consecutive business days and (ii) results from the gross negligence or
intentional misconduct of Landlord, Tenant shall be entitled to give notice to
Landlord ("Initial Notice") specifying such situation (the "Abatement Event").
If Landlord has not cured such Abatement Event within three (3) business days
after receipt of the Initial Notice, or in the case of  an Abatement Event which
cannot reasonably be cured within three (3) business days, in the event that
Landlord has not commenced to cure such Abatement Event within three (3)
business days and thereafter diligently continue such cure to completion, Tenant
may deliver an additional, notice to Landlord (the "Additional Notice")
specifying such uncured Abatement Event and Tenants intention to abate the
payment of Monthly Basic Rent and Parking Lot Rent under this Lease.  If
Landlord does not cure the Abatement Event within two (2) business days after
receipt of the Additional Notice, or in the case of an Abatement Event not
reasonably curable within such two (2) business days, in the event that Landlord
fails to commence to cure such Abatement Event within such two (2) business
days, (in each case, the date of expiration of the two (2) business days being
referred to as the "Abatement Date"), Tenant may, upon written notice to
Landlord, immediately abate the Monthly Basic Rent, the Parking Lot Rent and the
Operating Rent payable with respect to the Premises for the period beginning on
the Abatement Date and the total nonuse of the Premises by Tenant to the earlier
of the date Landlord cures such Abatement Event or the Tenant recommences the
use of the Premises or any portion of the Premises.  In the event that Tenant
abates the payment of Monthly Basic Rent, the Parking Lot Rent and/or the
Operating Rent, on the basis of the provisions immediately above and such
provisions allowing abatement have not been fully and completely satisfied,
Tenant shall be in default pursuant to this Lease and Landlord shall be entitled
to all rights and remedies in connection with such default.


18.Indemnification.
   ---------------

18.1 To the fullest extent permitted by law, and except to the extent caused by
the gross negligence or willful misconduct of Landlord, its agents, employees or
contractors, Tenant hereby agrees to defend, indemnify, protect and hold
Landlord harmless against and from any and all loss, cost, damage or liability
arising in whole or in part from Tenant's use of the Premises or the conduct of
its business or from any activity, work, or thing done, permitted or suffered by
Tenant, its agents, contractors, employees or invitees in or about the Premises,
Building and/or Site, and hereby agrees to further indemnify and hold harmless
Landlord against and from any and all loss, cost, damage or liability arising in
whole or in part from any breach or default in the performance of any obligation
on Tenant's part to be performed under the terms of this Lease or arising from
any act, neglect, fault or omission of Tenant, or of its agents, employees or
invitees, and from and against all costs, reasonable attorneys' fees, expenses
and liabilities incurred for such claim or any action or proceeding brought
thereon.  In case any action or proceeding is brought against Landlord by reason
of any such claim, Tenant upon notice from Landlord hereby agrees to defend the
same at Tenant's expense by counsel reasonably approved in writing by Landlord.
Tenant, as a material part of the consideration to Landlord, hereby assumes all
risk of damage to property or injury to persons in, upon or about the Premises
from any cause whatsoever except to the extent caused by Landlord's gross
negligence, intentional misconduct or the failure of Landlord to observe any of
the terms and conditions of this Lease and such failure has persisted for an
unreasonable period of time after written 
<PAGE>
 
notice of such failure, and Tenant hereby waives all its claims in respect
thereof against Landlord.

18.2 Landlord shall indemnify Tenant and hold it harmless from any loss by
reason of injury to person or property to the extent such injury is caused by
the gross negligence or intentional misconduct of Landlord or its agents,
employees or contractors, including without limitation any liability or injury
to the person or property of Landlord, its officers, directors, partners,
employees, agents, invitees or guests. Nothing herein shall relieve Tenant of
liability for its own willful acts or negligence.


19.Damage to Tenant's Property.  Notwithstanding the provisions of Paragraph 18 
   --------------------------- 
to the contrary, except to the extent caused by the gross negligence or
willful misconduct of Landlord, its agents, employees or contractors, Landlord
or its agents shall not be liable for any damage to property entrusted to
employees of the Building (except by reason of the gross negligence of such
employees), nor for loss of or damage to any property by theft or otherwise,
nor for any injury or damage to persons or property resulting from fire,
explosion, falling plaster, steam, gas, electricity, water or rain which may
leak from any part of the Building or from the pipes, appliances or plumbing
works therein or from the roof, street or sub-surface or from any other place
or resulting from dampness or any other patent or latent cause whatsoever.
Landlord or its agents shall not be liable for for interference with the light, 
air, view or intangible characteristics or qualities of the Premises. Tenant
shall give prompt notice to Landlord in case of fire or accidents in the
Premises or in the Building or of defects known to Tenant therein or in the
fixtures or equipment located therein. Further, neither Landlord nor any
partner, director, officer, agent, servant or employee of Landlord shall be
liable: (i) for any such damage caused by other tenants or persons in, upon or
about the Building, or caused by operations in the construction of any
private, public or quasi-public work (the limitations of liability set forth
in this Clause (i) shall not apply to any damage or liability caused by the
gross negligence or intentional misconduct of Landlord or its agents,
employees or contractors); or (ii) for consequential damages, including lost
profits, of Tenant or any person claiming through or under Tenant.


20.Insurance.
   ---------

20.1 During the Term hereof, Tenant, at its sole expense, shall obtain and keep
in force the following insurance:

(a)     Commercial general liability insurance naming the Landlord as an
additional insured against any and all claims for bodily injury and property
damage occurring in, or about the Premises arising out of Tenant's use and
occupancy of the Premises. Such insurance shall have a combined single limit
of not less than Two Million Dollars ($2,000,000.00) per occurrence with a
Five Million Dollars ($5,000,000.00) - aggregate limit. Such liability
insurance shall be primary and not contributing to any insurance available to
Landlord and Landlord's insurance shall be in excess thereto. In no event
shall the limits of such insurance be considered as limiting the liability of
Tenant under this Lease.

(b)     Personal property insurance insuring all equipment, trade fixtures,
inventory, fixtures and personal property located on or in the Premises for
perils covered by the causes of loss - special form (all risk) and in addition,
coverage for flood, and boiler and machinery (if applicable).  Such insurance
shall be written on a replacement cost basis in an amount equal to the full
replacement value of the aggregate of the foregoing less any applicable
deductible.
<PAGE>
 
(c)     Workers' compensation insurance in accordance with statutory law.

(d)     Loss of income and extra expense insurance in such amounts as will
reimburse Tenant for direct or indirect loss of earnings attributable to all
perils commonly insured against by prudent tenants or attributable to prevention
of access to the Premises or to the Building as result of such perils.

(e)     Any other form or forms of insurance as Tenant, Landlord, or Landlord's
mortgagees or ground or primary lessors may reasonably require from time to time
(with additions not to be required more than once in any Lease Year) in form, in
amounts, and for insurance risks against which a prudent tenant of a comparable
size and in a comparable business would protect itself.

20.2 The policies required to be maintained by Tenant shall be with companies
rated AX or better in the most current issue of Best's Insurance Reports.
Insurers shall be licensed to do business in the state in which the Premises are
located and domiciled in the USA.  Any deductible amounts under any insurance
policies required hereunder shall not exceed Ten Thousand Dollars ($10,000).
Certificates of insurance shall be delivered to Landlord prior to the Lease
Commencement Date and annually thereafter at least thirty (30) days prior to the
expiration date of the old policy.  Tenant shall have the right to provide
insurance coverage which it is obligated to carry pursuant to the terms hereof
in a blanket policy, provided such blanket policy expressly affords coverage to
the Premises and to Landlord as required by this Lease.  Each policy of
insurance shall provide that Landlord and Landlord's managing agent (and any
mortgagee) are additional insureds and shall provide notification to Landlord at
least thirty (30) days prior to any cancellation or modification to reduce the
insurance coverage.

20.3 During the Term hereof, Landlord shall insure the Building (excluding any
property which Tenant is obligated to insure under Subparagraph 20.l(b) hereof
but including the Landlord's Work and Tenant's Improvements) against damage with
All Risk insurance in the amount of the full replacement cost of the Building
and public commercial liability insurance, all in such amounts and with such
deductibles as Landlord considers appropriate and consistent with the provisions
of Paragraph 20.8.  Landlord may, but shall not be obligated to, obtain and
carry any other form or forms of insurance as it or Landlord's mortgagees may
determine advisable.  Landlord shall not be required to maintain earthquake
coverage.  Notwithstanding any contribution by Tenant to the cost of insurance
premiums, as provided herein, Tenant acknowledges that it has no right to
receive any proceeds from any insurance policies carried by Landlord.

20.4 Tenant will not knowingly keep, use, sell, or offer for sale in, or upon,
the Premises any article which may be prohibited by any insurance policy
periodically in force covering the Building.  If Tenant's occupancy or business
in, or on, the Premises, whether or not Landlord has consented to the same,
results in any increase in premiums for the insurance periodically carried by
Landlord with respect to the Building, Tenant shall pay any such increase in
premiums as additional rent within twenty (20) days after being billed therefor
by Landlord. In determining whether increased premiums are a result of Tenant's
use of the Premises, a schedule issued by the organization computing the
insurance rate on the Building or the Premises showing the various components of
such rate, shall be conclusive evidence of the several items and charges which
make up such rate. Tenant shall promptly comply with all reasonable requirements
of the insurance authority or any present or future insurer relating to the
Premises.
<PAGE>
 
20.5 If any of Landlord's insurance policies shall be canceled or cancellation
shall be threatened or the coverage thereunder reduced or threatened to be
reduced in any way because of the specific use of the Premises or any part
thereof by Tenant or any assignee or sub-tenant of Tenant or by anyone Tenant
permits on the Premises and, if Tenant fails to remedy the condition giving rise
to such cancellation, threatened cancellation, reduction of coverage, threatened
reduction of coverage, increase in premiums, or threatened increase in premiums,
within 72 hours after receipt of notice thereof, Landlord may, at its option,
either terminate this Lease or enter upon the Premises and attempt to remedy
such condition, and Tenant shall promptly pay the cost thereof to Landlord as
additional rent. Landlord shall not be liable for any damage or injury caused to
any property of Tenant or of others located on the Premises resulting from such
entry. If Landlord is unable, or elects not, to remedy such condition, then
Landlord shall have all of the remedies provided for in this Lease in the event
of a default by Tenant. Notwithstanding the foregoing provisions of this
Subparagraph 20.5, if Tenant fails to remedy as aforesaid, Tenant shall be in
default of its obligation hereunder and Landlord shall have no obligation to
remedy such default.

20.6 Landlord and Tenant hereby mutually waive their respective rights of
recovery against each other for any loss of, or damage to, either parties'
property, to the extent that such loss or damage is insured by an insurance
policy required to be in effect at the time of such loss or damage. Each party
shall obtain any special endorsements, if required by its insurer whereby the
insurer waives its rights of subrogation against the other party. The provisions
of this clause shall not apply in those instances in which waiver of subrogation
would cause either party's insurance coverage to be voided or otherwise made
uncollectible.

20.7 In the event Tenant does not purchase the insurance required by this Lease
or keep the same in full force and effect, Landlord may, but shall not be
obligated to, purchase the necessary insurance and pay the premium. The Tenant
shall repay to Landlord, as additional rents the amount so paid promptly upon
demand. In addition, Landlord may recover from Tenant and Tenant agrees to pay,
as additional rent, any and all reasonable expense (including attorneys' fees)
and damages which Landlord may sustain by reason of the failure of Tenant to
obtain and maintain such insurance.

20.8 Landlord shall maintain insurance coverage comparable to insurance coverage
maintained by prudent landlords of buildings in the area in which the Building
is located that are comparable to the Building, and which in any event includes
fire and extended coverage insurance for the Building and commercial liability
coverage.


21.Damage or Destruction.
   ---------------------

21.1 In the event that the Premises is damaged by fire or other casualty which
is covered under insurance pursuant to the provisions of  the foregoing
paragraph, Landlord shall restore such damage provided that: (i) the destruction
of the Building does not exceed fifty percent (50%) of the then replacement
value of the Building; (ii) insurance proceeds are available (inclusive of any
deductible amounts) to pay one hundred percent (100%) of the cost of
restoration; and (iii) in the reasonable judgment of Landlord, the restoration
can be completed within two hundred and seventy (270) days after the date of the
damage or casualty under the laws and regulations of the state, federal, county
and municipal authorities having jurisdiction.  Landlord shall notify Tenant
whether or not the Premises will 
<PAGE>
 
be restored under this paragraph within thirty (30) days of the occurrence of
the casualty. The deductible amount of any insurance coverage shall be paid by
Tenant. If such conditions apply so as to require Landlord to restore such
damage pursuant to this paragraph, this Lease shall continue in full force and
effect, unless otherwise agreed in writing by Landlord and Tenant. Tenant
shall be entitled to a proportionate reduction of Monthly Basic Rent, Parking
Lot Rent and Operating Rent at all times during which Tenant's use of the
Premises is interrupted, such proportionate reduction to be based on the
extent to which the damage and restoration efforts actually interfere with
Tenant's business in the Premises. Tenant's right to a reduction of Rent
hereunder shall be Tenant's sole and exclusive remedy in connection with any
such damage. Notwithstanding the foregoing, if Landlord elects to terminate
this Lease pursuant to this Subparagraph 21.1, if within thirty (30) days
after receipt of Landlord's notice Tenant elects to provide the funds
necessary to make up the shortage (or absence) of insurance proceeds and
provides Landlord with reasonable assurance thereof, Landlord shall restore
the Premises as provided in this Subparagraph provided that the Premises are
reasonably subject to restoration within two hundred seventy (270) days
following the date on which the casualty occurs. Tenant in connection with
such election, shall have the right to exercise the first or second (as
applicable) option to extend the Term provided by Paragraph 2.3 above,
provided that Tenant otherwise meets all requirements necessary for such
exercise.

21.2 In the event that the Building is damaged by casualty and Landlord is not
required to restore such damage in accordance with the provisions of  the
immediately preceding paragraph, Landlord shall have the option to either (i)
repair or restore such damage, with the Lease continuing in full force and
effect, but Monthly Basic Rent, Parking Lot Rent and Operating Rent to be
proportionately abated as provided  above; or (ii) give notice to Tenant at any
time within thirty (30) days after the occurrence of such damage terminating
this Lease as of a date to be specified in such notice which date shall not be
less than thirty (30) nor more than sixty (60) days after the date on which such
notice of termination is given.  In the event of the giving of such notice of
termination, this Lease shall expire and all interest of Tenant in the Premises
shall terminate on the date so specified in such notice and the Rent, reduced by
any proportionate reduction in Monthly Basic Rent, Parking Lot Rent and
Operating Rent as provided for above, shall be paid to the date of such
termination.  Notwithstanding the foregoing, if within thirty (30) days after
receipt of Landlord's notice, Tenant elects to advance to Landlord the funds
necessary to make up the shortage (or absence) in insurance proceeds and
provides Landlord with reasonable assurance thereof and the restoration can be
completed in a two hundred seventy (270) day period, as reasonably determined by
Landlord, Landlord shall restore the Premises as provided in the immediately
preceding paragraph.  Tenant in connection with any such election, shall have
the right to exercise the first or second (as applicable) option to extend the
Term provided by Paragraph 2.3 above, provided that Tenant otherwise satisfies
all requirements in connection with such exercise.

