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                                                                   Exhibit 10.17


                              AMENDED AND RESTATED
                    REGISTRATION RIGHTS AND VOTING AGREEMENT


              THIS AMENDED AND RESTATED REGISTRATION RIGHTS AND VOTING
AGREEMENT (this "Agreement"), is made and entered into as of this 16th day of
December, 1998, by and between CORNERSTONE PROPERTIES INC., a Nevada corporation
(the "Company"), DUTCH INSTITUTIONAL HOLDING COMPANY, INC., a Delaware
corporation ("DIHC"), and STICHTING PENSIOENFONDS VOOR DE GEZONDHEID,
GEESTELIJKE EN MAATSCHAPPELIJKE BELANGEN, a stichting formed according to the
laws of The Netherlands ("PGGM").


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


              WHEREAS, pursuant to the terms of that certain Stock Purchase
Agreement (the "Purchase Agreement"), dated as of August 18, 1997, between the
Company and DIHC, and that certain Loan Purchase Agreement (the "Loan
Agreement") dated as of August 18, 1997, between the Company and PGGM, the
Company acquired certain shares of capital stock, partnership interests and
loans from DIHC and PGGM and issued shares of its Common Stock (as defined
below) to DIHC and PGGM; and

              WHEREAS, in connection with the Purchase Agreement, the Company,
DIHC and PGGM entered into a Registration Rights and Voting Agreement, dated as
of October 27, 1997 (the "Registration Rights Agreement"), which provided (I)
for the registration under the Securities Act of 1933, as amended, of certain
shares of Common Stock (II) for the nomination and election of certain persons
to serve on the Board of Directors of the Company, (III) for certain
restrictions regarding the transfer of shares of Common Stock and (IV) for
certain covenants regarding the operation of the Company's business; and

              WHEREAS, pursuant to the terms of that certain Stock Purchase
Agreement (the "Stock Purchase Agreement"), dated as of June 22, 1998, as
amended, between the Company and PGGM, the Company is issuing additional shares
of its Common Stock to PGGM; and

              WHEREAS, in connection with the Stock Purchase Agreement, the
parties desire to amend and restate the Registration Rights Agreement on the
terms set forth herein;

              NOW, THEREFORE, the parties agree as follows:

        1.    CERTAIN OTHER DEFINITIONS. Capitalized terms not otherwise defined
herein shall

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have the meanings ascribed to them in the Purchase Agreement. The capitalized
terms set forth below (in their singular and plural forms as applicable) shall
have the following meanings:

        1.1   "AFFILIATE" means, with respect to any specified Person, any other
Person that directly, or indirectly through one or more intermediaries,
controls, is controlled by, or is under common control with, such specified
Person.

        1.2   "BUSINESS COMBINATION" means any one of the following 
transactions:

              (i) Any merger or consolidation of the Company or any subsidiary
       thereof with any other Person (other than the Company);

              (ii) Any sale, lease, exchange, mortgage, pledge, transfer or
       other disposition by the Company (in one transaction or a series of
       transactions) to or with any Person of all or a substantial portion of
       the assets of the Company and its subsidiaries taken as a whole;

              (iii) The adoption of any plan or proposal for the liquidation or
       dissolution of the Company proposed by or on behalf of any Holder or its
       Affiliates that together own 25% or more of the issued and outstanding
       Common Stock; or

              (iv) Any reclassification of securities (including any reverse
       stock split), recapitalization of the Company, or any merger or
       consolidation of the Company with any subsidiary thereof or any other
       transaction to which the Company is a party which has the effect,
       directly or indirectly, of increasing the Holder Interest of such Holder
       or its Affiliates that together own 25% or more of the issued and
       outstanding Common Stock (whether or not with or into or otherwise
       involving such Holder or any of its Affiliates).

        1.3   "CLOSING DATE" has the meaning specified in Section 2.04 of the
Purchase Agreement.

        1.4   "COMMISSION" shall mean the United States Securities and Exchange
Commission and any successor federal agency having similar powers.

        1.5   "COMMON STOCK" shall mean the common stock without par value of 
the Company.

        1.6   "CONTROL" (including the terms "CONTROLLED BY" and "UNDER COMMON
CONTROL WITH"), with respect to the relationship between or among two or more
Persons, means the possession, directly or indirectly or as trustee, personal
representative or executor, of the power to direct or cause the direction of the
affairs or management of a Person, whether through the ownership of voting
securities, as trustee, personal representative or executor, by contract or
otherwise, including, without limitation, the ownership, directly or indirectly,
of securities having the power to elect a majority of the board of directors or
similar body governing the 

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affairs of such Person.

        1.7   "CURRENT MARKET PRICE" of each share of Common Stock shall mean
(I) the average of the closing prices of the Common Stock for the five New York
Stock Exchange trading days immediately preceding the day in question as
reported by THE WALL STREET JOURNAL under the New York Stock Exchange Composite
Transactions quotation system (or under any successor quotation system) or, if
the Common Stock is no longer traded on the New York Stock Exchange under the
quotation system under which such closing prices are reported or, if THE WALL
STREET JOURNAL no longer reports such closing prices, such closing prices as
reported by a newspaper or trade journal selected by the Company or (II) if no
such closing prices are available on such dates, the fair market value as
determined in good faith by the Board of Directors of the Company.

        1.8   "DEMAND OFFERING" shall mean a offering required to be effected
pursuant to Section 3.3 hereof.

        1.9   "DEMAND PROSPECTUS" shall mean the prospectus included in the
Shelf Registration Statement, including any preliminary prospectus, and any
amendment or supplement thereto, including any supplement relating to the terms
of the offering of any portion of the Demand Offering Securities covered by the
Demand Prospectus, and in each case including all material incorporated by
reference therein.

        1.10  "DEMAND OFFERING SECURITIES" shall mean the Shares held by DIHC
and PGGM or any subsequent Holder to whom this Agreement has, or rights to cause
the Company to register Shares in accordance with Section 3 have, been assigned
pursuant to Section 9, excluding (I) Shares that have been disposed of under the
Shelf Registration Statement or any other effective registration statement, (II)
Shares sold or otherwise transferred pursuant to Rule 144 under the Securities
Act, and (III) those Shares held by any single Holder if such Holder holds less
than 1% of the issued and outstanding shares of Common Stock and all of such
Shares are eligible for sale pursuant to Rule 144 under the Securities Act and
all of such Holder's Shares could be sold by such Holder in a single transaction
under Rule 144 under the Securities Act.

        1.11  "DEMAND OFFERING EXPENSES" shall mean any and all expenses
incurred by the Company in connection with Demand Offerings, including, without
limitation: (I) all Commission, stock exchange and National Association of
Securities Dealers, Inc. ("NASD") registration and filing fees, (II) all fees
and expenses incurred in connection with compliance with state securities or
"blue sky" laws (including reasonable fees and disbursements of counsel in
connection with qualification of any of the Demand Offering Securities under any
state securities or blue sky laws and the preparation of a blue sky memorandum)
and compliance with the rules of the NASD, (III) all expenses of any Persons in
preparing or assisting in preparing, word processing, printing and distributing
any Demand Prospectus, certificates and other documents relating to the
performance of and compliance with this Agreement, (IV) all fees and expenses
incurred in connection with the listing, if any, of any of the Demand Offering
Securities on any U.S. securities exchange or exchanges, and (V) the fees and
disbursements of counsel for 

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the Company and of the independent public accountants of the Company, including
the expenses of any special audits or "cold comfort" letters required by or
incident to such performance and compliance. Demand Offering Expenses shall
specifically exclude Selling Expenses and the fees and expenses of counsel
representing the Holders, all of which shall be borne by the Holders in all
cases.