21.3 Notwithstanding the foregoing, either Landlord or Tenant may terminate this
Lease if the Building damaged by fire or other casualty (and Landlord's
reasonably estimated cost of restoration of the Premises exceeds ten percent
(10%) of the then replacement value of the Building) and such damage or casualty
occurs during  the last twelve (12) months of the Term of this Lease (or the
Term of any renewal option, if applicable) by giving the other notice thereof at
any time within thirty (30) days following the occurrence of such damage or
casualty.  Such notice shall specify the date of such termination, which date
shall not be less than thirty (30) nor more than sixty (60) days following the
date on which such notice of termination is given.  In the event of the giving
of such notice of termination, this Lease shall expire and all interest of
<PAGE>
 
Tenant in the Premises shall terminate on the date so specified in such notice
and the Rent shall be paid to the date of such termination.  Notwithstanding the
foregoing to the contrary, Landlord shall not have the right to terminate this
Lease if damage or casualty occurs during the last twelve (12) months of the
Term if Tenant timely exercises its option to extend the Term of this Lease (if
any) within thirty (30) days after the date of such damage or casualty.

21.4 In the event that the destruction to the Premises cannot be restored as
required herein under applicable laws and regulations within two hundred seventy
(270) days of the damage or casualty, notwithstanding the availability of
insurance proceeds, or if Landlord commences the restoration but does not
substantially complete the restoration within three hundred (300)days, in either
case Tenant shall have the right to terminate this Lease by giving the Landlord
notice thereof within thirty (30) days of date of the occurrence of such
casualty, or within thirty (30) days after the end of the three hundred (300)
day period, as applicable, specifying the date of termination which shall not be
less than thirty (30) days nor more than sixty (60) days following the date on
which such notice of termination is given.  In the event of the giving of such
notice of termination, this Lease shall expire and all interest of Tenant in the
Premises shall terminate on the date so specified in such notice and the Rent,
reduced by any proportionate reduction in Monthly Basic Rent, Parking Lot Rent
and Operating Rent as provided for above, shall be paid to the date of such
termination.

21.5 Upon any termination of this Lease under any of the provisions of this
Paragraph 21, the parties shall be released thereby without further obligation
to the other from the date possession of the Premises is surrendered to Landlord
except for items which have already accrued and are then unpaid.

21.6 Tenant shall not be released from any of its obligations under this Lease
except to the extent and upon the conditions expressly stated in this Paragraph
21. Notwithstanding anything to the contrary contained in this Paragraph 21,
should Landlord be delayed or prevented from repairing or restoring the damaged
Premises within three hundred (300) days after the occurrence of such damage or
destruction by reason of acts of God, war, governmental restrictions, inability
to procure the necessary labor or materials, or other cause beyond the control
of Landlord, Landlord shall be relieved of its obligation to make such repairs
or restoration and Tenant shall be released from its obligations under this
Lease as of the end of said three hundred (300) day period.

21.7 It is hereby understood that if Landlord is obligated to or elects to
repair or restore as herein provided, Landlord shall be obligated to make
repairs or restoration only of those portions of the Building and the Premises
which were originally provided at Landlord's expense (including, without
limitation, Landlord's Work or the Tenant's Improvements) or which were insured
by either party and the proceeds of such insurance have been received by
Landlord, and the repair and restoration of items not provided at Landlord's
expense shall be the obligation of Tenant.

21.8 Tenant hereby waives California Civil Code Sections 1932(2) and 1933(4),
providing for termination of hiring upon destruction of the thing hired and
Sections 1941 and 1942, providing for repairs to and of Premises.


22.Eminent Domain.
   --------------
<PAGE>
 
22.1 In case the whole of the Premises, or such part thereof as shall
substantially interfere with Tenant's use and occupancy thereof, shall be taken
for any public or quasi-public purpose by any lawful power or authority by
exercise of the right of appropriation, condemnation or eminent domain, or sold
to prevent such taking, either party shall have the right to terminate this
Lease effective as of the date possession is required to be surrendered to said
authority. Tenant shall not assert any claim against Landlord or the taking
authority for any compensation because of such taking (provided that Tenant may
present a separate claim for Tenant's relocation costs, moving expenses, loss of
goodwill, the unamortized cost of any Changes paid for by Tenant and lost
personal property, so long as such claim does not diminish any award otherwise
available to Landlord), and Landlord shall be entitled to receive the entire
amount of any award without deduction for any estate or interest of Tenant.  In
the event the amount of property or the type of estate taken shall not
substantially interfere with the conduct of Tenant's business, Landlord shall be
entitled to the entire amount of the award without deduction for any estate or
interest of Tenant. If this Lease is not so terminated, Landlord shall promptly
proceed to restore the Premises to substantially their same condition prior to
such partial taking, and a proportionate allowance shall be made to Tenant for
the rent corresponding to the time during which, and to the part of the Premises
of which, Tenant shall be so deprived on account of such taking and restoration.
Nothing contained in this Paragraph shall be deemed to give Landlord any
interest in any award separately made to Tenant for the taking of personal
property and trade fixtures belonging to Tenant or for relocation costs incurred
by Tenant in relocating Tenant's business, moving expenses, loss of goodwill and
the unamortized cost of any Changes paid for by Tenant.

22.2 In the event of taking of the Premises or any part thereof for temporary
use, (i) this Lease shall be and remain unaffected thereby and rent shall not
abate, and (ii) Tenant shall be entitled to receive for itself such portion or
portions of any award made for such use with respect to the period of the taking
which is within the Term, provided that if such taking shall remain in force at
the expiration or earlier termination of this Lease, Tenant shall then pay to
Landlord a sum equal to the reasonable cost of performing Tenant's obligations
under Paragraph 14 with respect to surrender of the Premises and upon such
payment shall be excused from such obligations. For purpose of this Subparagraph
22.2, a temporary taking shall be defined as a taking for a period of 270 days
or less.

22.3 Landlord and Tenant each hereby waive the provisions of California Code of
Civil Procedure Section 1265.130 and any other applicable existing or future
law, ordinance or governmental regulation providing for, or allowing either
party to petition the courts of the state of California for, a termination of
this lease upon a partial taking of the Premises and/or the Building.

23. Bankruptcy.  If Tenant shall file a petition in bankruptcy under any 
    ----------
Chapter of federal bankruptcy law as then in effect, or if Tenant be
adjudicated a bankrupt in involuntary bankruptcy proceedings and such
adjudication shall not have been vacated within sixty (60) days from the date
thereof, or if a receiver or trustee be appointed of Tenant's property and the
order appointing such receiver or trustee not be set aside or vacated within
sixty (60) days after the entry thereof, or if Tenant shall assign Tenant's
estate or effects for the benefit of creditors, or if this Lease shall
otherwise by operation of law pass to any person or persons other than Tenant,
then and in any such event Landlord may, if Landlord so elects, with or
without notice of such election and with or without entry or action by
Landlord, forthwith terminate this Lease. Notwithstanding any other provisions
of this Lease, Landlord, in addition to any and all rights and 
<PAGE>
 
remedies allowed by law or equity, shall upon such termination be entitled to
recover damages in the amount provided in Subparagraph 24.2 below and neither
Tenant nor any person claiming through or under Tenant or by virtue of any
statute or order of any court shall be entitled to possession of the Premises
but shall forthwith quit and surrender the Premises to Landlord. Nothing
herein contained shall limit or prejudice the right of Landlord to prove and
obtain as damages by reason of any such termination an amount equal to the
maximum allowed by any statute or rule of law in effect at the time when, and
governing the proceedings in which, such damages are to be proved, whether or
not such amount be greater, equal to, or less than the amount of damages
recoverable under the provisions of this Paragraph 23.


24.Defaults and Remedies.
   ---------------------

24.1 The occurrence of any one or more of the following events shall constitute
a default hereunder by Tenant:

(a)     The vacation or abandonment of the Premises by Tenant. Abandonment is
herein defined to include, but is not limited, to, any absence by Tenant from
the Premises for ten (10) days or longer while in default of any provision of
this Lease.

(b)     The failure by Tenant to make any payment of Basic Rent, Parking Lot
Rent, Operating Rent, other rent or sums deemed herein as additional rent, or
any other payment required to be made by Tenant hereunder as and when due,
where such failure continues for a period of five (5) business days after
written notice thereof from Landlord to Tenant.

(c)     The failure by Tenant to observe or perform any of the express or
implied covenants or provisions of this Lease to be observed or performed by
Tenant, other than as specified in Subparagraph 24.1(a) or 24.1(b) above,
where such failure shall continue for a period of thirty (30) days after
written notice thereof from Landlord to Tenant; provided, however, that any
such notice shall be in lieu of, and not in addition to, any notice required
under California Code of Civil Procedure 1161; provided, further, that if the
nature of Tenant's default is such that more than thirty (30) days are
reasonably required for its cure, then Tenant shall not be deemed to be in
default if Tenant shall commence such cure within said thirty-day period and
thereafter diligently and without interruption prosecute such cure to
completion.

(d)     (1) The making by Tenant of any general assignment for the benefit of
creditors; (2) the filing by or against Tenant of a petition to have Tenant
adjudged a bankrupt or a petition for reorganization or arrangement under any
law relating to bankruptcy (unless, in the case of a petition filed against
Tenant, the same is dismissed within sixty (60) days); (3) the appointment of a
trustee or receiver to take possession of substantially all of Tenant's assets
located at the Premises or of Tenant's interest in this Lease, where possession
is not restored to Tenant within sixty (60) days; or (4) the attachment,
execution or other judicial seizure of substantially all of Tenant's assets
located at the Premises or of Tenant's interest in this Lease where such seizure
is not discharged within sixty (60) days.

(e)     The failure by Tenant within ten (10) days after receipt of written
demand of Landlord to restore the security deposit by deposit of additional
cash or an additional letter of credit as required 
<PAGE>
 
pursuant to the provisions of Paragraph 6.1 of this Lease.

24.2 In the event of any such default by Tenant, in addition to any other
remedies available to Landlord at law or in equity, Landlord shall have the
immediate option to terminate this Lease and all rights of Tenant hereunder.
Upon such termination of Tenant's right to possession of the Premises, this
Lease shall terminate and Landlord shall be entitled to recover damages from
Tenant as provided in California Civil Code Section 1951.2 or any other
applicable existing or future law, ordinance or regulation providing for
recovery of damages for such breach, including but not limited to the
following:

(a)     the worth at the time of award of any unpaid rent which had been
earned at the time of such termination; plus

(b)     the worth at the time of award of the amount by which the unpaid rent
which would have been earned after termination until the time of award exceeds
the amount of such rental loss that Tenant proves could have been reasonably
avoided; plus

(c)     the worth at the time of award of the amount by which the unpaid rent
for the balance of the Term after the time of award exceeds the amount of such
rental loss that Tenant proves could be reasonably avoided; plus

(d)     any other amount necessary to compensate Landlord for all the detriment
proximately caused by Tenant's failure to perform his obligations under this
Lease or which in the ordinary course of things would be likely to result
therefrom.

     As used in Subparagraphs 24.2(a) and 24.2(b) above, the "worth at the time
of award" is computed by allowing interest at the maximum rate permitted by law
per annum.  As used in Subparagraph 24.2(c) above, the worth at the time of
award is computed by discounting to present value such amount at the discount
rate of the Federal Reserve Bank of San Francisco at the time of award plus one
percent (1%).

24.3 If a default exists under this Lease, Landlord shall also have the remedy
described in California Civil Code Section 1951.4 (Landlord may continue this
Lease in effect after Tenant has breached this Lease and abandoned the Premises
and recover rent as it becomes due; provided, however that Tenant has the right
to sublet or assign this Lease, subject only to reasonable limitations).  Acts
of maintenance or preservation or efforts to relet the Premises or the
appointment of a receiver upon initiative of Landlord to protect Landlord's
interest under this Lease shall not constitute a termination of Tenant's right
to possession.


24.4 During the continuance of a default beyond applicable cure periods,
Landlord may enter the Premises without terminating this Lease and, upon five
(5) days prior written notice to Tenant, remove all Tenant's personal property,
any Changes and trade fixtures from the Premises and store them at Tenant's risk
and expense.  If Landlord removes such property from the Premises and stores it
at Tenant's risk and expense, and if Tenant fails to pay the cost of such
removal and storage after written demand therefor and/or to pay any rent then
due, then after the property has been stored for a period of thirty (30)-days or
more Landlord may sell such property at public or private sale, in the manner
and at such times and places as Landlord deems commercially reasonable following
reasonable notice to Tenant of the time and place 
<PAGE>
 
of such sale. The proceeds of any such sale shall be applied first to the
payment of the expenses for removal and storage of the property, the
preparation for and the conducting of such sale, and for reasonable attorneys'
fees and other legal expenses incurred by Landlord in connection therewith;
and the balance shall be applied to any past due amount owing hereunder.

     Tenant hereby waives all claims for damages that may be caused by
Landlord's reentering and taking possession of the Premises or removing and
storing Tenant's personal property pursuant to this Paragraph 24, and Tenant
shall hold Landlord harmless from and against any loss, cost or damage resulting
from any such act. No reentry by Landlord shall constitute or be construed as a
forcible entry by Landlord.

24.5 All rights, options' and remedies of Landlord contained in this Lease
shall be construed and held to be cumulative, and no one of them shall be
exclusive of the other, and Landlord shall have the right to pursue any one or
all of such remedies or any other remedy or relief which may be provided by
law, whether or not stated in this Lease. No waiver of any default of Tenant
hereunder shall be implied from any acceptance by Landlord of any rent or
other payments due hereunder or any omission by Landlord to take any action on
account of such default if such default persists or is repeated, and no
express waiver shall affect defaults other than as specified in said waiver.
The consent or approval or Landlord to or of any act by Tenant requiring
Landlord's consent or approval shall not be deemed to waive or render
unnecessary Landlord's consent or approval to or of any subsequent similar
acts by Tenant.

24.6 If Landlord is in default of any obligations under this Lease, and fails to
commence to cure within thirty (30) days after receipt of written notice from
Tenant which notice shall specify the nature of Landlord's default, Tenant shall
be entitled to exercise any and all remedies available to Tenant at law or in
equity except to the extent expressly waived by Tenant pursuant to this Lease.


25.Assignment and Subletting.  Tenant shall not voluntarily assign or encumber 
   -------------------------
its interest in this Lease or in the Premises, or sublease all or any part of
the Premises, or allow any other person or entity to occupy or use all or any
part of the Premises, without first obtaining Landlord's prior written
consent, which consent shall not be unreasonably withheld or delayed. Any
assignment, encumbrance or sublease without Landlord's prior written consent
shall be voidable, at Landlord's election, and shall constitute a default. If
Tenant is a partnership, a withdrawal or change, voluntary, involuntary or by
operation of law of any partner, or the dissolution of the partnership, shall
be deemed a voluntary assignment. If Tenant consists of more than one person,
a purported assignment, voluntary or involuntary or by operation of law from
one person to the other shall be deemed a voluntary assignment. If Tenant is a
nonpublic corporation, any dissolution, merger, consolidation or other
reorganization of Tenant, or sale or other transfer of a controlling
percentage of the capital stock of Tenant, or the sale of at least fifty
percent (50%) of the value of the assets of Tenant shall be deemed a voluntary
assignment. If Tenant is a publicly traded corporation, any sale or other
transfer of a controlling percentage of the capital stock of Tenant in one
transaction or a series of related transactions to one person or entity or two
or more affiliated entities and/or persons shall be deemed a voluntary
assignment which requires Landlord's consent. Except as set forth in the
sentence immediately above, the transfer of publicly traded shares of Tenant,
whether or not in the aggregate constituting a transfer of a controlling
percentage of the capital stock of Tenant, shall not constitute a voluntary
assignment. No consent to any assignment, encumbrance, or sublease shall
<PAGE>
 
constitute a further waiver of the provisions of this Paragraph. No later than
thirty (30) days prior to the effective date of the proposed assignment or
sublease, Tenant shall notify Landlord in writing of Tenant's intent to
assign, encumber, or sublease, the name of the proposed assignee or sublessee,
information concerning the financial responsibility of the proposed assignee
or sublessee and the terms of the proposed assignment or subletting, and
Landlord shall, within fifteen (15) days of receipt of such written notice as
well as any additional information requested by Landlord concerning the
proposed assignee's or sublessee's financial responsibility, elect one of the
following:

(i)     Consent to such proposed assignment, encumbrance or sublease;

(ii)    Refuse such consent, which refusal shall be on reasonable grounds,
        including but not limited to those matters set forth hereinbelow;

(iii)   In the case of an assignment, elect to terminate this Lease. In the
case of a sublease elect to terminate this Lease, but only in the event that a
request to sublet would have the result of in excess of fifty percent (50%) of
the rentable square feet of the Premises being subject to sublease at any time
during the Term. In the event that Landlord elects to terminate the Lease by
reason of a proposed assignment or by reason of a proposed sublease as
described immediately above, Landlord shall give notice of such election
("Recapture Notice") to Tenant within fifteen (15) days after receipt of
written notice from Tenant of the proposed assignment or sublease as well as
any additional information requested by Landlord concerning the proposed
assignee's or sublesee's financial responsibility. In the case of a proposed
sublease (and not a proposed assignment), in the event that Landlord gives a
Recapture Notice, Tenant shall be entitled to rescind its proposed sublease
(and thus avoid termination of the Lease) by giving written notice to Landlord
of such recission within five (5) days following receipt by Tenant of the
Recapture Notice. In the event that Tenant fails to give such notice within
such five (5) days, Tenant shall be considered to have waived its right to
give such recission notice. The Recapture Notice, if given, shall in addition
to stating Landlord's election to terminate this Lease, state a date of
termination of the Lease which, in no event, shall be earlier than thirty (30)
days following the date on which the Recapture Notice is given nor later than
90 days following the date on which the Recapture Notice is given.

     Without limiting the other instances in which it may be reasonable for
Landlord to withhold its consent to an assignment or subletting, Landlord and
Tenant acknowledge that it shall be reasonable for Landlord to withhold its
consent in the following instances: (i) if at the time consent is requested or
at any time prior to the granting of consent, Tenant is in default, beyond any
applicable cure period, under this Lease or would be in default under this Lease
but for the pendency of any grace or cure period under Paragraph 24 above; (ii)
if the proposed assignee or sublessee is a governmental agency; (iii) if, in
Landlord's reasonable judgment, the use of the Premises by the proposed assignee
or sublessee (1) would be inconsistent with Paragraph 7 of this Lease, (2) would
contemplate any alterations which would lessen the value of the leasehold
improvements in the Premises, (3) would result in more than a reasonable number
of occupants per floor, or (4) would materially require increased services by
Landlord; (iv) if the proposed assignee's or sublessee's credit, character and
business or professional standing does not meet the commercially reasonable
standards of Landlord; (v) the proposed  assignee has a net worth of less than
the net worth of Tenant as of the date of this Lease (in the approximate amount
of Three Hundred Million Dollars ($300,000,000)); or (vi) if Landlord is
currently marketing space in the Building to such proposed 
<PAGE>
 
assignee or sublessee.

     Landlord may require that the rent payable by such assignee or sublessee be
at the then current rental rates for the Premises or comparable premises in the
Building and may require that the assignee remit directly to Landlord on a
monthly basis all monies due to Tenant by said assignee.   Payments with respect
to any sublease, so long as the Tenant is not in default hereunder, may be made
directly to Tenant and Tenant shall then promptly pay to Landlord any amount due
Landlord in connection with such sublease.  In the event that Landlord shall
consent to any assignment or sublease under the provisions of this Paragraph 25,
Tenant shall pay Landlord's reasonable processing costs and attorneys' fees
incurred in giving such consent, not to exceed one thousand dollars ($1,000) per
request for consent.  If for any proposed assignment or sublease Tenant receives
rent or other consideration, either initially or over the term of the assignment
or sublease, in excess of the rent and monthly amortization of Transfer Costs
(defined below) called for hereunder, or, in case of the sublease of a portion
of the Premises, in excess of the monthly amortization of all Transfer Costs and
such rent fairly allocable to such portion, after appropriate adjustments to
assure that all other payments called for hereunder are taken into account,
Tenant shall pay to Landlord as additional rent hereunder fifty percent (50%) of
all of the excess of each such payment of rent or other consideration received
by Tenant promptly after its receipt. As used herein, "Transfer Costs" shall
mean the aggregate of (i) commercially reasonable brokerage commissions and
attorneys' fees incurred by Tenant in negotiating and documenting such
assignment or sublease and (ii) the actual third party costs incurred by Tenant
in connection with constructing improvements to the Premises directly related to
the assignment or sublease subject, however, to a maximum cost of ten dollars
($10) per rentable square foot.  Such Transfer Costs are to be amortized
(without interest) for the purposes of Tenant's recovery of same from excess
consideration, on a straight-line basis over the remaining initial Term of this
Lease as of the effective date of such assignment or subletting. Landlord's
waiver or consent to any assignment or subletting shall not relieve Tenant from
any obligation under this Lease.

     Notwithstanding any provision to the contrary of this Paragraph 25, Tenant,
without Landlord's prior written consent, may sublet all or any portion of the
Premises or assign this Lease to (i) a corporation controlling, controlled by or
under common control with Tenant; (ii) a successor corporation related to Tenant
by merger, consolidation or non-bankruptcy reorganization provided that if
Tenant is not the surviving corporation, then the surviving corporation shall
have a minimum net worth as of the date of sublease or assignment at least equal
to that of Tenant immediately prior to completion of the subject merger
consolidation or reorganization; or (iii) a purchaser of substantially all of
Tenant's assets, provided that immediately following such purchase, such
purchaser shall have a net worth at least equal to that of Tenant immediately
prior to completion of the subject purchase.  In connection with any such
assignment or sublease, Tenant shall not be relieved of any liability or
obligations pursuant to this Lease.  The entities described in Clauses (i), (ii)
and (iii) above shall sometimes be referred to as a "Permitted Transferee".  In
connection with any transfer to a Permitted Transferee, Tenant shall give
Landlord at least thirty (30) days prior written notice of such intended
transfer and shall provide to Landlord such information and copies of such
documents as Landlord may reasonably request in connection with such proposed
transfer.  Notwithstanding any provision of this Lease to the contrary
including, without limitation, any provision of this Paragraph 25, no assignment
or sublease of this Lease shall relieve Tenant of any of its obligations or
liability pursuant to this Lease.
<PAGE>
 
26.Quiet Enjoyment.  Landlord covenants and agrees that, conditioned upon 
   ---------------
Tenant paying the rent required under this Lease and paying all other charges
and performing all of the covenants and provisions to be observed and
performed by Tenant under this Lease, and subject to the terms and conditions
of this Lease, Tenant shall and may peaceably and quietly have, hold and enjoy
the Premises in accordance with this Lease.


27.Subordination.  Without the necessity of any additional document being 
   -------------
executed by Tenant for the purpose of effecting a subordination, and at the
election of Landlord or any first mortgagee with a lien on the Building or any
ground lessor with respect to the Building, this lease shall be subject and
subordinate at all times to; (a) all ground leases or underlying leases which
may now exist or hereafter be executed affecting the Building or the land upon
which the Building is situated or both, and (b) the lien of any mortgage or
deed of trust which may now exist or hereafter be executed in any amount for
which the Building, land, ground leases or underlying leases, or Landlord's
interest or estate in any of said items is specified as security.
Notwithstanding the foregoing, Landlord shall have the right to subordinate or
cause to be subordinated any such ground leases or underlying leases or any
such liens to this lease. In the event that any ground lease or underlying
lease terminates for any reason or any mortgage or deed of trust is foreclosed
or a conveyance in lieu of foreclosure is made for any reason, Tenant shall,
if requested by the ground lessor, mortgagee or beneficiary, as applicable,
attorn to and become the Tenant of the successor in interest to Landlord and
in such event Tenant's right to possession of the Premises shall not be
disturbed if Tenant is not in default beyond acceptable cure periods and so
long as Tenant shall pay the rent and all other amounts required to be paid to
Landlord pursuant to the terms hereof and observe and perform all of the
provisions of this Lease, unless the Lease is otherwise terminated pursuant to
its terms. Tenant covenants and agrees to execute and deliver, upon demand by
Landlord and in the form reasonably requested by Landlord, any additional
documents evidencing the priority or subordination of this Lease with respect
to any such ground leases or underlying leases or the lien of any such
mortgage or deed of trust. Should Tenant fail to sign and return any such
documents within ten (10) business days of receipt, Tenant shall be in
default, and Landlord may, at Landlord's option, terminate this Lease provided
written notice of such termination is received by Tenant prior to Landlord's
receipt of such documents. In connection with any subordination by Tenant of
its leasehold interest to any future ground lease, or the lien of any mortgage
or deed of trust, Tenant shall be entitled to obtain a non-disturbance
agreement in a form reasonably satisfactory to Tenant providing that Tenant's
right to occupancy of the Premises shall not be disturbed in the event of any
termination of the ground lease or any foreclosure of the lien of the deed of
trust or mortgage. Landlord shall take such action as is reasonable (without
cost to Landlord) so as to cause a non-disturbance agreement to be available
to Tenant in connection with any subordination by Tenant of its leasehold
interest. In connection with the execution of this Lease by Landlord and
Tenant, Landlord shall use its best efforts (without cost to Landlord) to
cause a Subordination and Non-Disturbance Agreement to be made available to
Tenant in a form reasonably acceptable to Tenant within ten (10) days
following the execution and delivery of this Lease by Landlord and Tenant in
connection with any lender or lenders with respect to any deed of trust
currently constituting a lien against the Building and Site.


28.Estoppel Certificate.
   --------------------

28.1 Within ten (10) business days following receipt of Landlord's written
request, Tenant shall execute 
<PAGE>
 
and deliver to Landlord a statement, in a form substantially similar to the
form of Exhibit "C" attached hereto, certifying; (i) the Lease Commencement
        -----------                             
Date; (ii) the fact that this Lease is unmodified and in full force and effect
(or, if there have been modifications hereto, that this Lease is in full force
and effect, as modified, and stating the date and nature of such
modifications); (iii) the date to which the rent and other sums payable under
this Lease have been paid; (iv) the fact that there are no current defaults
under this Lease by either Landlord or Tenant except as specified in such
statement; and (v) such other matters reasonably requested by the requesting
party. Landlord and Tenant intend that any statement delivered pursuant to
this Paragraph 28 may be relied upon by any mortgagee, beneficiary, purchaser
or prospective purchaser of the Building or any interest therein.

28.2 Tenant's failure to deliver such statement within such time shall be
conclusive upon Tenant (i) that this Lease is in full force and effect, without
modification except as may be represented by the requesting party, (ii) that
there are no uncured defaults in the requesting party's performance, and (iii)
that not more than one (1) month's rent has been paid in advance.


29.Rules and Regulations.  Tenant shall faithfully observe and comply with the 
   ---------------------
"Rules and Regulations," a copy of which is attached hereto and marked Exhibit
                                                                       -------
"D", and all reasonable and nondiscriminatory modifications thereof and
---
additions thereto from time to time put into effect by Landlord that do not
increase any obligations or diminish any rights of Tenant. In the event of any
conflict between the terms of this Lease and the Rules and Regulations, the
terms of this Lease shall prevail.


30.Conflict of Laws.  This Lease shall be governed by and construed pursuant to 
   ----------------
the laws of the State of California.


31.Successors and Assigns.  Except as otherwise provided in this Lease, all of 
   ----------------------
the covenants, conditions and provisions of this Lease shall be binding upon
and shall inure to the benefit of the parties hereto and their respective
heirs, personal representative, successors and assigns.


32.Surrender of Premises.  The voluntary or other surrender of this Lease by 
   ---------------------
Tenant, or a mutual cancellation thereof, shall not work a merger, and shall,
at the option of Landlord, operate as an assignment to it of any or all
subleases or subtenancies. Upon the expiration or termination of this Lease,
Tenant shall peaceably surrender the Premises and all alterations and
additions thereto broom-clean, in good order, repair and condition, reasonable
wear and tear, casualty, condemnation, acts of God, Hazardous Materials not
stored, used, released or disposed of by Tenant, its agents, employees,
invitees or contractors and Changes with respect to which Landlord has not
reserved the right to require removal excepted. The delivery of keys to any
employee of Landlord or to Landlord's agent or any employee thereof shall not
be sufficient to constitute a termination of this Lease or a surrender of the
Premises.