        1.12  "DEMAND OFFERING REQUEST" shall have the meaning set forth in
Section 3.3(a) hereof.

        1.13  "DIHC" shall have the meaning set forth in the Preamble.

        1.14  "ENCUMBRANCE" means any security interest, pledge, mortgage, lien
(including, without limitation, environmental and tax liens), charge,
encumbrance, adverse claim, preferential arrangement, or restriction of any
kind, including, without limitation, any restriction on the use, voting,
transfer, receipt of income or other exercise of any attributes of ownership.

        1.15  "EQUITY SECURITY" means any (I) Common Stock, (II) securities of
the Company convertible into or exchangeable for Common Stock, and (III)
options, rights, warrants and similar securities issued by the Company to
acquire Common Stock.

        1.16  "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934, as
amended from time to time.

        1.17  "HOLDER" shall mean DIHC and PGGM (and their respective
transferees of Shares as permitted by this Agreement to whom this Agreement has,
or rights to cause the Company to register Shares in accordance with Section 3
have, been assigned pursuant to Section 9).

        1.18  "HOLDER INTEREST" means, with respect to any Holder, the
percentage of issued and outstanding Common Stock represented by the shares of
Common Stock owned by such Holder and its Affiliates; PROVIDED, HOWEVER, that
shares of Common Stock indirectly owned through an intermediary (I) of which
such Holder owns less than 1% of the issued and outstanding common shares or
(II) in connection with which Holder has no right to direct the vote of shares
of the Company shall not be included in the Holder Interest of such Holder.

        1.19  "INDEBTEDNESS" means, with respect to any Person, (a) all
indebtedness of such Person, whether or not contingent, for borrowed money, (b)
all obligations of such Person for the deferred purchase price of property or
services, (c) all obligations of such Person evidenced by notes, bonds,
debentures or other similar instruments, (d) all indebtedness created or arising
under any conditional sale or other title retention agreement with respect to
property acquired by such Person (even though the rights and remedies of the
seller or lender under such agreement in the event of default are limited to
repossession or sale of such property), (e) all obligations of such Person as
lessee under leases that have been or should be, in accordance with U.S. GAAP,
recorded as capital leases, (f) all obligations, contingent or otherwise, of
such 

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Person under acceptance, letter of credit or similar facilities, (g) all
obligations of such Person to purchase, redeem, retire, defease or otherwise
acquire for value any capital stock of such Person or any warrants, rights or
options to acquire such capital stock, valued, in the case of redeemable
preferred stock, at the greater of its voluntary or involuntary liquidation
preference plus accrued and unpaid dividends, (h) the greater of (I) the
principal amount and (II) the redemption value of any perpetual preferred stock
issued by such Person, (i) all Indebtedness of others referred to in clauses (a)
through (f) above guaranteed directly or indirectly in any manner by such
Person, or in effect guaranteed directly or indirectly by such Person through an
agreement (I) to pay or purchase such Indebtedness or to advance or supply funds
for the payment or purchase of such Indebtedness, (II) to purchase, sell or
lease (as lessee or lessor) property, or to purchase or sell services, primarily
for the purpose of enabling the debtor to make payment of such Indebtedness or
to assure the holder of such Indebtedness against loss, (III) to supply funds to
or in any other manner invest in the debtor (including any agreement to pay for
property or services irrespective of whether such property is received or such
services are rendered) or (IV) otherwise to assure a creditor against loss, and
(j) all Indebtedness referred to in clauses (a) through (f) above secured by (or
for which the holder of such Indebtedness has an existing right, contingent or
otherwise, to be secured by) any Encumbrance on property (including, without
limitation, accounts and contract rights) owned by such Person, even though such
Person has not assumed or become liable for the payment of such Indebtedness.

        1.20  "INCUMBENT DIRECTORS" shall mean (I) all of the individuals
constituting the board of directors of the Company on the date hereof, (II) all
individuals hereafter designated as nominees to the board of directors by the
New York State Teachers' Retirement System pursuant to a letter agreement dated
November 22, 1996, (III) all individuals hereafter designated as nominees to the
board of directors by Hexalon Real Estate, Inc. pursuant to a letter agreement
dated November 7, 1996, (IV) one individual at any time hereafter designated by
Deutsche Bank AG as a nominee to the board of directors, and (V) Messrs. William
Wilson III, Donald G. Fisher and Randall A. Hack as nominees to the board of
directors pursuant to an agreement dated as of June 22, 1998, as amended.

        1.21  "INITIAL PERCENTAGE" means the percentage of issued and
outstanding Common Stock represented immediately after the Closing by the shares
issued pursuant to the Purchase Agreement and the Loan Agreement.

        1.22  "LEVERAGE RATIO" shall mean the ratio of the Company's
Indebtedness to the Company's Total Market Capitalization.

        1.23  "MAXIMUM NUMBER" shall having the meaning set forth in Section
3.3(e) hereof.

        1.24  "PERMITTED TRANSFEREE" means any (I) mutual fund company, pension
fund, insurance company, investment company, any state, city, or county, or any
agency or instrumentality of a state, city, or county, or any state university
or state college, and any retirement system for the benefit of employees of any
of the foregoing, any religious or 

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educational organization or other passive institutional investor or (II) any
non-U.S. Person (as defined in Section 9.02 of the Charter Amendment) that is
not controlled by U.S. Persons (as defined in the Charter Amendment).

        1.25  "PERSON" means any individual, partnership, firm, corporation,
association, trust, unincorporated organization or other entity, as well as any
syndicate or group that would be deemed to be a person under Section 13(d)(3) of
the Exchange Act.

        1.26  "PGGM" shall have the meaning set forth in the Preamble.

        1.27  "PIGGYBACK REGISTRATION" shall have the meaning set forth in
Section 3.6(a) hereof.

        1.28  "PIGGYBACK REGISTRATION REQUEST" shall have the meaning set forth
in Section 3.6(a) hereof.

        1.29  "PUBLIC OFFERING" means a public offering of Common Stock pursuant
an effective registration statement under the Securities Act.

        1.30  The terms "REGISTER", "REGISTERED" and "REGISTRATION" refer to a
registration effected by preparing and filing a registration statement in
compliance with the Securities Act and the declaration or ordering of the
effectiveness of such registration statement by the Commission.

        1.31  "SECURITIES ACT" means the Securities Act of 1933, as amended.

        1.32  "SELLING EXPENSES" shall mean all underwriting discounts and
selling commissions and transfer taxes applicable to the sale of Shelf
Registrable Securities or Demand Offering Securities and disbursements of
underwriters.