33.Professional Fees.
   -----------------

33.1 In the event that Landlord or Tenant should bring suit for the possession
of the Premises, for the recovery of any sum due under this Lease, or because of
the breach of any provisions of this Lease, or for any other relief against
Tenant or Landlord hereunder, or should either party bring suit against the
other with respect to matters arising from or growing out of this Lease, then
all costs and expenses, including 
<PAGE>
 
without limitation, its reasonable professional fees such as appraisers',
accountants' and attorneys' fees, incurred by the prevailing party therein
shall be paid by the other party, which obligation on the part of the other
party shall be deemed to have accrued on the date of the commencement of such
action and shall be enforceable whether or not the action is prosecuted to
judgment.

33.2 Should Landlord be named as a defendant in any suit brought against Tenant
in connection with or arising out of Tenant's occupancy hereunder, Tenant shall
pay to Landlord its costs and expenses incurred in such suit, including without
limitation, its actual and reasonable professional fees such as appraiser's,
accountants' and attorneys' fees.


34.Performance by Tenant.  All covenants and agreements to be performed by 
   ---------------------
Tenant under any of the terms of this Lease shall be performed by Tenant at
Tenant's sole cost and expense and without any abatement of rent, except as
expressly set forth in this Lease. Tenant acknowledges that the late payment
by Tenant to Landlord of any sums due under this Lease will cause Landlord to
incur costs not contemplated by this Lease, the exact amount of such cost
being extremely difficult and impractical to fix. Such costs include, without
limitation, processing and accounting charges, and late charges that may be
imposed on Landlord by the terms of any encumbrance and note secured by any
encumbrance covering the Premises or the Building of which the Premises are a
part. Therefore if, following five (5) business days after Landlord has
notified Tenant that such amount has not been received, any monthly
installment of Monthly Basic Rent is not received by Landlord, or if Tenant
fails to pay any other sum of money due hereunder and such failure continues
for ten (10) days after receipt by Tenant of notice thereof from Landlord,
Tenant shall pay to Landlord, as additional rent, ten percent (10 %) of the
overdue amount as a late charge. Such overdue amount shall also bear interest,
as additional rent, at the maximum rate permissible by law calculated, as
appropriate, from the date either (a) the monthly installment of Monthly Basic
Rent is due, or (b) of receipt of said notice, until the date of payment to
Landlord. Landlord's acceptance of any late charge or interest shall not
constitute a waiver of Tenant's default with respect to the overdue amount or
prevent Landlord from exercising any of the other rights and remedies
available to Landlord under this Lease or any law now or hereafter in effect.
Further, in the event such late charge is imposed by Landlord for three (3)
consecutive months for whatever reason, Landlord shall have the option to
require that, beginning with the first payment of rent due following the
imposition of the third consecutive late charge, rent shall no longer be paid
in monthly installments but shall be payable three (3) months in advance.


35.Mortgagee and Senior Lessor Protection.  No act or failure to act on the 
   --------------------------------------
part of Landlord which would entitle Tenant under the terms of this Lease, or
by law, to be relieved of Tenant's obligations hereunder or to terminate this
Lease, shall result in a release of such obligations or a termination of this
Lease unless (a) Tenant has given notice by registered or certified mail to
Landlord and to any beneficiary of a deed of trust or mortgage covering the
Building and to the lessor under any master or ground lease covering the
Building, the Site or any interest therein whose identity and address shall
have been furnished to Tenant, and (b) Tenant offers such beneficiary,
mortgagee or lessor a reasonable opportunity (but in no event less than thirty
(30) days) to cure the default, including time to obtain possession of the
Premises by power of sale or of judicial foreclosure, if such should prove
necessary to effect a cure. Landlord shall, from time to time, give Tenant
written notice of the identity and address of the beneficiary of any deed of
trust or mortgage covering the Building and/or the lessor under any master or
ground lease.
<PAGE>
 
36.Definition of Landlord.  The term "Landlord" as used in this Lease, so far 
   ----------------------
as covenants or obligations on the part of Landlord are concerned, shall be
limited to mean and include only the owner or owners, at the time in question,
of the fee title to, or a lessee's interest in a ground lease of the Site or
master lease of the Building. In the event of any transfer, assignment or
other conveyance or transfer of any such title or interest, Landlord herein
named (and in case of any subsequent transfers or conveyances, the then
grantor) shall be automatically freed and relieved from and after the date of
such transfer, assignment or conveyance of all liability with respect to the
performance of any covenants or obligation s on the part of Landlord contained
in this Lease thereafter to be performed and, without further agreement, the
transferee of such title or interest shall be deemed to have agreed to observe
and perform any and all obligations of Landlord hereunder, during its
ownership of the Premises. Landlord may transfer its interest in the Premises
without the consent of Tenant and such transfer or subsequent transfer shall
not be deemed a violation on Landlord's part of any of the terms and
conditions of this Lease.


37.Waiver.  The failure of Landlord or Tenant to seek redress for violation
   ------
of, or to insist upon strict performance of, any term, covenant or condition
of this Lease or the Rules and Regulations attached hereto as Exhibit "D",
                                                              -----------  
shall not be deemed a waiver of such violation or prevent a subsequent act
which would have originally constituted a violation from having all the force
and effect of an original violation, nor shall the failure of Landlord to
enforce any of said Rules and Regulations against any other tenant of the
Building be deemed a waiver of any such Rule or Regulation, nor shall any
custom or practice which may become established between the parties in the
administration of the terms hereof be deemed a waiver of, or in any way
affect, the right of either party to insist upon the performance by the other
in strict accordance with said terms. The subsequent acceptance or payment of
rent hereunder by Landlord or Tenant shall not be deemed to be a waiver of any
preceding breach by Tenant or Landlord of any term, covenant or condition of
this Lease, other than the failure of Tenant to pay the particular rent so
accepted, regardless of Landlord's knowledge of such preceding breach at the
time of acceptance of such rent.


38.Identification of Tenant.  Unless the provisions of Paragraph 52 herein
   ------------------------
below are applicable to this Lease, then if more than one person executes this
Lease as Tenant, (a) each of them is jointly and severally liable for the
keeping, observing and performing of all of the terms, covenants, conditions,
provisions and agreements of this Lease to be kept, observed and performed by
Tenant, and (b) the term "Tenant" as used in this Lease shall mean and include
each of them jointly and severally and the act of or notice from, or notice or
refund to, or the signature of, any one or more of them, with respect to the
tenancy or this Lease, including, but not limited to, any renewal, extension,
expiration, termination or modification of this Lease, shall be binding upon
each and all of the persons executing this Lease as Tenant with the same force
and effect as if each and all of them had so acted or so given or received
such notice or refund or so signed.


39.Year 2000.  Notwithstanding any covenant or provision contained in the Lease 
   ---------
to the contrary, Landlord shall have no liability or responsibility whatsoever
to Tenant for (i) any disruption or interruption in Tenant's business, (ii)
any disruption or interruption in Tenant's use or possession of the Premises,
or (iii) any other damage or consequence suffered or experienced by Tenant,
arising from or relating in any way to the malfunction, shut down or other
abnormal behavior of any computer or computer controlled system which provides
utilities or services to the Premises, or controls any systems serving the
Premises (whether such computer is within the control of Landlord or
otherwise) resulting 
<PAGE>
 
from the inability or failure of any such computer or computer controlled
system to recognize the year 2000, and distinguish said year from the year
1900 (sometimes referred to as the "Y2K problem", or the "failure to be year
2000 compliant"). In connection with the construction of the Landlord's Work
and the Tenant's Improvements, Landlord shall request that the Contractor (as
defined in the Work Letter) take such action as is commercially reasonable so
that the systems being installed are year 2000 compliant.


40.Terms and Headings.  The words "Landlord" and "Tenant" as used herein shall 
   ------------------
include the plural as well as the singular. Words used in any gender include
other genders. If there be more than one Tenant, i.e., if two or more persons
or entities are jointly referred to in this Lease as "Tenant," the obligations
hereunder imposed upon Tenant shall be joint and several. The Paragraph
headings of this Lease are not a part of this Lease and shall have no effect
upon the construction or interpretation of any part hereof.


41.Examination of Lease.  Submission of this instrument for examination or
   --------------------
signature by Tenant does not constitute a reservation of or option for Lease,
and it is not effective as a Lease or otherwise until execution by and
delivery to both Landlord and Tenant.


42.Time.  Time is of the essence with respect to the performance of every 
   ----
provision of this Lease in which time or performance is a factor. For purposes
of this Lease, the term "business day" shall refer to any day other than a
Saturday, Sunday or a legal holiday for national banks in the location where
the Building is located.


43.Prior Agreement; Amendments.  This Lease contains all of the agreements of 
   ---------------------------
the parties hereto with respect to any matter covered or mentioned in this
Lease, and no prior agreement or understanding, oral or written, express or
implied, pertaining to any such matter shall be effective for any purpose. No
provision of this Lease may be amended or added to except by an agreement in
writing signed by the parties hereto or their respective successors in
interest. The parties acknowledge that all prior agreements, representations
and negotiations are deemed superseded by the execution of this Lease to the
extent they are not incorporated herein.


44.Severability.  Any provision of this Lease which shall prove to be invalid,
   ------------
void or illegal in no way affects, impairs or invalidates any other provision
hereof, and such other provisions shall remain in full force and effect.


45.Recording.  Neither Landlord nor Tenant shall record this Lease nor a short
   ---------
memorandum thereof without the consent of the other and if such recording
occurs, it shall be at the sole cost and expense of the party requesting the
recording, including any documentary transfer taxes or other expenses related
to such recordation.


46.Limitation on Liability.  The obligations of Landlord under this Lease do
   -----------------------
not constitute personal obligations of the individual partners, directors,
officers, members or shareholders of Landlord, and Tenant shall not seek
recourse against the individual partners, directors, officers, members or
shareholders of Landlord or any of their personal assets for satisfaction of
any liability in respect to this Lease. In consideration of the benefits
accruing hereunder, Tenant and all successors and assigns covenant and agree
that in the event of any actual or alleged failure, breach or default
hereunder by Landlord, the sole 
<PAGE>
 
and exclusive remedy shall be against Landlord's interest in the Building in
the rental stream and sales proceeds thereof.


47.Riders.  Clauses, plats and riders, if any, signed by Landlord and Tenant
   ------
and affixed to this Lease are a part hereof.


48.Signs.  Tenant shall not place any sign upon the Premises or the Building
   -----
without Landlord's prior written consent which consent in the case of interior
signage within the Building, shall not be unreasonably withheld or delayed and
which consent, in the case of exterior signage with respect to the Building
(except as specifically provided in this Paragraph 48) may be given or
withheld by Landlord in its discretion. Tenant shall have the right to utilize
all Building signage space facing Townsend Street without any additional
compensation to Landlord. All signs shall be constructed, erected and affixed
to the Premises at Tenant's sole cost and expense, and Tenant shall be
responsible for the removal of such signage, and the repair of any damage to
the Building caused thereby, at the end of the Term. All signs shall be in
full compliance with all applicable ordinances, statutes and regulations
imposed by all applicable governmental authorities. Tenant shall have until
August 1, 2000 within which to notify Landlord in writing that Tenant wishes
to place Tenant's signage on the easterly and westerly facades of the
Building, in which case Tenant shall be allowed to do so at no charge during
the initial ten (10) year Term of this Lease. If Tenant fails to give Landlord
such notice within the time period provided, Landlord may lease such facades
to third parties as Landlord determines appropriate, without compensation to
Tenant. In no event, however, shall Landlord lease such facades to a
competitor of Tenant. During the Extended Terms, Landlord may impose a
reasonable signage rental fee, and adjust such fee periodically as Landlord
reasonably determines, based on the thencurrent rental value for comparable
signage, for the easterly and westerly Building facades. Tenant's rights to
utilize the Building facades for signage is limited to signage related to the
business of Tenant only (and in the event of an assignment or sublease
pursuant to the provisions of this Lease, the business of such assignee or
sublessee). Tenant shall have no right to sublet the signage space, nor
otherwise earn a profit therefrom. Following the full execution and delivery
of this Lease by both Landlord and Tenant, Tenant shall be entitled to place a
banner at the roof line on the exterior facade of the Building announcing the
intended occupancy of the Building by Tenant. The wording of such banner shall
be subject to reasonable review by Landlord. Any and all publicity or public
announcements of any kind with respect to the execution of this Lease or any
other matter relating to the Lease (exclusive of the banner described
immediately above) to be made by Tenant shall be subject to the prior written
consent of Landlord, which consent shall not be unreasonably withheld or
delayed.


49.Modification for Lender.  If in connection with obtaining construction,
   -----------------------
interim or permanent financing for the Building, the lender shall request
reasonable modifications in this Lease as a condition to such financing,
Tenant will not unreasonably withhold, delay or defer its consent thereto,
provided that such modifications do not increase the obligations of Tenant
hereunder or materially adversely affect the leasehold interest hereby created
or Tenant's rights hereunder, including Tenant's parking rights.


50.Accord and Satisfaction.  No payment by Tenant or receipt by Landlord of a
   -----------------------
lesser amount than the rent payment herein stipulated shall be deemed to be
other than on account of the rent, nor shall any endorsement or statement on
any check or any letter accompanying any check or payment as rent be deemed an
accord and satisfaction and Landlord may accept such check or payment without
prejudice to 
<PAGE>
 
Landlord's right to recover the balance of such rent or pursue any other
remedy provided in this Lease. Tenant agrees that each of the foregoing
covenants and agreements shall be applicable to any covenant or agreement
either expressly contained in this lease or imposed by any statute or at
common law.


51.Financial Statements.  At any time during the Term of this Lease, and if 
   --------------------
requested by Landlord in connection with a potential sale or financing of the
Building, Tenant shall, upon ten (10) days prior written notice from Landlord,
provide Landlord with a current financial statement and financial statements
of the two (2) years prior to the current financial statement year. Except in
connection with a request by Landlord in connection with a potential sale or
financing, Landlord shall limit its requests for financial statements to once
per calendar quarter. Such statements shall be prepared in accordance with
generally accepted accounting principles and, if such is the normal practice
of Tenant, shall be audited by an independent certified public accountant.
Landlord shall use commercially reasonable efforts to protect the
confidentiality of any such statement and to request that any proposed buyer
or lender similarly treat the information contained in such statement as being
confidential in nature, such that such information shall only be disclosed to
the consultants, analysts or counsel as may be reasonably necessary in order
to evaluate a potential purchase of, or loan upon, the Building.