        1.33  "SHARES" shall mean (a) the shares of Common Stock issued
pursuant to the Purchase Agreement, the Loan Agreement and the Stock Purchase
Agreement and (b) shares of Common Stock or any other securities which are
hereafter issued with respect to the shares referred to in Section 1.33(a) by
way of conversion, exchange, reclassification, dividend or distribution, whether
or not such securities have been offered and sold to the public.

        1.34  "SHELF PROSPECTUS" shall mean the prospectus included in the
Shelf Registration Statement, including any preliminary prospectus, and any
amendment or supplement thereto, including any supplement relating to the terms
of the offering of any portion of the Shelf Registrable Securities covered by
the Shelf Registration Statement, and in each case including all material
incorporated by reference therein.

        1.35  "SHELF REGISTRATION" shall mean the registration required to be
effected pursuant to Section 3.1 hereof.

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        1.36  "SHELF REGISTRABLE SECURITIES" shall mean the Shares held by DIHC
and PGGM or any subsequent Holder to whom this Agreement has, or rights to cause
the Company to register Shares in accordance with Section 3 have, been assigned
pursuant to Section 9, excluding (I) Shares that have been disposed of under the
Shelf Registration Statement or any other effective registration statement, (II)
Shares sold or otherwise transferred pursuant to Rule 144 under the Securities
Act, and (III) those Shares held by any single Holder if such Holder holds less
than 1% of the issued and outstanding shares of Common Stock and all of such
Shares are eligible for sale pursuant to Rule 144 under the Securities Act and
all of such Holder's Shares could be sold by such Holder in a single transaction
under Rule 144 under the Securities Act.

        1.37  "SHELF REGISTRATION EXPENSES" shall mean any and all expenses
incident to performance of or compliance with this Agreement, including, without
limitation: (I) all Commission, stock exchange and NASD registration and filing
fees, (II) all fees and expenses incurred in connection with compliance with
state securities or "blue sky" laws (including reasonable fees and disbursements
of counsel in connection with qualification of any of the Shelf Registrable
Securities under any state securities or blue sky laws and the preparation of a
blue sky memorandum) and compliance with the rules of the NASD, (III) all
expenses of any Persons in preparing or assisting in preparing, word processing,
printing and distributing the Shelf Registration Statement, any Shelf
Prospectus, certificates and other documents relating to the performance of and
compliance with this Agreement, (IV) all fees and expenses incurred in
connection with the listing, if any, of any of the Shelf Registrable Securities
on any securities exchange or exchanges, and (V) the fees and disbursements of
counsel for the Company and of the independent public accountants of the
Company, including the expenses of any special audits or "cold comfort" letters
required by or incident to such performance and compliance. Shelf Registration
Expenses shall specifically exclude Selling Expenses and the fees and
disbursements of counsel representing the Holders, all of which shall be borne
by the Holders in all cases.

        1.38  "SHELF REGISTRATION NOTICE" shall have the meaning set forth in
Section 3.2(b) hereof.

        1.39  "SHELF REGISTRATION STATEMENT" shall mean each registration
statement of the Company (and any other entity required to be a registrant with
respect to such registration statement pursuant to the requirements of the
Securities Act) that covers all of the Shelf Registrable Securities to be
offered on a delayed or continuous basis pursuant to Rule 415 under the
Securities Act, or any similar rule that may be adopted by the Commission, and
all amendments (including post-effective amendments) to such registration
statement, and all exhibits thereto and materials incorporated by reference
therein.

        1.40  "STANDSTILL PERIOD" means, with respect to any Holder, a period
of time commencing on the Closing Date and terminating on October 27, 2000 (the
date three years after the Closing Date).

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        1.41  "TOTAL MARKET CAPITALIZATION" shall mean the sum of (I) the
Company's total Indebtedness, plus (II) the product of (x) the number of issued
and outstanding shares of Common Stock, PLUS the number of shares of Common
Stock issuable upon conversion of issued and outstanding preferred stock (other
than convertible preferred stock subject to redemption at the option of the
holder) and issued and outstanding Units TIMES (y) the Current Market Price.

        1.42  "U.S. GAAP" means United States generally accepted accounting
principles and practices in effect from time to time applied consistently
throughout the periods involved.

        1.43  "UNITS" means units of limited partnership in Cornerstone
Properties Limited Partnership, a Delaware limited partnership.

     2. RESTRICTIONS ON TRANSFER.

        2.1   REPRESENTATIONS AND WARRANTIES OF PGGM. (a) PGGM and DIHC hereby
represent, acknowledge, covenant and agree as follows: (I) the Shares are being
acquired for PGGM's and DIHC's own account for investment and not with a view to
any distribution or public offering within the meaning of the Securities Act or
any state securities law; (II) the Shares have not been registered under the
Securities Act or any state securities law; (III) PGGM and DIHC is each an
"accredited investor" within the meaning of Rule 501 promulgated by the
Commission pursuant to the Securities Act; (IV) PGGM and DIHC have been
furnished with all information that PGGM or DIHC has requested for purposes of
evaluating the Company and each has had an opportunity to ask questions of and
receive answers from the Company regarding its business, assets, results of
operations, and financial condition; and (V) PGGM and DIHC will not sell or
otherwise transfer any of the Shares except upon the terms and conditions
specified herein.

        2.2   LEGENDS. Except as provided in Section 2.4, each certificate
representing the Shares issued to PGGM and DIHC or transferred to a subsequent
Holder pursuant to Section 2.3 shall include, in addition to the legends
relating to provisions of the Company's articles of incorporation, legends in
substantially the following form, PROVIDED that the first such legend shall not
be required if such transfer is being made in connection with a sale that is (I)
pursuant to a Public Offering or (II) exempt from registration pursuant to Rule
144 under the Securities Act or if the opinion of counsel referred to in Section
2.3 is to the further effect that such legend is not required in order to ensure
compliance with the Securities Act; PROVIDED FURTHER, that the second such
legend shall not be required if Sections 7.6 and 8 hereof do not apply to such
subsequent Holder:

                     THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
                     REGISTERED UNDER THE SECURITIES ACT OF 1933 OR ANY STATE
                     SECURITIES ACT AND MAY NOT BE SOLD OR TRANSFERRED IN THE
                     ABSENCE OF SUCH REGISTRATION OR AN

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                     EXEMPTION THEREFROM. 

                     SUCH SHARES MAY BE TRANSFERRED ONLY IN COMPLIANCE WITH THE
                     CONDITIONS SPECIFIED IN THE AMENDED AND RESTATED
                     REGISTRATION RIGHTS AND VOTING AGREEMENT DATED AS OF
                     DECEMBER 16, 1998, AMONG THE ISSUER AND THE OTHER
                     PARTY(IES) NAMED THEREIN, A COMPLETE AND CORRECT COPY OF
                     WHICH IS AVAILABLE FOR INSPECTION AT THE PRINCIPAL OFFICE
                     OF THE ISSUER AND WILL BE FURNISHED TO THE HOLDER HEREOF
                     UPON WRITTEN REQUEST AND WITHOUT CHARGE.

        2.3   NOTICE OF TRANSFER. Prior to any proposed assignment, transfer or
sale of any Shares, the Holder of such Shares shall give written notice to the
Company of Holder's intention to effect such assignment, transfer or sale, which
notice shall set forth the date of such proposed assignment, transfer or sale.
Holder shall also furnish to the Company a written agreement by the transferee
that it is taking and holding the same subject to the terms and conditions
specified in this Agreement and, except in transfers pursuant to a Public
Offering or under Rule 144 or Regulation S under the Securities Act, a written
opinion of Holder's counsel, in form reasonably satisfactory to the Company, to
the effect that the proposed transfer may be effected without registration under
the Securities Act.

        2.4   TERMINATION OF RESTRICTIONS. The restrictions set forth in this
Section 2 shall terminate and cease to be effective with respect to any of the
Shares (I) upon the sale of any such Shares which has been registered under the
Securities Act or is made pursuant to Rule 144 under the Securities Act or (II)
upon receipt by the Company of an opinion of counsel, which counsel and which
opinion are reasonably satisfactory to the Company, to the effect that
compliance with such restrictions is not necessary in order to comply with the
Securities Act with respect to the sale of the Shares. The restrictions with
respect to a Holder set forth in Sections 7.5 and 8 hereof shall terminate upon
the end of the Standstill Period. Whenever such restrictions shall so terminate,
the Holder of such Shares shall be entitled to receive from the Company, without
expense (other than transfer taxes, if any), certificates for such Shares not
bearing the respective legends set forth in Section 2.2.

     3. REGISTRATION UNDER SECURITIES ACT.

        3.1   SHELF REGISTRATION.

        (a) Within 20 days after the date hereof and upon the request of PGGM,
the Company will use its commercially reasonable efforts to cause to be filed a
Shelf Registration Statement, which, in accordance with Rule 429 under the
Securities Act, shall include a form of Shelf Prospectus for use with respect to
the Shelf Registrable Securities included in the 

<PAGE>

Registration Statement on Form S-3 (Registration No. 333-47149) filed by the
Company with the Commission on March 2, 1997, providing for the sale by the
Holders of all of the Shelf Registrable Securities in accordance with the terms
hereof and will use its commercially reasonable efforts to cause such Shelf
Registration Statement to be declared effective by the Commission as soon as
practicable thereafter. The Company agrees to use its commercially reasonable
efforts to keep the Shelf Registration Statement with respect to the Shelf
Registrable Securities continuously effective so long as Holder holds Shelf
Registrable Securities. Subject to Section 3.2(b) and Section 3.2(i), the
Company further agrees to amend the Shelf Registration Statement if and as
required by the rules, regulations or instructions applicable to the
registration form used by the Company for such Shelf Registration Statement or
by the Securities Act or any rules and regulations thereunder; PROVIDED,
HOWEVER, that the Company shall not be deemed to have used its commercially
reasonable efforts to keep the Shelf Registration Statement effective during the
applicable period if it voluntarily takes any action that would result in the
Holders not being able to sell Shelf Registrable Securities covered thereby
during that period, unless such action is required under applicable law or the
Company has filed a post-effective amendment to the Shelf Registration Statement
and the Commission has not declared it effective or except as otherwise
permitted by the last six sentences of Section 3.2(b). The Holders will provide
information reasonably requested by the Company in connection with the Shelf
Registration Statement as promptly as practicable after receipt of such request.
The "Plan of Distribution" section of the Shelf Registration Statement shall
permit negotiated purchases, secondary distributions, block trades, ordinary
brokerage transactions or a combination of such methods of sale, PROVIDED,
HOWEVER, that the Company's obligations under Sections 3.1 and 3.2 hereof shall
not include participation in underwritten offerings or other organized
distributions of securities, which obligations are limited to registrations
under Section 3.3 and 3.6 hereof.

        (b) EXPENSES. The Company shall pay all Shelf Registration Expenses in
connection with the registration pursuant to Section 3.1(a). The Holders shall
pay all Selling Expenses and the fees and disbursements of counsel representing
the Holders, relating to the sale or disposition of such Shelf Registrable
Securities pursuant to the Shelf Registration Statement.

        3.2   SHELF REGISTRATION PROCEDURES. In connection with the obligations
of the Company with respect to the Shelf Registration Statement contemplated by
Section 3.1 hereof, the Company shall:

        (a) prepare and file with the Commission, within the time period set
forth in Section 3.1(a) hereof, the Shelf Registration Statement, which Shelf
Registration Statement shall comply as to form in all material respects with the
requirements of the applicable form and include all financial statements
required by the Commission to be filed therewith;

        (b) subject to the last six sentences of this Section 3.2(b) and Section
3.2(i) hereof, (I) prepare and file with the Commission such amendments to such
Shelf Registration Statement as may be necessary to keep such Shelf Registration
Statement effective throughout the applicable period; (II) cause the Shelf
Prospectus to be amended or supplemented as required and to be filed as required
by Rule 424 or any similar rule that may be adopted under the 

<PAGE>

Securities Act; and (III) respond as promptly as practicable to any comments
received from the Commission with respect to the Shelf Registration Statement or
any amendment thereto. Notwithstanding anything to the contrary contained
herein, the Company shall not be required to take any of the actions described
in clauses (i), (ii) or (iii) in this Section 3.2(b), Section 3.2(d) or Section
3.2(i) with respect to the Shelf Registrable Securities (x) to the extent that
(I) in the reasonable opinion of the Company (A) securities laws applicable to
such sale would require the Company to disclose material non-public information
("Non-Public Information") and (B) the disclosure of such Non-Public Information
would materially adversely affect the Company; (II) such sale would occur during
the measurement period for determining the amount of Common Stock, or the amount
of any other consideration the amount of which will be based on the price of the
Common Stock, in connection with the acquisition of a business or assets by the
Company (a "Measurement Period"); OR (III) the Company is contemplating an
underwritten Public Offering of its securities and in the reasonable opinion of
the underwriters such sale would interfere materially with such Public Offering
by the Company (a "Financing Period"); and the Company delivers written notice
to the Holders to the effect that the Holders may not make offers or sales under
the Shelf Registration Statement for a period not to exceed 45 days from the
date of such notice; PROVIDED, HOWEVER, that the Company may deliver only four
such notices under this Section 3.2(b) and Section 3.4(a) within any
twelve-month period, PROVIDED, FURTHER, that the Company may deliver only two
such notices under this Section 3.2(b) and Section 3.4(a) within the
twelve-month period immediately following the expiration of the six-month period
referred to in Section 3.3(f)(i) hereof and (y) unless and until the Company has
received a written notice (a "Shelf Registration Notice") from any Holder that
such Holder intends to make offers or sales under the Shelf Registration
Statement as specified in such Shelf Registration Notice; PROVIDED, HOWEVER,
that the Company shall have ten business days to prepare and file any such
amendment or supplement after receipt of the Shelf Registration Notice. The
Measurement Period and Financing Period are collectively referred to herein as
the "Restricted Period." In the event the sale by the Holders of Shelf
Registrable Securities is deferred because of the existence of Non-Public
Information, the Company will notify the Holders promptly upon such Non-Public
Information being included by the Company in a filing with the Commission, being
otherwise disclosed to the public (other than through the actions of any
Holder), or ceasing to be material to the Company, and upon such notice being
given by the Company, the Holders shall again be entitled to sell Shelf
Registrable Securities as provided herein. In the event the sale by the Holders
of Shelf Registrable Securities is deferred because it is proposed to be made
during a Restricted Period, the Company shall specify, in notifying the Holders
of the deferral of its sale, when the Restricted Period will end, at which time
the Holders shall again be entitled to sell Shelf Registrable Securities as
provided herein. If the Restricted Period is thereafter changed, the Company
will promptly notify the Holders of such change and upon the end of the
Restricted Period as so changed, the Holders will again be entitled to sell
Shelf Registrable Securities as provided herein. If an agreement to which such
Restricted Period relates is terminated prior to the end of the Restricted
Period, the deferral period hereunder shall end immediately and the Company
shall promptly notify the Holders of the end of the deferral period;