     In connection with any and all financial statements to be delivered by
Tenant to Landlord, Landlord shall deal with Mr. Tony Attig, Executive Partner
and Chief Accounting Officer as the representative of Tenant and Tenant shall be
entitled to deal with and provide notices and copies of financial statements to
Douglas C. Rosenberg or any successor-in-interest, as from time to time,
designated by Landlord.  In the event that Mr. Attig no longer serves as
Tenant's representative, Tenant shall give written notice to Landlord of another
person or officer with which Landlord is to deal and, in the event of the
failure of Tenant to give such written notice to Landlord, Landlord shall be
entitled to deal with Tenant's facilities manager or any other officer or
manager of Tenant.


52.Tenant as Corporation.  If Tenant executes this Lease as a corporation,
   ---------------------
then Tenant and the persons executing this Lease on behalf of Tenant represent
and warrant that the individuals executing this Lease on Tenant's behalf are
duly authorized to execute and deliver this Lease on its behalf in accordance
with a duly adopted resolution of the board of directors of Tenant, a copy of
which is to be delivered to Landlord on execution hereof, and in accordance
with the By-Laws of Tenant and that this Lease is binding upon Tenant in
accordance with its terms.


53.No Partnership or Joint Venture.  Nothing in this Lease shall be deemed to 
   -------------------------------
constitute Landlord and Tenant as partners or joint venturers. It is the
express intent of the parties hereto that their relationship with regard to
this Lease be and remain that of landlord and tenant.


54.Rooftop Deck/Rooftop Antennae.
   -----------------------------

54.1 Subject to Landlord's prior approval of the plans and specifications, which
approval shall not be unreasonably withheld or delayed, Tenant shall have the
right to construct a roof deck on the Building.  Any such improvement to the
Building shall be done at Tenant's sole cost, by licensed, bonded contractors
approved by Landlord, and in strict compliance with all applicable rules,
regulations, ordinances and other requirements of every nature imposed by any
governmental authority with jurisdiction over the Building.  
<PAGE>
 
Tenant shall obtain all applicable permits and approvals as may also be
required for such construction.

54.2 Subject to Landlord's prior approval, Tenant may install, at Tenant's sole
cost, an antennae or satellite dish on the roof of the Building.  Any such
improvement to the Building shall be done at Tenant's sole cost, by licensed,
bonded contractors approved by Landlord, and in strict compliance with all
applicable rules, regulations, ordinances and other requirements of every nature
imposed by any governmental authority with jurisdiction over the Building.
Tenant shall obtain all applicable permits and approvals as may also be required
for such modifications.

55.Option to Lease.  Landlord shall employ reasonable effort (without cost to
   ---------------
Landlord) to obtain an option to lease for the benefit of Tenant in connection
with that certain real property commonly known as 420 Townsend Street, San
Francisco, California. Landlord shall consult with Tenant in connection with
its attempt to obtain such an option to lease and in connection with the terms
and conditions of any such option.

     If, during the Term of this Lease, Landlord purchases the real property
commonly known as 420 Townsend Street, San Francisco, California ("420
Property"), and provided that Tenant is not then in default, beyond any
applicable cure period, of this Lease, Landlord shall notify Tenant of such
purchase and for the first thirty (30) days following the close of escrow for
Landlord's purchase of such property, Tenant shall have the right to negotiate
with Landlord for the leasing of any space then unleased, unoccupied and
available in such property.  The right contained in this paragraph shall be
personal to Tenant (and/or any Permitted Transferee) and may be exercised only
by Tenant (and/or any Permitted Transferee) and only if the originally named
Tenant (or any Permitted Transferee) has not assigned this Lease or sublet at
any time during the Term more than all or any portion of two (2) floors of the
Premises.  In the event that Landlord and Tenant (or any Permitted Transferee)
have not executed a mutually acceptable lease for the applicable space at the
420 Property by the expiration of the thirty (30) day period described above,
then Tenant shall have no further rights under this paragraph or in connection
with the 420 Property including, but not limited to, any right to require that
Landlord negotiate further with Tenant or lease any space on any basis in  the
420 Property to Tenant.

56.Landlord's Representations.  Notwithstanding any provision to the contrary
   --------------------------
of this Lease, Landlord represents and warrants to Tenant that, to the best of
Landlord's knowledge: (i) the Premises, the Building and the Site as of the
date of this Lease are in compliance in all material respects with all laws
regarding Hazardous Materials ("Hazardous Materials Laws"). Landlord further
represents and warrants that, to the best of Landlord's knowledge, no
litigation has been filed or threatened, nor are any settlements pending with
any governmental or private party, concerning the actual or alleged presence
of Hazardous Materials in or on the Premises, Building or Site, nor has
Landlord received any written notice of any violation, or any alleged
violation, of any Hazardous Materials Laws, pending claims or pending
investigations with respect to the presence of Hazardous Materials on or in
the Premises, Building or Site. In addition to Landlord's indemnification of
Tenant pursuant to the provisions of Paragraph 7.2(b) above, except to the
extent that the Hazardous Material in question was released, emitted, used,
stored, manufactured, transported or discharged by Tenant or any of its
agents, employees, contractors or invitees, Tenant shall not be responsible
for and Tenant is hereby released from any claim, remediation obligation,
investigation obligation, removal obligation, monetary obligation, liability,
cause of action, penalty, 
<PAGE>
 
attorneys' fees, costs, expenses or damages owing or alleged to be owing to
any third party with respect to any Hazardous Materials present in or on the
Premises, the Building or the Site, or the soil, ground water or surface water
thereof, without regard to whether the Hazardous Materials were present in or
on the Premises, the Building or the Site as of the Lease Commencement Date or
whether the presence of the Hazardous Materials was caused by any person other
than Landlord. In no event, however, shall the indemnification obligations of
Landlord in connection with the Hazardous Materials be more expansive than the
indemnification obligation of Landlord as set forth in Paragraph 7.2(b) above.
Landlord's representations and warranties under this Paragraph 56 and
Landlord's indemnification obligation under Paragraph 7.2(b) shall survive
termination of this Lease.


57.Arbitration.  Any dispute pursuant to the provisions of Paragraph 3.2 which
   -----------
is not resolved pursuant to such Paragraph shall be finally settled by binding
arbitration in accordance with and under the rules of practice and procedure
for arbitration hearings of Judicial Arbitration and Mediation Services, Inc.
("JAMS"), or its successor in San Francisco, California. The parties may agree
upon a retired judge from the JAMS panel. If they are unable to agree, JAMS
shall provide a list of available judges containing one more judge than there
are parties to the arbitration and each party may strike one. The remaining
judge shall serve as the arbitrator. The arbitrator shall have the authority
to grant injunctive and/or other equitable relief. The arbitrator shall not
have the power to commit errors of law or legal reasoning and the appropriate
court shall have the authority to review the award for errors of fact, law or
legal reasoning. The award may also be vacated or corrected pursuant to the
California Code of Civil Procedure for any such error. If and when a demand
for arbitration is made by either party, the parties agree to execute a
submission agreement, provided by JAMS, setting forth the rights of the
parties and the rules and procedures to be followed at the arbitration
hearing; provided, however, that (i) the arbitration shall take place in San
Francisco California; (ii) the arbitrator shall apply the rules of evidence
and substantive law of the State of California; (iii) the arbitrator shall
render written findings of fact and conclusions of law; (iv) the parties shall
be entitled to conduct such pre-hearing discovery as would otherwise be
permitted under California law; (v) the arbitrator shall have the authority to
entertain and decide motions before the arbitration hearing as otherwise would
be permitted in a court of law, including, by way of example, motions to
compel discovery and motions for summary judgment; and (vi) remedies which the
arbitrator shall have the authority to grant shall be limited to the same
remedies which could otherwise be imposed by a court of law. Such arbitration
shall be the sole remedy available to the parties.


     IN WITNESS WHEREOF, the parties have executed and delivered this Lease on
the day and year first above written.


LANDLORD:                                       TENANT:
                                                
Rosenberg SOMA Investments II, LLC, a
 Delaware limited liability company
                                                USWeb Corporation, a
By:  TRC Investors II, LLC, a California        Delaware corporation
     limited liability company, Manager
                                                By: ___________________________
     By: The Rosenberg Company, a               Name: _________________________ 
<PAGE>
 
     California corporation, Manager            Its: __________________________
                                                
                                                           
     By:_____________________
        Douglas C. Rosenberg                    By: ___________________________
        President                               Name: _________________________
                                                Its: __________________________
     By:_____________________
        Douglas C. Rosenberg
        Secretary
<PAGE>
 
                                   EXHIBIT A

                                   FLOOR PLAN
                                   ----------


                                   [Attached]
<PAGE>
 
                                   EXHIBIT B
                                   ---------






                     LANDLORD'S NOTICE OF LEASE TERM DATES
                     -------------------------------------
                                        


     To:  USWeb Corporation, a Delaware corporation


     Date:  __________, 1999



     Re:  The Office Lease ("Lease") dated March _____, 1999 between USWeb
Corporation, a Delaware corporation, ("Tenant"), and Rosenberg SOMA Investments
II, LLC, a Delaware limited liability company, ("Landlord"), concerning that
certain premises (the "Premises") consisting of all four (4) floors of office
space, all of the basement parking garage and basement storage area located in
that certain building (the "Building") commonly known as 410 Townsend Street,
San Francisco, CA.

     In accordance with the Lease, Landlord and Tenant confirm as follows:

     1.   The Premises and the Building have been delivered to and accepted by
Tenant; Tenant acknowledges that all Tenant Improvements and other Landlord's
Work required under the Lease have been satisfactorily completed.

     2.   The Lease Commencement Date is _________, 1999; the Lease Expiration
Date is ___________, 2009.

     3.   Tenant's obligation to pay Aggregate Monthly Basic Rent under the
Lease shall commence on the Lease Commencement Date, as specified in Paragraph 2
above.

     4.   Aggregate Monthly Basic Rent and Operating Rent (when accrued pursuant
to Paragraph 5.3 of the Lease) are due and payable in advance on the first day
of each and every month during the Term of Lease.  All payments shall be made
payable to Landlord and
<PAGE>
 
delivered care of ROK Properties, Inc., 501 Second Street, Ste. 214, San
Francisco, CA 94107.



                              AGREED AND ACCEPTED
                              -------------------
                                        


LANDLORD:
                                                  TENANT:
Rosenberg SOMA Investments II, LLC, a 
 Delaware limited liability company               USWeb Corporation, a
                                                  Delaware corporation
By:  TRC Investors II, LLC, a California
     limited liability company, Manager           By: __________________________
                                                  Name: ________________________
                                                  Its: _________________________
     By:  The Rosenberg Company, a   
          California corporation, Manager         By: __________________________
                                                  Name: ________________________
          By:_____________________                Its:  ________________________
             Douglas C. Rosenberg
             President
 
          By:_____________________
             Douglas C. Rosenberg
             Secretary
 
<PAGE>
 
                                   EXHIBIT C
                                   ---------

                                 SAMPLE FORM OF
                                 --------------
                          TENANT ESTOPPEL CERTIFICATE
                          ---------------------------
                                        

The undersigned, ______________________________ ("Landlord"), with a mailing,
address c/o 
________________________________________________________________
and _____________________________ ("Tenant"), hereby certify to
_____________________, a ________________________ as follows:


     1.   Attached hereto is a true, correct and complete copy of that certain
          lease dated ___________________ between Landlord and Tenant (the
          "Lease"), which demises premises which are located on the second (2nd)
          floor of the Building located at ___________________.

          The Lease is now in full force and effect and has not been amended,
          modified or supplemented, except as set forth in Paragraph 4 below.


     2.   The term of the Lease commenced on _______________________.

     3.   The term of the Lease shall expire on _______________________.

     4.   The Lease has: (Initial one)

          ( ) not been amended, modified, supplemented, extended, renewed or
          assigned.

          ( ) been amended, modified, supplemented, extended, renewed or
          assigned by the following described agreements, copies of which are
          attached hereto:

          _________________________________________________________
          _________________________________________________________

     5.   Tenant has accepted, is now in possession of and is now conducting
          business in said Premises.

     6.   Tenant and Landlord acknowledge that the Lease will be assigned to and
          that no modification, adjustment, revision or cancellation of the
          Lease or amendments thereto shall be effective unless written consent
          of is obtained, and that until further notice, payments under the
          Lease may continue as heretofore.
<PAGE>
 
     7.   The amount of Basic Annual Rent is $____________
          Basic Annual Rent shall be increased based upon operating expense
          increases
          and as follows:
          _____________________________________.

     8.   The amount of security deposits (if any) is $ ____________
          No other security deposits have been made.

     9.   Tenant is paying the full lease rental, which has been paid in full as
          of the date hereof. No rent under the Lease has been paid for more
          than thirty (30) days in advance of its due date.

     10.  All Work required to be performed by Landlord under the Lease has been
          completed and all required contributions by Landlord to Tenant on
          account of Tenant Improvements have been received.

     11.  There are no defaults on the part of the Landlord or Tenant under the
          Lease.

     12.  Tenant has no defense as to its obligations under the Lease and claims
          no set-off or counterclaim against Landlord.

     13.  Tenant has no right to any concessions (rental or otherwise) or
          similar compensation in connection with renting the space it occupies,
          except as provided in the Lease.

     14.  The Lease, amended as noted in Item 4 above, represents the entire
          agreement between Landlord and Tenant as to this leasing.


          All provisions of the Lease and the amendments thereto (if any)
referred to above are hereby ratified.

DATED: _______________________ , 19__
TENANT:                         LANDLORD:
------                          --------

___________________________,    __________________________,
a _________________________     a _________________________


By:______________________     By:__________________________
Name:___________________      Name:_______________________
Its:______________________    Its:__________________________
<PAGE>
 
                                   EXHIBIT D
                                   ---------

                              RULES & REGULATIONS
                              -------------------



1.          Subject to Paragraph 48 of the Lease, no sign, placard, picture,
advertisement, name or notice shall be installed or displayed on any part of the
outside or inside of the Building without the prior written consent of Landlord,
which shall not be unreasonably withheld or delayed. Landlord shall have the
right to remove, at Tenant's expense and without notice, any sign installed or
displayed in violation of this rule. All approved signs or lettering on doors,
windows and walls shall be printed, painted, affixed or inscribed at the expense
of Tenant by a person reasonably approved by Landlord, using materials, style
and format reasonably acceptable to Landlord.

2.          Landlord shall have the right to approve the window coverings in all
exterior and atrium window offices of the Premises, which approval shall not be
unreasonably withheld or delayed. No awning shall be permitted on any part of
the Premises. Tenant shall not place anything against or near glass partitions
or doors or windows which may appear unsightly from outside the Premises.

3.          Tenant shall not obstruct any sidewalks, halls passages, exits,
entrances, elevators or stairways of the Building in a manner which would
violate any applicable code or ordinance.