        (c) promptly furnish the Holders after a Holder has delivered a Shelf

<PAGE>

Registration Notice to the Company, without charge, as many copies of each Shelf
Prospectus and any amendment or supplement thereto in order to facilitate the
public sale or other disposition of the Shelf Registrable Securities; the
Company consents to the use of the Shelf Prospectus and any amendment or
supplement thereto by the Holders of Shelf Registrable Securities in connection
with the offering and sale of the Shelf Registrable Securities covered by the
Shelf Prospectus or amendment or supplement thereto;

        (d) use its commercially reasonable efforts to register or qualify the
Shelf Registrable Securities by the time the Shelf Registration Statement is
declared effective by the Commission under all applicable state securities or
blue sky laws of such jurisdictions in the United States and its territories and
possessions as the Holders shall reasonably request in writing, keep each such
registration or qualification effective during the period such Shelf
Registration Statement is required to be kept effective or during the period
offers or sales are being made by the Holders after a Holder has delivered a
Shelf Registration Notice to the Company, whichever is shorter; PROVIDED,
HOWEVER, that in connection therewith, the Company shall not be required to (I)
qualify as a foreign corporation to do business or to register as a broker or
dealer in any such jurisdiction where it would not otherwise be required to
qualify or register but for this Section 3.2(d), (II) subject itself to taxation
in any such jurisdiction, or (III) file a general consent to service of process
in any such jurisdiction;

        (e) notify the Holders promptly and, if requested by a Holder, confirm
in writing, (I) when the Shelf Registration Statement and any post-effective
amendments thereto have become effective, (ii) when any amendment or supplement
to the Shelf Prospectus has been filed with the Commission, (III) of the
issuance by the Commission or any state securities authority of any stop order
suspending the effectiveness of the Shelf Registration Statement or any part
thereof or the initiation of any proceedings for that purpose, (IV) if the
Company receives any notification with respect to the suspension of the
qualification of the Shelf Registrable Securities for offer or sale in any
jurisdiction or the initiation of any proceeding for such purpose, and (V) of
the happening of any event during the period the Shelf Registration Statement is
effective as a result of which (A) such Shelf Registration Statement contains
any untrue statement of a material fact or omits to state any material fact
required to be stated therein or necessary to make the statements therein not
misleading or (B) the Shelf Prospectus as then amended or supplemented contains
any untrue statement of a material fact or omits to state any material fact
necessary in order to make the statements therein, in light of the circumstances
under which they were made, not misleading;

        (f) use its reasonable best efforts to obtain the withdrawal of any
order suspending the effectiveness of the Shelf Registration Statement or any
part thereof as promptly as possible;

        (g) promptly furnish to the Holders after a Holder has delivered a Shelf
Registration Notice to the Company, without charge, at least one conformed copy
of the Shelf Registration Statement and any post-effective amendment thereto
(without documents incorporated therein by reference or exhibits thereto, unless
requested);

<PAGE>

        (h) cooperate with the Holders to facilitate the timely preparation and
delivery of certificates representing Shelf Registrable Securities to be sold
and not bearing any Securities Act legend; and enable certificates for such
Shelf Registrable Securities to be issued for such numbers of shares as the
Holders may reasonably request at least two business days prior to any sale of
Shelf Registrable Securities;

        (i) subject to the last six sentences of Section 3.2(b) hereof, upon the
occurrence of any event contemplated by clause (v) of Section 3.2(e) hereof, use
its reasonable best efforts promptly to prepare and file an amendment or a
supplement to the Shelf Prospectus or any document incorporated therein by
reference or prepare, file and obtain effectiveness of a post-effective
amendment to the Shelf Registration Statement, or file any other required
document, in any such case to the extent necessary so that, as thereafter
delivered to the purchasers of the Shelf Registrable Securities, such Shelf
Prospectus as then amended or supplemented will not contain any untrue statement
of a material fact or omit to state any material fact necessary in order to make
the statements therein, in the light of the circumstances under which they are
made, not misleading;

        (j) make available for inspection by the Holders after a Holder has
provided a Shelf Registration Notice to the Company and any counsel, accountants
or other representatives retained by the Holders all financial and other
records, material corporate documents and properties of the Company and cause
the officers, directors and employees of the Company to supply all such material
records, documents or information reasonably requested by the Holders, counsel,
accountants or representatives in connection with the Shelf Registration
Statement; PROVIDED, HOWEVER, that such records, documents or information which
the Company determines in good faith to be confidential and notifies the
Holders, counsel, accountants or representatives in writing that such records,
documents or information are confidential shall not be disclosed by the Holders,
counsel, accountants or representatives unless (I) such disclosure is ordered
pursuant to a subpoena or other order from a court of competent jurisdiction, or
(II) such records, documents or information become generally available to the
public other than through a breach of this Agreement;

        (k) a reasonable time prior to the filing of the Shelf Registration
Statement or any amendment thereto, or any Shelf Prospectus or any amendment or
supplement thereto, provide copies of such document (not including any documents
incorporated by reference therein unless requested) to the Holders; and

        (l) use its reasonable best efforts to cause all Shelf Registrable
Securities to be listed on the New York Stock Exchange from and after the time
the Shelf Registration Statement is declared effective.

        The Company may require the Holders to furnish to the Company in writing
such information regarding the proposed distribution by the Holders as the
Company may from time to time reasonably request in writing.

<PAGE>

        In connection with and as a condition to the Company's obligations with
respect to the Shelf Registration Statement pursuant to Section 3.1 hereof and
this Section 3.2, the Holders covenant and agree that (I) they will not offer or
sell any Shelf Registrable Securities under the Shelf Registration Statement
until a Holder has provided a Shelf Registration Notice pursuant to Section
3.2(b) and have received copies of the Shelf Prospectus as then amended or
supplemented as contemplated by Section 3.2(c) and notice from the Company that
the Shelf Registration Statement and any post-effective amendments thereto have
become effective as contemplated by Section 3.2(e); (II) upon receipt of any
notice from the Company contemplated by Section 3.2(b) or Section 3.2(e) (in
respect of the occurrence of an event contemplated therein), the Holders shall
not offer or sell any Shelf Registrable Securities pursuant to the Shelf
Registration Statement until the Holders receive copies of the supplemented or
amended Shelf Prospectus contemplated by Section 3.2(i) hereof and receive
notice that any post-effective amendment has become effective, and, if so
directed by the Company, the Holders will deliver to the Company (at the expense
of the Company) all copies in its possession, other than permanent file copies
then in the Holders' possession, of the Shelf Prospectus as amended or
supplemented at the time of receipt of such notice; (III) upon the expiration of
60 days after the first date on which offers or sales can be made pursuant to
clause (i) above, the Holders will not offer or sell any Shelf Registrable
Securities under the Shelf Registration Statement until they have again complied
with the provisions of clause (i) above; (iv) each Holder and any of such
Holder's partners, officers, directors or Affiliates, if any, will comply with
the provisions of Regulation M under the Exchange Act as applicable to them in
connection with sales of Shelf Registrable Securities pursuant to the Shelf
Registration Statement; (V) each Holder and any of such Holder's partners,
officers, directors or Affiliates, if any, will comply with the prospectus
delivery requirements of the Securities Act as applicable to them in connection
with sales of Shelf Registrable Securities pursuant to the Shelf Registration
Statement; and (VI) each Holder and any of such Holder's partners, officers,
directors or Affiliates, if any, will enter into such written agreements as the
Company shall reasonably request to ensure compliance with clauses (iv) and (v)
above.

        3.3   DEMAND OFFERINGS.

        (a) REQUESTS FOR DEMAND OFFERING. PGGM, DIHC or a Holder or Holders
owning a majority of the Demand Offering Securities (the "Demand Initiating
Holder") may request the offering under the Securities Act of all or any portion
of the Demand Offering Securities held by such Holders for sale in the manner
specified in such request, including an underwritten offering. Upon receipt of
such request, the Company will promptly, but in any event within 20 days, give
written notice of such requested registration to all Holders of Demand Offering
Securities, and thereupon, in accordance with Section 3.4 hereof, the Company
will use its reasonable best efforts to effect the registration and sale of:

              (i) the Demand Offering Securities which the Company has been so
       requested to register by such Demand Initiating Holder;

              (ii) all other Demand Offering Securities which the Company has
       been 

<PAGE>

       requested to register by the other Holders thereof by written request
       delivered to the Company within 15 days after the giving of such written
       notice by the Company, and

              (iii) all shares of Common Stock which the Company may elect to
       register for its own account or for the account of others in connection
       with the offering of Demand Offering Securities pursuant to this Section
       3.3.

        Each initial request for a offering pursuant to this Section 3.3 shall
specify the number of Demand Offering Securities requested to be sold by the
Demand Initiating Holder, the method of disposition to be employed and the
Current Market Price of the Common Stock as of the date of such request. Any
request for an offering pursuant to this Section 3.3(a) shall be referred to
herein as a "Demand Offering Request" and all registrations requested pursuant
to this Section 3.3 are referred to herein as "Demand Offerings."

        (b) NUMBER OF DEMAND OFFERINGS. The Company shall not be required under
this Section 3.3 to effect more than eight Demand Offerings in the aggregate.
Notwithstanding anything to the contrary contained herein, if such method of
disposition is a firm commitment underwritten public offering, a registration
shall count as a Demand Offering only when all such Demand Offering Securities
shall have been sold pursuant thereto; PROVIDED, HOWEVER, that if a Demand
Prospectus filed by the Company pursuant to a Demand Offering Request shall be
abandoned or withdrawn at the behest of the Demand Initiating Holder, then,
unless the Holders shall, promptly upon receipt of a request by the Company
therefor supported by an invoice setting forth the expenses in reasonable
detail, reimburse the Company for the Demand Offering Expenses in respect of
such prospectus attributable to the Holders, the Company shall be deemed to have
effected a Demand Offering.

        (c) MINIMUM OFFERING AMOUNT. The Company shall not be required to comply
with this Section 3.3 unless the aggregate Current Market Price of all Demand
Offering Securities covered by the Demand Offering Request and the Demand
Offering Securities described in Section 3.3(a)(ii) shall be $75 million or more
(unless and to the extent the Demand Initiating Holder shall hold less than $75
million of Demand Offering Securities, in which case such minimum offering
amount shall be equal to the amount of Demand Offering Securities so held).

        (d) SELECTION OF UNDERWRITERS. If the method of disposition specified by
the Demand Initiating Holder shall be an underwritten public offering, the
Company may designate the managing underwriter of such offering, subject to the
approval of the Demand Initiating Holder which approval shall not be
unreasonably withheld.

        (e) PRIORITY ON DEMAND OFFERINGS. The Company shall be entitled to
include in any offering referred to in this Section 3.3, for sale in accordance
with the method of disposition specified by the Demand Initiating Holder shares
of Common Stock to be sold by the Company for its own account or by other
shareholders of the Company for their account. Nonetheless, whether or not the
Company desires to include any such additional shares in a 

<PAGE>

Demand Offering, if the managing underwriters advise the Company in writing that
in their opinion the number of securities requested to be included in such
offering exceeds the maximum number which can be included in such offering
without adversely affecting the marketability of the offering (the "Maximum
Number"), then the Company will limit the number of shares included in such
offering to the Maximum Number, and the shares offered shall be selected in the
following order of priority: (I) first, Demand Offering Securities covered by
the Demand Offering Request and the Demand Offering Securities described in
Section 3.3(a)(ii), subject to the proviso set forth in clause (iii) below, (II)
second, securities the Company proposes to sell and (III) third, securities
requested to be included in such registration pursuant to (A) the Stockholders'
Agreement, dated as of November 22, 1996, by and among the Company and the New
York State Teachers' Retirement System, (B) the Stockholders' Agreement, dated
as of November 7, 1996, by and between the Company and Hexalon Real Estate,
Inc., and (C) the Registration Rights and Lockup Agreement, dated as of December
16, 1998, by and among the Company and the parties named therein (the "Wilson
Registration Rights Agreement") pro rata among the holders thereof on the basis
of the number of shares requested to be included in such registration; PROVIDED
that the securities requested to be included pursuant to clauses (A) and (B)
shall not be reduced to less than one-third of the total number of shares in
such offering, and (IV) fourth, other securities requested to be included in
such registration.

        (f) EXCEPTION. Anything in this Section 3.3 to the contrary
notwithstanding, the Company shall not be required to file a Demand Prospectus
in connection with a Demand Offering (I) within twelve months after the closing
date of a Demand Offering or within six months after the effective date of any
registration statement (other than pursuant to Section 3.1 or a registration
statement on Form S-8 with respect to an employee benefit plan or a registration
statement on Form S-4 relating to securities to be issued in a merger or in
exchange for securities or assets of another Person) of the Company or (II) if
counsel for the Company, reasonably acceptable to the Demand Initiating Holder
shall deliver an opinion to the Holders to the effect that, pursuant to Rule 144
under the Securities Act or otherwise, the Holders can publicly offer and sell
the Demand Offering Securities as to which sale has been requested without
registration under the Securities Act.