4.          Landlord will furnish Tenant, free of charge, with 10 keys to each
door lock in the Premises and 60 parking garage entry cards. Landlord may make a
reasonable charge for any additional keys or parking entry cards. Tenant shall
not make or have made additional keys or cards without Landlord's prior consent.
Tenant may install a security system at the Premises at Tenant's expense, in
which event Tenant shall provide Landlord with a key and/or entry card for
purposes of Landlord's entry to the Premises as provided in the Lease.  Tenant,
upon the termination of its tenancy, shall deliver to Landlord the keys for all
doors and all parking cards which have been furnished to Tenant, and in the
event of loss of any keys or card keys so furnished, shall pay Landlord
therefor.

5.          If Tenant requires telegraphic, telephonic, burglar alarm or similar
services, it shall first obtain, and comply with, Landlord's reasonable
instructions in their installation.

6.          No equipment, materials, furniture, packages, supplies,
merchandise or other property will be received in the Building or carried in
the elevators except between such hours and in such elevators as may be
designated by Landlord.

7.          Tenant shall not place a load upon any floor of the Premises which
exceeds the load per square foot which such floor was designed to carry and
which is allowed by 
<PAGE>
 
law. Landlord shall have the right to prescribe the weight, size and position
of all equipment, materials, furniture or other property brought into the
Building. Heavy objects, if such objects are considered necessary by Tenant,
as reasonably determined by Landlord, shall stand on such platforms as
determined by Landlord to be necessary to properly distribute the weight. The
persons employed to move such equipment in or out of the Building must be
reasonably acceptable to Landlord. Landlord will not be responsible for loss
of, or damage to, any such equipment or other property from any cause, and all
damage done to the Building by maintaining or moving such equipment or other
property shall be repaired at the expense of Tenant.

8.          Tenant shall not use or keep in the Premises any kerosene,
gasoline or inflammable or combustible fluid or material other than those
limited quantities necessary for the operation or maintenance of office
equipment. Tenant shall not use or permit to be used in the Premises any foul
or noxious gas or substance, or permit or allow the Premises to be occupied or
used in an unlawful manner by reason of noise, odors or vibrations, nor shall
Tenant bring into or keep in or about the Premises any birds or animals,
except animals assisting disabled persons.

9.          Tenant shall not use any method of heating or air conditioning
other than that reasonably approved by Landlord. No space heaters of any type
are to be used within the Premises. Landlord reserves the right to remove
space heaters found during normal inspection of Premises.

10.         Heat and air conditioning shall be provided as set forth in the
Lease.

11.         Landlord reserves the right, exercisable without notice and without
liability to Tenant, to change the name and street address of the Building.

12.         Landlord reserves the right to exclude from the building between
the hours of 6:00 p.m. and 7:00 a m. the following day, or such other hours as
may be established from time to time by Landlord, and on Saturdays, Sundays
and legal holidays, any person unless that person is known to the person or
employee in charge of the Building and has a pass or is properly identified.
Tenant shall be responsible for all persons for whom it requests passes and
shall be liable to Landlord for all acts of such persons. Landlord shall not
be liable for damages for any error with regard to the admission to or
exclusion from the Building of any person. Landlord reserves the right to
prevent access to the Building in case of invasion, mob, riot, public
excitement or other commotion by closing the doors or by other appropriate
action.

13.         Tenant shall close and lock the doors of its Premises and entirely
shut off all water faucets or other water apparatus, and, except with regard to
Tenant's computers and other equipment which requires utilities on a twenty-four
hour basis, all electricity, gas or air outlets before Tenant and its employees
leave the Premises. Tenant shall be responsible for any damage or injuries
sustained by Landlord for noncompliance with this rule.
<PAGE>
 
14.         The toilet rooms, toilets, urinals, wash bowls and other apparatus
shall not be used for any purpose other than that for which they were
constructed and no foreign substance of any kind whatsoever shall be thrown
therein. The expense of any breakage, stoppage or damage resulting from the
violation of this rule shall be borne by the Tenant who, or whose employees or
invitees, shall have caused it.

15.         Tenant shall not sell, or permit the sale at retail, of newspapers,
magazines, periodicals, theater tickets or any other goods or merchandise to the
general public in or on the Premises.  Tenant shall not use the Premises for any
business or activity other than that specifically provided for in Tenant's
Lease.

16.         Tenant shall not mark, drive nails, screw or drill into the
partitions, woodwork or plaster or in any way deface the Premises or any part
thereof, except to install normal wall hangings, and to secure files and
bookcases and other furniture that could fall over. Landlord reserves the right
to direct electricians as to where and how telephone and telegraph wires are to
be introduced to the Premises. Tenant shall not cut or bore holes for wires.
Tenant shall not affix any floor covering to the floor of the Premises in any
manner except as reasonably approved by Landlord. Tenant shall repair any damage
resulting from noncompliance with this rule.

17.         Tenant shall not install, maintain or operate upon the Premises any
vending machine without the written consent of Landlord.

18.         Landlord reserves the right to exclude or expel from the Building
any person who, in Landlord's reasonable judgment, is intoxicated or under the
influence of liquor or drugs or who is in violation of any of the Rules and
Regulations of the Building.

19.         Tenant shall not place in any trash box or receptacle any material
which cannot be disposed of in the ordinary and customary manner of trash and
garbage disposal. All garbage and refuse storage and disposal shall be made in
accordance with directions issued from time to time by Landlord.

20.         The Premises shall not be used for the storage of merchandise held
for sale to the general public, or for lodging or for manufacturing of any
kind, nor shall the Premises be used for any improper, immoral or
objectionable purpose. No cooking shall be done or permitted by any tenant on
the Premises, except that use by tenant of Underwriters' Laboratory-approved
equipment for brewing coffee, tea, hot chocolate and similar beverages shall
be permitted, and the use of a microwave oven shall be permitted, provided
that such equipment and use is in accordance with all applicable federal,
state, county and city laws, codes, ordinances, rules and regulations.

21.         Except for mail carts and hand trucks, Tenant shall not bring any
vehicles of any kind into the Building except the Garage.  Tenant shall comply
with all reasonable rules and regulations with respect to the use of the Garage
as Landlord may from time to time deliver to Tenant in writing.
<PAGE>
 
22.         Without the written consent of Landlord, Tenant shall not use the
name of the Building in connection with or in promoting or advertising the
business of Tenant except as Tenant's address.

23.         Tenant shall comply with all safety, fire protection and evacuation
procedures and regulations established by any governmental agency or reasonably
established by Landlord.

24.         Tenant assumes any and all responsibility for protecting its
Premises from theft, robbery and pilferage, which includes keeping doors
locked and other means of entry to the Premises closed.

25.         The requirements of Tenant will be attended to only upon
appropriate application to the office of the Building by an authorized
individual. Employees of Landlord shall not perform any work or do anything
outside of their regular duties unless under special instructions from
Landlord, and no employee of Landlord will admit any person (tenant or
otherwise) to any office without specific instructions from Landlord.

26.         Landlord may waive any one or more of these Rules and Regulations
for the benefit of Tenant, but no such waiver by Landlord shall be construed
as a permanent or continuing waiver of such Rules and Regulations in favor of
Tenant, nor prevent Landlord from thereafter enforcing any such Rules and
Regulations against Tenant.

27.         These Rules and Regulations are in addition to the terms,
covenants, agreements and conditions of the Lease. In the event these Rules
and Regulations conflict with any provision of the Lease, the Lease shall
control.

28.         Landlord reserves the right to make such other and reasonable Rules
and Regulations as, in its judgment, may from time to time be needed for safety
and security, for care and cleanliness of the Building and for the preservation
of good order therein, provided such rules and regulations do not materially
increase Tenant's obligation hereunder or diminish Tenant's rights hereunder.
Tenant agrees to abide by all such Rules and Regulations hereinabove stated and
any additional rules and regulations which are adopted.

29.         Tenant shall be responsible for the observance of all of the
foregoing rules by Tenant's employees, agents, clients, customers, invitees
and guests.

30.         Smoking is prohibited in all enclosed areas of the Building without
limitation.  When smoking outside the Building, ash receptacles must be used and
provided by the smoker if not provided by Landlord. Smokers must not leave any
ashtrays, smoking material or debris in the area where they have been smoking,
except in ash receptacles.
<PAGE>
 
                                   EXHIBIT E
                                   ---------

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



               410 TOWNSEND STREET, SAN FRANCISCO, CALIFORNIA

                             TENANT WORK LETTER


     This Tenant Work Letter ("Work Letter") is entered into effective March 5,
1999, and shall set forth the terms and conditions controlling the construction
of the Premises.  Unless otherwise defined herein, all capitalized terms shall
have the meanings ascribed to them in that certain lease between USWeb
Corporation, a Delaware corporation ("Tenant") and Rosenberg SOMA Investments
II, LLC, a Delaware limited liability company ("Landlord") dated March 5, 1999
(the "Lease").


                                  SECTION 1
                           SELECTION OF CONTRACTOR


1.1.      Selection of General Contractor.  Tenant acknowledges and agrees that
          -------------------------------                                      
     Landlord shall  engage Cannon Constructors ("Contractor") to act as the
     general contractor for construction of all Landlord's Work (as defined
     below) and the Tenant's Improvements (as defined below) to be performed to
     the Building.  Landlord shall enter into one or more contracts with
     Contractor for the construction of Landlord's Work and the Tenant's
     Improvements (sometimes referred to collectively as the "Improvement
     Work").  The one or more contracts between Landlord and Contractor with
     respect to the Improvement Work shall separately reference and describe the
     Landlord's Work and the Tenant's Improvements and shall, in addition,
     separately reference the costs and charges attributable to the Landlord's
     Work and the Tenant's Improvements.  Landlord shall use commercially
     reasonable efforts to cause the Improvement Work to be substantially
     completed not later than July 7, 1999.  It is acknowledged, that
     substantial completion of the Tenant's Improvements is dependant, in part,
     on the timely performance by Landlord of those matters required of Landlord
     in connection with construction of the Tenant's Improvements and on the
     timely performance  by Tenant of those matters required by Tenant in
     connection with  construction of the Tenant's Improvements, including
     without limitation, those certain Tenant Benchmarks as defined and set
     forth in Paragraph 5.2 below.  Tenant's failure to meet a Tenant Benchmark
     shall constitute a Tenant Delay and shall be subject to Paragraph 3.2 of
     the Lease.  For purposes of the Lease and this Work Letter, "substantial
     completion" of the Improvement Work shall mean the date on which all of the
     following have occurred: (i) Landlord has substantially completed the
     Improvement Work in accordance with this Work Letter, as certified by
     Landlord's Architect (as defined below) subject only to completion of punch
     list items and such other items as do not materially affect the ability of
     Tenant to occupy and use the Premises; and (ii) Landlord has obtained all
     governmental approvals and occupancy certificates required for the legal
     occupancy of the Building.  Upon substantial completion of the Improvement
     
<PAGE>
 
     Work, Landlord shall give written notice thereof to Tenant.  Within three
     (3) business days after Tenant's receipt of such written notice, a
     representative of Tenant, a representative of Landlord and Tenant's
     Architect (as defined below) and Landlord's Architect shall conduct a
     physical inspection and walk through of the Premises for the purpose of
     determining which components of the Improvement Work, if any, have not been
     completed, and which require additional work or repair.  Within three (3)
     business days thereafter, Tenant's Architect and Landlord's Architect shall
     prepare a punch list setting forth such components of the Improvement Work.
     Landlord shall thereafter diligently pursue completion and/or repair of the
     punch list items.  Upon completion of all such punch list items, Landlord
     shall be considered to have completely fulfilled its obligations in
     connection with the Improvement Work subject to the provisions of Paragraph
     12 of the Lease.  Notwithstanding any provision to the contrary contained
     in the Lease or in this Work Letter, Tenant's acceptance of the Improvement
     Work or submission of a "punch list" with respect to Improvement Work shall
     not be deemed a waiver of Tenant's right to have latent defects in
     Improvement Work repaired at no cost to Tenant.  Tenant shall give written
     notice to Landlord whenever any such defect becomes reasonably apparent and
     Landlord shall repair such defect as soon as practicable so long as Tenant
     gives such notice to Landlord within one (1) year following substantial
     completion of the Improvement Work (as defined in Section 1.1).
     Notwithstanding the above provisions, Landlord shall have no obligation to
     repair any defect in the Tenant Improvements  resulting from or relating to
     design defects attributable to Tenant's Architect or any one or more of
     Tenant's Engineers (as defined below).  Subsequent to one (1) year
     following substantial completion of the Improvement Work, the repair
     obligation of Landlord with respect to latent defects shall be as otherwise
     set forth in the Lease.


1.2.      General Contractor's Contract for Improvements.  As a condition of
          ----------------------------------------------
     Contractor's contract with Landlord for the construction of the Tenant's
     Improvements (the "Construction Contract"), Contractor shall solicit and
     employ commercially reasonable effort to obtain bids from a minimum of
     three (3) subcontractors for each component of work contemplated by the
     Construction Drawings (as defined below)  to be performed pursuant to
     subcontract.  Contractor shall provide Landlord and Tenant with a copy of
     all such bids related to the Tenant's Improvements.  Contractor shall also
     provide Landlord and Tenant with an itemized breakdown of all general
     conditions proposed under the Construction Contract related to the Tenant's
     Improvements.  All general conditions shall be subject to Landlord's
     approval and to Tenant's approval as provided below in this paragraph.
     Contractor shall be limited to three and one-half percent (3 1/2 %) of the
     total cost of construction of the Tenant's Improvements incurred by
     Contractor as Contractor's profit in connection with construction of the
     Tenant's Improvements.  The proposed form of Construction Contract  shall
     set forth the cost of construction for Tenant's Improvements (either on
     fixed basis or on  a guaranteed maximum basis) and relate to the
     construction of the Tenant's Improvements in accordance with the
     Construction Drawings.  A copy of the proposed form of 
<PAGE>
 
     Construction Contract shall be delivered by Landlord to Tenant. Within
     five (5) business days following delivery by Landlord to Tenant of (i) a
     copy of the proposed form of Construction Contract; (ii) a copy of all
     bids of subcontractors in connection with the Construction Contract; and
     (iii) an itemized breakdown of the general conditions proposed in the
     Construction Contract, Tenant shall deliver written approval or
     disapproval of all such items to Landlord. If Tenant disapproves any such
     items, Tenant's notice to Landlord shall specify the basis for the
     disapproval. In the event that Tenant approves all of such items,
     Landlord shall proceed with construction of the Tenant's Improvements in
     accordance with the Construction Contract as so approved. In the event
     that Tenant disapproves any such items, Landlord shall reasonably attempt
     to satisfy any such objections of Tenant and shall give Tenant written
     notice of suggested resolutions which in each case Tenant shall approve
     or disapprove in writing within one (1) business day after receipt.
     Landlord may elect not to proceed with construction of the Tenant's
     Improvements pursuant to the Construction Contract until all objections
     as raised by Tenant have been fully satisfied and Tenant has given
     written approval of the Construction Contract in full, including without
     limitation all of the above described items. In the alternative, Landlord
     shall be entitled to proceed with construction of the Tenant's
     Improvements pursuant to the Construction Contract even if Tenant's final
     approval to all components of the Construction Contract has not yet been
     obtained provided that Landlord gives written notice to Tenant of its
     intent to so proceed and Tenant fails to object to such notice within two
     (2) business days following receipt by giving written notice to Landlord
     of such objection.



                                   SECTION 2
                                LANDLORD'S WORK


2.1.      Scope of Landlord's Work.  The following work and improvements 
          ------------------------                                              
     ("Landlord's Work") shall be specified in construction drawings prepared
     by Landlord's Architect ("Landlord's Drawings") and shall be constructed
     at Landlord's sole cost. Prior to Landlord's entry into the Construction
     Contract for construction of the Tenant's Improvements, Landlord shall
     provide Tenant with a copy of Landlord's Drawings. Landlord shall not be
     required to enter into the Construction Contract for the construction of
     the Tenant's Improvements until and unless Tenant has given written
     approval of Landlord's Drawings. The Landlord's Drawings shall set forth
     the scope of the Landlord's Work and shall include, but not be limited
     to, the improvements set forth below.

     2.1.1.     Installation of the primary heating, ventilating, and
           airconditioning system ("HVAC") for the Building, stubbed out to
           each floor, ready for local distribution.

     2.1.2.     Installation of 480 volt, 3 phase electrical power supply to
           the main power panel for the Building, and distribution thereof to
           subpanels on each floor of the Building as specified in the
           Construction Drawings.
<PAGE>
 
     2.1.3.     Installation of lifesafety systems as required by applicable
           building codes on an unimproved basis, including all sprinkler
           systems, emergency exit systems (including required lighting and
           signage) and other required fire safety systems.

     2.1.4.     Installation of the main telephone terminal panel with
           appropriately sized services in the telephone/electrical room
           specified in the Construction Drawings, and installation of
           telephone closets on each floor of the Building, ready for
           secondary line branching throughout each floor.

     2.1.5.     Construction of Men's and Women's restrooms on each floor of
           the Building, as specified in the Landlord's Drawings, with the
           exception of the basement.

     2.1.6.     Construction of gated basement parking and installation of a
           card key access system.

     2.1.7.     Installation of two (2) new passenger elevators serving all
           floors, as specified in the Landlord's Drawings.

     2.1.8.     Installation of operable windows throughout the Building in
           all current window opening locations.

     2.1.9.     Performance of all work necessary for the Building to comply
           with all applicable seismic regulations, the Americans with
           Disabilities Act of 1980 (except with respect to those compliances
           associated exclusively with the Tenant's Improvements) and all
           applicable path of travel regulations.

     2.1.10.    Installation of at least one (1) fiber optic system to a
           location in the Building mutually agreed upon by Landlord, Tenant
           and the fiber optic provider, ready for distribution throughout the
           Building.



                                   SECTION 3
                             TENANT'S IMPROVEMENTS


3.1.      Scope of Tenant's Improvements.  The physical improvements to the
          ------------------------------
     Premises and the Building (in addition to Landlord's Work) set forth and
     described in the Construction Drawings shall constitute the "Tenant's
     Improvements". For purposes of this Work Letter, the "Tenant Improvement
     Allowance Items" shall consist of the following: (i) all costs incurred
     in connection with or arising from the Construction Contract; (ii) all
     fees and costs of Tenant's Architect and Tenant's Engineers (as defined
     below); (iii) all space planning costs (subject to the limitations of
     paragraph 3.4); (iv) the cost of Tenant's security system to be installed
     at the Premises; (v) Landlord's 
<PAGE>
 
     supervision/construction management fee (as described in Paragraph 4.3
     below); (vi) all costs related to obtaining all necessary construction
     and other permits necessary for construction of the Tenant's
     Improvements; (vii) all fees and costs associated with the hiring of an
     expediter to assist in obtaining all building and planning department
     consents and approvals with respect to the Tenant's Improvements; (viii)
     the cost of other items related to the design and construction of the
     Tenant's Improvements; and (ix) all other costs and expenses incurred in
     connection with the Construction Contract or construction of the Tenant's
     Improvements. Tenant shall be responsible for the full amount of all such
     costs in connection with the Tenant's Improvements, all of which shall be
     paid in accordance with the provisions of this Work Letter.
     Notwithstanding anything to the contrary contained in the Lease or this
     Work Letter, the cost of the Tenant's Improvements and the Tenant
     Improvement Allowance Items shall not include (and Tenant shall have no
     responsibility for) the following components: (i) costs attributable to
     Landlord's Work or improvements installed "off-site" (such as streets,
     curbs, gutters, traffic lights, lights for parking and street lighting);
     (ii) costs incurred to remove hazardous materials from the Building
     unless the presence of such materials was caused by Tenant or its agents,
     contractors, employees or invitees in violation of hazardous materials
     laws (as such may exist from time to time); (iii) attorneys' fees
     incurred in connection with the Construction Contract (or any
     subcontracts), or attorneys' fees, experts' fees and other costs of legal
     and arbitration proceedings to resolve construction disputes with third
     parties except for attorney's fees and other costs incurred in connection
     with construction disputes relating to or arising out of decisions made,
     actions taken or positions taken by Tenant's Architect; (iv) loan fees,
     mortgage brokerage fees, interest and other costs of financing
     construction costs; (v) costs incurred as a consequence of a delay by
     Landlord or construction defects except for construction defects arising
     or relating in whole or in part to services provided or decisions made by
     Tenant's Architect or any other consultant or contractor engaged by
     Tenant; (vi) restoration costs in excess of insurance proceeds as a
     consequence of a casualty during construction, unless the casualty is
     caused by Tenant, its agents, contractors, employees or invitees; (vii)
     costs recovered by Landlord by reason of warranties or insurance; and
     (viii) penalties and late charges attributable to the failure to pay
     construction costs in accordance with the Construction Contract, except
     to the extent such penalties and late charges arise due to delays caused
     by Tenant, its agents, contractors, employees or invitees including,
     without limitation, Tenant's Architect.

3.2.      Tenant Improvement Allowance.  Tenant shall be entitled to a onetime
          ----------------------------
     tenant improvement allowance (the "Tenant Improvement Allowance") in the
     amount of Thirty-One and 50/100 Dollars ($31.50) per rentable square foot
     of the Premises as set forth in Paragraph 1.4 of the Lease. For purposes
     of calculation of the total Tenant Improvement Allowance, the maximum
     amount of the Improvement Loan (as defined below) and Landlord's
     obligation to advance space planning costs, the rentable square feet of
     the Premises shall be as set forth in Paragraph 1.4 of the Lease. The
     Tenant Improvement Allowance shall be 
<PAGE>
 
     exclusively applied toward the costs of completing the Tenant's
     Improvements. Landlord shall be entitled to employ the Tenant's
     Improvement Allowance in connection with payment of the Tenant
     Improvement Allowance Items. In no event shall Landlord be obligated to
     make disbursements pursuant to this Work Letter, or otherwise for the
     construction of the Tenant's Improvements, in excess of the Tenant
     Improvement Allowance, except as provided in Paragraph 3.3. Tenant shall
     be solely responsible for all costs incurred in constructing the Tenant's
     Improvements in excess of the Tenant Improvement Allowance, whether
     resulting from cost overruns, changes to the Construction Drawings or
     otherwise.

3.3.      Additional Funds for Tenant's Improvements.  Notwithstanding the 
          ------------------------------------------                            
     limitation on the Tenant Improvement Allowance to be provided by Landlord
     in the immediately preceding Paragraph, Tenant may request that Landlord
     loan Tenant additional funds (the "Improvement Loan") to be used to
     complete the Tenant's Improvements, if reasonably necessary, in the event
     the Tenant Improvement Allowance is insufficient to pay in full the cost
     of the Tenant's Improvements, taking into account any changes to the
     Construction Drawings made by Tenant (which shall be at Tenant's sole
     cost). In the event that the Tenant Improvement Allowance is insufficient
     as described above, Landlord shall loan to Tenant an additional amount
     not to exceed Three and 50/100 Dollars ($3.50) per rentable square foot
     of the Premises. The obligation of Landlord to make the Improvement Loan
     shall be conditioned on (i) exhaustion of the Tenant Improvement
     Allowance in connection with Tenant Improvement Allowance Items, (ii)
     Tenant contributing an amount equal to the Improvement Loan ("Matching
     Funds") and (iii) the Improvement Loan and Matching Funds being applied
     only towards hard construction costs as set forth in the Construction
     Contract. If, at the time the Construction Contract is approved by
     Tenant, the costs of the Tenant Improvement Allowance Items are
     reasonably anticipated to be in excess of the Tenant Improvement
     Allowance, then as a condition to Landlord's obligation to execute the
     Construction Contract, Tenant shall fund the full amount of the
     reasonably anticipated Matching Funds to Landlord as provided below. The
     amount of the Improvement Loan shall be evidenced by an installment
     promissory note (the "Note") made by Tenant in favor of Landlord in a
     form reasonably acceptable to Landlord and Tenant. The Note shall provide
     for interest at the rate of nine percent (9%) per annum, for a term of
     ten (10) years commencing as of the Lease Commencement Date and for equal
     monthly installment payments of principal and interest due on the first
     day of each calendar month, which payments shall be sufficient to fully
     amortize the principal amount of the Improvement Loan over the ten (10)
     year term of the Note. In the event that at the time the Construction
     Contract is finally approved by Tenant, it is not anticipated that any
     amount in excess of the Tenant Improvement Allowance will be required in
     connection with the cost of the Tenant Improvements, then to the extent
     that excess costs are thereafter incurred, Landlord shall be required to
     make the Improvement Loan in the maximum amount as described above,
     subject however, to the conditions provided in Clauses (i), (ii) and
     (iii) above. In connection with any such excess costs anticipated to be
     incurred and the 
<PAGE>
 
     requirement for Matching Funds or additional Matching Funds to be
     contributed by Tenant, such funds shall be deposited with Landlord as
     described below.


     Tenant shall solely be responsible for bearing the cost of the Tenant's
Improvements in excess of the Tenant Improvement Allowance and the Improvement
Loan.  In the event it becomes reasonably apparent from the Construction
Drawings and Construction Contract that the cost of the Tenant's Improvements
will exceed the Tenant Improvement Allowance, the Improvement Loan and the
Matching Funds, within ten (10) business days following final approval of the
Construction Contract by Tenant, Tenant shall deposit with Landlord (to be held
in an interest bearing account by Landlord) an amount equal to the cost of the
Tenant's Improvements in excess of the Tenant Improvement Allowance, the
Improvement Loan and the Matching Funds as reasonably determined by Landlord.
Tenant shall, in addition, within ten (10) business days following final
approval of the Construction Contract, deposit the Matching Funds with Landlord
to be held in an interest bearing account by Landlord.  The amount so deposited
by Tenant ("Tenant's Funds") shall be disbursed and/or employed in accordance
with Paragraph 3.5 below; provided however, that Tenant's Funds shall not be
used or applied towards the cost of completing the Tenant's Improvements until
such time as the Tenant Improvement Allowance has been exhausted in accordance
with the provisions of this Work Letter.  In the event that following final
approval of the Construction Contract by Tenant, additional funds are required
by reason of additional costs attributable to change orders or other reasons
approved by Tenant (or Tenant's Architect), which approval shall not be
unreasonably withheld or delayed, Landlord may, thereafter, from time to time
upon written notice to Tenant, require that Tenant deposit additional funds with
Landlord (within ten (10) business days following receipt by Tenant of the
request for an additional deposit) to be held by Landlord in an interest bearing
account as a part of the Tenant's Funds in an amount as reasonably determined by
Landlord equal to such excess amount of costs to be incurred in connection with
construction of the Tenant's Improvements.  Any and all interest accruing on the
Tenant's Funds shall accrue for the benefit of Tenant.  In the event that Tenant
fails to deposit additional funds with Landlord within ten (10) business days
following receipt by Tenant of the request for an additional deposit as
described above, then Landlord may, at the sole option of Landlord, but without
any requirement to do so, draw down from the cash portion of the security
deposit made by Tenant pursuant to the provisions of Paragraph 6.1 of the Lease
the amount of additional deposit requested by Landlord which Tenant has failed
to timely make.  In the event of any such withdrawal by Landlord, the funds so
withdrawn shall be held by Landlord as a portion of the Tenant's Funds and
disbursed by Landlord as otherwise provided herein.  Further, in the event of
any draw by Landlord against the cash portion of the security deposit, Tenant
shall be obligated to restore such drawn amount to the security deposit within
ten (10) days after receipt of written demand of Landlord requiring such
restoration in accordance with the provisions of Paragraph 6.1 of the Lease.
Within ten (10) business days following completion of construction of the
Tenant's Improvements and payment in full of all costs incurred by Landlord in
connection with such construction, any Tenant's Funds then held by Landlord,
together with any accrued interest then held, shall be disbursed by Landlord to
Tenant.
<PAGE>
 
3.4.      Cost of Initial Space Planning.  In connection with the Tenant's
          ------------------------------
     Improvements, Landlord shall advance the cost of initial space planning for
     the Premises up to the maximum amount of Ten Cents ($0.10) per rentable
     square foot of the Premises, which amount actually advanced by Landlord
     shall be debited against the Tenant Improvement Allowance otherwise
     available.