        3.4   DEMAND OFFERING PROCEDURES. If and whenever the Company is
required by the provisions of Section 3.3 hereof to use its reasonable best
efforts to effect the sale of any of the Demand Offering Securities under the
Securities Act, the Company shall use its reasonable best efforts to effect the
registration and sale of the Demand Offering Securities in accordance with the
intended method of disposition thereof and will, as expeditiously as possible:

        (a) within 45 days after receiving a request for a Demand Offering,
prepare and file with the Commission a Demand Prospectus as a supplement to the
Shelf Registration Statement with respect to such Demand Offering Securities.
Notwithstanding anything to the contrary contained herein, the filing of such
Demand Prospectus may be delayed for a period not to exceed 45 days if (I) any
of the events specified in clause (x)(iii) of Section 3.2(b) hereof shall have
occurred, or (II) the Company is engaged in any program for the repurchase of
Common Stock or other securities of the Company and the Company provides written
notice to the 

<PAGE>

Demand Initiating Holder; PROVIDED, HOWEVER, that the Company may deliver only
four notices under this Section 3.4(a) and 3.2(b) hereof within any twelve-month
period; PROVIDED, FURTHER, that the Company may deliver only two such notices
under this Section 3.4(a) and Section 3.2(b) within the twelve-month period
immediately following the expiration of the six-month period referred to in
Section 3.3(f)(i) hereof.

        (b) prior to the filing described in paragraph (a) above, furnish to the
Holders copies of the Demand Prospectus and any amendments or supplements
thereto, which documents shall be subject to the approval of the Holders only
with respect to any statement in the Demand Prospectus which relates to the
Holders;

        (c) notify the Holders promptly and, if requested by the Holders,
confirm in writing, (I) when the Demand Prospectus has been filed with the
Commission, (II) when any amendment or supplement to the Demand Prospectus has
been filed with the Commission, (III) of the issuance by the Commission or any
state securities authority of any stop order suspending the effectiveness of the
Shelf Registration Statement or any part thereof or the initiation of any
proceedings for that purpose, (IV) if the Company receives any notification with
respect to the suspension of the qualification of the Demand Offering Securities
for offer or sale in any jurisdiction or the initiation of any proceeding for
such purpose, and (V) of the happening of any event during the period of the
offering pursuant to the Demand Prospectus as a result of which (A) such Shelf
Registration Statement contains any untrue statement of a material fact or omits
to state any material fact required to be stated therein or necessary to make
the statements therein not misleading or (B) the Demand Prospectus as then
amended or supplemented contains any untrue statement of a material fact or
omits to state any material fact necessary in order to make the statements
therein, in light of the circumstances under which they were made, not
misleading;

        (d) make every reasonable effort to obtain the withdrawal of any order
suspending the effectiveness of the Shelf Registration Statement or any part
thereof as promptly as possible;

        (e) furnish to the Holders after delivery of a Demand Offering Request
to the Company, without charge, at least one conformed copy of the Shelf
Registration Statement and any post-effective amendment thereto (without
documents incorporated therein by reference or exhibits thereto, unless
requested);

        (f) prepare and file with the Commission such amendments and supplements
to such Shelf Registration Statement and the Demand Prospectus used in
connection therewith as may be necessary and comply with the provisions of the
Securities Act with respect to the disposition of all Demand Offering Securities
covered by such Demand Prospectus in accordance with the Holders' intended
method of disposition set forth in such Demand Prospectus for such period;

        (g) furnish to the Holders and to each underwriter such number of copies
of the Shelf Registration Statement and the Demand Prospectus included therein
(including each 

<PAGE>

preliminary prospectus) and such other documents, as such persons may reasonably
request in order to facilitate the public sale or other disposition of the
Demand Offering Securities covered by such Demand Prospectus;

        (h) use its reasonable best efforts to register or qualify the Demand
Offering Securities covered by such Demand Prospectus under the securities or
blue sky laws of such jurisdictions as the Holders or, in the case of an
underwritten public offering, the managing underwriter, shall reasonably
request;

        (i) provide a transfer agent and registrar, which may be a single
entity, for all Demand Offering Securities;

        (j) use its reasonable best efforts to cause all Demand Offering
Securities to be listed on the New York Stock Exchange;

        (k) furnish on the date that Demand Offering Securities are delivered to
the underwriters for sale pursuant to such registration: (I) an opinion dated
such date of counsel representing the Company for the purposes of such
registration, addressed to the underwriters, stating that the Shelf Registration
Statement has become effective under the Securities Act and that (A) to the best
knowledge of such counsel, no stop order suspending the effectiveness thereof
has been issued and no proceedings for that purpose have been instituted or are
pending or contemplated under the Securities Act, (B) the Shelf Registration
Statement, the related Demand Prospectus, and each amendment or supplement
thereto, comply as to form in all material respects with the requirements of the
Securities Act and the applicable rules and regulations of the Commission
thereunder and that such counsel does not believe that any such Shelf
Registration Statement, Demand Prospectus, amendment or supplement contains a
misstatement of a material fact or an omission to state a material fact required
to be stated therein or necessary to make the statements made therein, in light
of the circumstances under which they were made, not misleading (except that
such counsel need express no opinion as to financial statements or financial or
statistical data contained therein) and (C) to such other effects as may
reasonably be requested by counsel for the underwriters or by the Holders or
their counsel, and (II) a "cold comfort" letter dated such date from the
independent public accountants retained by the Company, addressed to the
underwriters, stating that they are independent public accountants within the
meaning of the Securities Act and that, in the opinion of such accountants, the
financial statements of the Company included in the Shelf Registration Statement
or the Demand Prospectus, or any amendment or supplement thereto, comply as to
form in all material respects with the applicable accounting requirements of the
Securities Act, and such letter shall additionally cover such other financial
matters (including information as to the period ending no more than five
business days prior to the date of such letter) with respect to the registration
in respect of which such letter is being given as such underwriters may
reasonably request; and

        (l) make available for inspection by the Holders after the Demand
Initiating Holder has provided a Demand Offering Request to the Company and any
counsel, accountants or other representatives retained by the Holders all
financial and other material records, pertinent 

<PAGE>

corporate documents and properties of the Company and cause the officers,
directors and employees of the Company to supply all such material records,
documents or information reasonably requested by the Holders, counsel,
accountants or representatives in connection with the Demand Prospectus;
PROVIDED, HOWEVER, that such records, documents or information which the Company
determines in good faith to be confidential and notifies the Holders, counsel,
accountants or representatives in writing that such records, documents or
information are confidential shall not be disclosed by Holders, counsel,
accountants or representatives unless (I) such disclosure is ordered pursuant to
a subpoena or other order from a court of competent jurisdiction, or (II) such
records, documents or information become generally available to the public other
than through a breach of this Agreement.

For purposes of paragraphs (a) and (f) of this Section 3.4, the period of
distribution of Demand Offering Securities in a firm commitment underwritten
public offering shall be deemed to be that period during which the underwriters
in such offering require in an underwriting agreement in the form customarily
used by such underwriters for comparable transactions that the Company keep a
registration statement effective to permit each underwriter to complete the
distribution of all securities purchased by it, and the period of distribution
of Demand Offering Securities in any other registration shall be deemed to
extend until the earlier of the sale of all Demand Offering Securities covered
thereby or nine months after the effective date thereof.

        In connection with each registration hereunder, each Holder will furnish
to the Company in writing such information with respect to itself and the
proposed distribution by itself as shall be reasonably necessary in order to
assure compliance with federal and applicable state securities laws. Reasonable
compliance with the obligation to furnish such information shall be a condition
to the rights afforded such Holder hereunder. In addition, each Holder and any
of its partners, officers, directors or Affiliates, if any, (I) will comply with
the provisions of Regulation M as applicable to them in connection with sales of
Demand Offering Securities pursuant to the Demand Prospectus; (II) will comply
with the prospectus delivery requirements of the Securities Act as applicable to
them in connection with sales of Demand Offering Securities pursuant to the
Demand Prospectus; and (III) will enter into such written agreements as the
Company shall reasonably request to ensure compliance therewith.