3.5.      Landlord's Disbursement Process.  During the construction of the
          -------------------------------
     Tenant's Improvements, Landlord shall make monthly disbursements of the
     Tenant Improvement Allowance (and to the extent necessary, the
     Improvement Loan, the Matching Funds and Tenant's Funds) for Tenant
     Improvement Allowance Items for the benefit of Tenant and shall authorize
     the release of monies for the benefit of Tenant as follows:


     3.5.1.     Monthly Disbursements.  On or before the first day of each 
                ---------------------
           calendar month during the construction of the Tenant's Improvements
           (or such other date as Landlord may designate), and before Landlord
           shall be required to disburse any funds hereunder, Contractor shall
           deliver to Landlord: (i) a request for payment of Contractor (and
           others as appropriate), approved by Tenant's Architect (which
           approval shall not be unreasonably withheld or delayed), in a form
           to be provided by Landlord, showing the schedule, by trade, of
           percentage of completion of the Tenant's Improvements in the
           Building, detailing the portion of the work completed and the
           portion not completed; (ii) invoices from Contractor (and others as
           appropriate), for labor rendered and materials delivered to the
           Building; (iii) executed mechanic's lien releases from Contractor
           (and all others requesting payment) which shall comply with the
           appropriate provisions, as reasonably determined by Landlord, of
           California Civil Code Section 3262(d); and (iv) all other
           information reasonably requested by Landlord. Tenant's Architect's
           approval of any request for payment shall be deemed Tenant's
           acceptance and approval of the work furnished and/or the materials
           supplied as set forth in the subject payment request. Tenant's
           Architect shall approve or disapprove any request for payment
           within three (3) business days following receipt of Tenant's
           Architect of such request and, in connection with any disapproval
           of the request, shall specifically state the reason for
           disapproval. In connection with any disapproval, Tenant's Architect
           shall, thereafter, respond within one (2) business days following
           receipt by Tenant's Architect of any revised request for payment.
           Within five (5) business days following written approval by
           Tenant's Architect, Landlord shall deliver a check made payable to
           Contractor (or other party as appropriate) in payment of: (A)
           amounts so requested by Contractor, as set forth in this Paragraph,
           less a retention in accordance with the provisions of the
           Construction Contract (the aggregate amount of such retentions to
           be known as the "Final Retention"), provided that Landlord does not
           dispute any request for payment based on noncompliance of any work
           with the approved Construction Drawings, or due to any substandard
           work, or for any other reason. Landlord's payment of such amounts
           shall not be deemed Landlord's approval or acceptance of the work
<PAGE>
 
           furnished or materials supplied as set forth in the subject payment
           request. In addition to the disbursement described immediately
           above, Landlord shall be entitled to disburse funds in payment of
           obligations incurred by Landlord for Tenant Improvement Allowance
           Items as Landlord may, from time to time, deem appropriate.
           Landlord shall provide to Tenant and Tenant's Architect, copies of
           invoices in connection with any such disbursements within five (5)
           business days following disbursement. Tenant shall, in addition, be
           entitle to submit, from time to time, invoices of Tenant's
           Architect and Tenant's Engineers, which invoices shall be approved
           by Tenant. Landlord shall pay such invoices as approved by Tenant
           within thirty (30) days following receipt by Landlord of approved
           invoices, but no more often than once per calendar month.


           In no event shall Landlord have any obligation to make
disbursements in excess of the aggregate of; (i) the Tenant Improvement
Allowance, (ii) the Improvement Loan, (iii) the Matching Funds as having been
deposited by Tenant with Landlord, and (iv) the Tenant's Funds as having been
deposited by Tenant with Landlord (exclusive of Matching Funds).

     3.5.2.     Final Retention.  Subject to the provisions of this Work
                ---------------
           Letter, a check for the Final Retention payable to Contractor shall
           be delivered by Landlord to Contractor following the completion of
           construction of the Tenant's Improvements, provided that (i)
           Contractor delivers to Landlord properly executed mechanics lien
           releases in compliance with both California Civil Code Section
           3262(d)(2) and either Section 3262(d)(3) or Section 3262(d)(4),
           (ii) Landlord has determined that no substandard work exists which
           adversely affects the mechanical, electrical, plumbing, heating,
           ventilating and air conditioning, lifesafety or other systems of
           the Building, the structure or exterior appearance of the Building,
           and (iii) Tenant's Architect delivers to Landlord a certificate, in
           a form reasonably acceptable to Landlord, certifying that the
           construction of the Tenant's Improvements in the Building has been
           substantially completed.


3.6.      Unused Allowance.  In the event that there remains any unused portion
          ----------------
     of the Tenant Improvement Allowance following disbursements by Landlord
     in connection with the Tenant's Improvements, any such amount shall be
     retained by Landlord. Tenant shall have no entitlement to any excess of
     the Tenant Improvement Allowance not in good faith consumed in the
     construction of the Tenant's Improvements.



                                   SECTION 4
                   CONSTRUCTION DRAWINGS; SUPERVISION OF WORK


4.1.      Selection of Architect/Construction Drawings.  Tenant hereby selects
          --------------------------------------------
     Interior Architects ("Tenant's Architect") to prepare the Construction
     Drawings, and Landlord hereby consents to such selection of Tenant's
     Architect.  Tenant 
<PAGE>
 
     shall enter into a written contract with Tenant's Architect reasonably
     acceptable to Landlord. To the extent required or appropriate, Tenant
     also shall select engineering consultants reasonably acceptable to
     Landlord ("Tenant's Engineers") to prepare and/or review plans and
     drawings relating to the Tenant's Improvements. The plans and
     specifications to be prepared by Tenant's Architect and Tenant's
     Engineers shall be known collectively as the "Construction Drawings". In
     connection with the preparation of the Construction Drawings, Tenant
     shall submit to Landlord, the schematic plans ("Schematic Plans") prior
     to and in connection with the Construction Drawings, which Schematic
     Plans shall be subject to the approval of Landlord which approval shall
     not be unreasonably withheld or delayed. Following the approval by
     Landlord of the final Schematic Plans, the Construction Drawings shall be
     prepared and a copy delivered to Landlord. The Construction Drawings
     shall be subject to Landlord's written approval, which shall not be
     unreasonably withheld or delayed. The Construction Drawings shall be full
     and complete and sufficient to obtain all necessary governmental permits
     and approvals required in connection with the construction of the
     Tenant's Improvements. Tenant's Architect shall respond within three (3)
     business days upon receipt of any written request of Landlord or
     Contractor for clarification or further definition in connection with the
     Construction Drawings. Tenant and Tenant's Architect shall verify in the
     field the actual dimensions and surface conditions of the Building, and
     Tenant and Tenant's Architect shall be solely responsible therefor and
     shall rely exclusively thereon. Landlord shall have no responsibility
     whatsoever for determination of the dimensions and conditions of the
     Building, and makes no representations in connection therewith.
     Landlord's review of the Construction Drawings as set forth in this
     Paragraph shall be for its sole purpose and shall not imply Landlord's
     review of the same, or obligate Landlord to review the same, for quality,
     design, code compliance or other like matters. Accordingly,
     notwithstanding that any Construction Drawings are reviewed by Landlord
     or its architect, engineers and consultants (if any), and notwithstanding
     any advice or assistance which may be rendered to Tenant by Landlord or
     Landlord's Architect, engineers, and consultants (if any), Landlord shall
     have no liability whatsoever in connection therewith and shall not be
     responsible for any omissions or errors contained in the Construction
     Drawings. No changes, modifications or alterations in the Construction
     Drawings may be made without the prior written consent of Landlord, which
     shall not be unreasonably withheld or delayed. Any delay in the
     completion of construction of the Tenant's Improvements resulting from
     any defect or omission in the Construction Drawings including, without
     limitation, the failure of the Construction Drawings to satisfy or to
     comply with any applicable law, code or regulations shall constitute a
     Tenant Delay for purposes of Paragraph 3.2 of the Lease.

4.2.      Permits.  Prior to the commencement of construction of the Tenant's
          -------
     Improvements, Landlord, with the assistance and cooperation of Tenant's
     Architect, shall submit the Construction Drawings as approved by Landlord
     to the appropriate municipal authorities and shall obtain all applicable
     building permits 
<PAGE>
 
     necessary to allow the Contractor to commence and fully complete the
     construction of the Tenant's Improvements (the "Permits"). Tenant shall
     reasonably cooperate with Landlord in taking such action as may be
     reasonably required so as to enable Landlord to obtain all such Permits
     and approvals.

4.3.      Landlord's Supervision Fee.  In connection with Landlord's review and
          --------------------------
     supervision of construction of the Tenant's Improvements as provided in
     this Work Letter, Landlord has designated Douglas C. Rosenberg ("Landlord's
     Supervisor") to serve as its representative and supervisor of the
     construction of the Tenant's Improvements and all related matters, and in
     connection with such function, Landlord shall be entitled to a supervision
     fee equal to two percent (2 %) of the total, final cost of constructing the
     Tenant's Improvements including all hard and soft costs and other matters
     constituting Tenant Improvement Allowance Items (exclusive only of the fee
     paid to Tenant's Architect and to Tenant's Engineers, if any) which fee
     shall be payable incrementally from time to time from the Tenant
     Improvement Allowance, Improvement Loan, Matching Funds and Tenant's Funds.
     The supervision fee shall be payable at least once each calendar month and
     shall generally be payable on a basis consistent with the percentage of the
     total cost for the Tenant's Improvements then having been incurred as
     approved by Landlord's Architect in accordance with Paragraph 3.5.1 above.



                                   SECTION 5
           TENANT'S COVENANTS AND BENCHMARKS; LEASE COMMENCEMENT DATE


5.1.      Tenant Indemnity.  Tenant hereby indemnifies Landlord from any loss,
          ----------------
     claims,  damages, actions or courses of action (including, without
     limitation, reasonable attorney's fees) arising from or relating to the
     actions of Tenant's agents, employees or contractors in the Premises or the
     Building or in the event Tenant shall conduct additional work to the
     Premises separate and apart from the Tenant Improvements prior to
     substantial completion of the Tenant Improvements, such as fixture
     installation or workstation set up, Tenant shall do so in strict compliance
     with any and all rules and regulations related thereto that Contractor or
     Landlord shall reasonably impose.  Tenant shall only have the right to
     conduct such activities prior to substantial completion provided that such
     activities do not interfere with Landlord's completion of the Tenant's
     Improvements.


5.2.      Tenant's Benchmarks.  The obligations of Tenant in connection with the
          -------------------
     Tenant's Improvements include the following (each a "Tenant Benchmark" and
     collectively, the "Tenant Benchmarks") which Tenant Benchmarks,
     notwithstanding any provision to the contrary of this Work Letter or the
     Lease, are to be completed by the date indicated below:
<PAGE>
 
                                                               Date of   
               Description of Tenant Benchmark                 Completion
               -------------------------------                 ----------

(i)   Tenant's written approval and delivery to Landlord       February 18, 1999
and the Contractor of final schematic drawings and written
identification of long lead architectural items, light
fixtures and other mechanical, electrical and plumbing 
items (and written agreement on specifications for each 
of such items).
(ii)  Delivery by Tenant to Landlord of final approval and     4 business days
release of the long lead architectural items described         following receipt
immediately above.  Landlord will provide to Tenant pricing    by Tenant of the
information and availability information in connection with    Long Lead 
the long lead items ("Long Lead Submission") for purposes of   Submission
obtaining Tenant's final approval with respect to all such
items.
(iii) Delivery by Tenant to Landlord and the Contractor of     March 26, 1999
complete construction drawings and specifications
(collectively, the "Construction Drawings").
(iv)  Final written approval by Tenant of the bid pricing of   4 business days
the Tenant's Improvements as set forth in the Construction     following receipt
Drawings which bid pricing shall be set forth in a             by Tenant of the
submission by Landlord and the Contractor to Tenant            Pricing 
("Pricing Submission").  It is anticipated that the Pricing    Submission
Submission will be delivered to Tenant on or about April 2nd, 
1999.
(v)   Written approval by Tenant of the total of the Tenant's  4 business days
Improvements as described in the Construction Drawings and     following 
the Pricing Submission as the Construction Drawings and        delivery by 
Pricing Submission may have been amended.  Landlord and        Landlord to 
Contractor shall deliver to Tenant after any amendments as     Tenant of final
required, a final form of Pricing Submission.                  Pricing 
                                                               Submission 




                                   SECTION 6
                                 MISCELLANEOUS


6.1.      Tenant's Representative.  Tenant has designated Laurie Guluarte as 
          -----------------------                                     
     its sole representative with respect to the matters set forth in this
     Work Letter, who shall have full authority and responsibility to act on
     behalf of the Tenant as required in this Work Letter.

6.2.     Landlord's Representative.  Landlord has designated Landlord's 
         -------------------------
     Supervisor, as defined above, as its sole representative with respect to
     the matters set forth in this Work Letter, who, until further notice to
     Tenant, shall have full authority and responsibility to act on behalf of
     the Landlord as required in this Work Letter.
<PAGE>
 
6.3.      Time of the Essence.  Unless otherwise indicated, all references 
          -------------------
     herein to a "number of days" shall mean and refer to calendar days. If
     any item requiring approval is timely disapproved by Landlord or Tenant,
     the procedure for preparation of the document and approval thereof shall
     be repeated until the document is approved by Landlord or Tenant, as the
     case may be. Unless otherwise provided in this Work Letter, Landlord's
     approval or Tenant's approval of any submittals required to be approved
     by the other shall be given or withheld within three (3) business days
     after receipt by the approving party of the submittal. In connection with
     any disapproved matter, any resubmittal by Landlord or Tenant, as the
     case may be, shall be approved or disapproved within two (2) business
     days and this procedure shall continue until Landlord's or Tenant's
     approval, as the case may be, of any submittal or resubmittal has been
     approved. For purposes of this Paragraph 6.3, references to submittals to
     and approvals by Tenant, shall be equally applicable to submittals to and
     approvals by Tenant's Architect.

6.4.      Hazardous Materials.  Landlord shall be responsible for the lawful
          -------------------
     treatment and/or disposal of all hazardous or toxic materials (as such
     terms may be defined from time to time by any governmental authority with
     jurisdiction) existing at the Building prior to the Lease Commencement Date
     which are disrupted or disturbed in connection with construction of the
     Improvement Work, with the exception of any such materials which were
     introduced to the Building or at the Site by Tenant or any of Tenant's
     representatives, agents, contractors or invitees.

6.5.      Landlord's Architect.  Landlord hereby designates Rebecca Nolan
          --------------------                                           
     ("Landlord's Architect") to act as architect on behalf of Landlord in
     connection with this Work Letter and the Lease.

6.6.      Incorporated into the Lease.  For all purposes, this Work Letter 
          ---------------------------
     shall be and is hereby deemed a part of the Lease, and to the extent
     necessary, they shall together be construed as one and the same document.


     IN WITNESS WHEREOF, the parties have executed and delivered this Work
Letter on the day and year first above written.


LANDLORD:                                     TENANT:
Rosenberg SOMA Investments II, LLC, a
Delaware limited liability company            USWeb Corporation, a Delaware 
                                              corporation
By:  TRC Investors II, LLC, a California
limited liability company, Manager            By: ___________________________
                                              Name: _________________________
     By:  The Rosenberg Company, a            Its: __________________________
          California corporation,       
          Manager 

          By:_____________________            By: ___________________________
             Douglas C. Rosenberg,            Name: _________________________
             President                        Its: __________________________

          By:_____________________
             Douglas C. Rosenberg,       
             Secretary