        In connection with each registration pursuant to Section 3.3 hereof
covering an underwritten public offering, the Company agrees to enter into a
written agreement with the managing underwriter selected in the manner herein
provided in such form and containing such provisions as are customary in the
securities business for such an arrangement between major underwriters and
companies of the Company's size and investment stature; PROVIDED that such
agreement shall not contain any such provision applicable to the Company which
is inconsistent with the provisions hereof; PROVIDED, FURTHER that the time and
place of the closing under said agreement shall be as mutually agreed upon
between the Company and such managing underwriter.

        3.5   DEMAND OFFERING EXPENSES. In connection with any Demand Offering,
the Company shall pay all Demand Offering Expenses and the Holders shall pay all
Selling 

<PAGE>

Expenses applicable to the shares sold by the Holders.

        3.6   PIGGYBACK REGISTRATIONS.

        (a) RIGHT TO PIGGYBACK. In the event that a Holder is not permitted to
effect sales under the Shelf Registration Statement under Section 3.2(b)(x)(iii)
hereof or the Holders are not permitted to effect Demand Offering due to Section
3.4(a)(i), Holders shall become entitled to the rights of this Section 3.6. The
Company will promptly (but in any event within 30 days) give written notice to
the Holders of its intention to effect such registration and a description of
any underwriting agreement to be entered into with respect thereto and will
include in such registration all Shelf Registrable Securities or Demand Offering
Securities with respect to which the Company has received written requests for
inclusion within 15 days after the receipt of the Company's notice (a "Piggyback
Registration Request"); PROVIDED, HOWEVER, that the Company shall not be
required to include Shelf Registrable Securities or Demand Offering Securities
in the securities to be registered pursuant to a registration statement on any
form which limits the amount of securities which may be registered by the issuer
and/or selling security holders if, and to the extent that, such inclusion would
make the use of such form unavailable. In the event that any Piggyback
Registration shall be, in whole or in part, an underwritten public offering of
Common Stock, the Holders shall agree that such Demand Offering Securities or
Shelf Registrable Securities are to be included in the underwriting on the same
terms and conditions as the shares of Common Stock otherwise being sold through
underwriters under such registration.

        (b) PRIORITY ON PRIMARY REGISTRATIONS. If a Piggyback Registration is an
underwritten primary registration on behalf of the Company, and the managing
underwriters advise the Company in writing that in their opinion the number of
shares requested to be included in such registration exceeds the Maximum Number,
the Company will limit the number of shares included in such registration to the
Maximum Number, and the shares registered shall be selected in the following
order of priority: (I) first, securities the Company proposes to sell, subject
to the proviso set forth in clause (ii) below, (II) second, (A) Shelf
Registrable Securities or Demand Offering Securities covered by Piggyback
Registration Requests, (B) securities requested to be included in such
registration pursuant to the Wilson Registration Rights Agreement, and (C)
securities requested to be included in such registration pursuant to (x) the
Stockholders' Agreement, dated as of November 22, 1996, by and among the Company
and the New York State Teachers' Retirement System and (y) the Stockholders'
Agreement, dated as of November 7, 1996, by and between the Company and Hexalon
Real Estate, Inc., pro rata among the holders thereof on the basis of the number
of shares requested to be included in such registration; PROVIDED that the
securities requested to be included pursuant to clauses (x) and (y) shall not be
reduced to less than one-third of the total number of shares in such offering
and (III) third, other securities requested to be included in such registration.

        (c) PRIORITY ON SECONDARY REGISTRATIONS. If a Piggyback Registration is
an underwritten secondary registration on behalf of holders of the Company's
securities, and the managing underwriters advise the Company in writing that in
their opinion the number of securities requested to be included in such
registration exceeds the Maximum Number, the 

<PAGE>

Company will include in such registration the shares requested to be included
therein by the holders requesting such registration and the Shelf Registrable
Securities and Demand Offering Securities covered by Piggyback Registration
Requests and any other securities requested to be included in such registration,
pro rata among the holders thereof on the basis of the number of shares
requested to be included in such registration; PROVIDED, HOWEVER, that if the
holders requesting registration are doing so pursuant to demand registration
rights of such holders, such holders' shares shall take priority over any Shelf
Registrable Securities and Demand Offering Securities and any other securities
requested to be included, which shall be included on a pro rata basis, subject
to the proviso set forth in Section 3.6(b)(ii)(C).

        3.7   INDEMNIFICATION.

        (a) INDEMNIFICATION BY THE COMPANY. To the extent permitted by law, the
Company shall indemnify and hold harmless the seller of any Shares covered by
any registration statement filed pursuant to Section 3, its directors, trustees
and officers, each other person who participates as an underwriter in the
offering or sale of such securities and each other person, if any, who controls
such seller or any such underwriter within the meaning of the Securities Act
against any losses, claims, damages, liabilities or expenses, joint or several,
to which such seller or any such director, trustee or officer or participating
or controlling person may become subject under the Securities Act or otherwise,
insofar as such losses, claims, damages, liabilities or expenses (or related
actions or proceedings) arise out of or are based upon (X) any untrue statement
or alleged untrue statement of any material fact contained in any registration
statement under which such securities were registered under the Securities Act,
any preliminary prospectus, final prospectus or summary prospectus contained in
such registration statement, or any amendment or supplement to such registration
statement, or any document incorporated by reference in such registration
statement, or (Y) any omission or alleged omission to state therein a material
fact required to be stated therein or necessary to make the statements therein
not misleading, and the Company will reimburse such seller, and each such
director, trustee, officer, participating person and controlling person for any
legal or any other expenses reasonably incurred by them in connection with
investigating or defending any such loss, claim, liability, action or
proceeding, PROVIDED that the Company shall not be liable in any such case (1)
to the extent that any such loss, claim, damage, liability or expense (or action
or proceeding in respect thereof) arises out of or is based upon an untrue
statement or alleged untrue statement or omission or alleged omission made in
such registration statement, any such preliminary prospectus, final prospectus,
summary prospectus, amendment or supplement in reliance upon and in conformity
with written information furnished to the Company through an instrument duly
executed by such seller or any such director, trustee, officer, participating
person or controlling person specifically stating that it is for use in the
preparation of such registration statement or (2) to the extent any amount paid
in settlement of any such loss, claim, damage, liability or action of such
settlement is effected without the written consent of the Company (which consent
shall not be unreasonably withheld). Such indemnity shall remain in full force
and effect regardless of any investigation made by or on behalf of such seller
or any such director, trustee, officer, participating person or controlling
person and shall survive the transfer of such securities by such seller. The
Company shall agree to make provision for contribution 

<PAGE>

relating to such indemnity as shall be reasonably requested by any seller of
Shares or the underwriters.

        (b) INDEMNIFICATION BY THE SELLERS. The Company may require, as a
condition to including any Shares in any registration statement filed pursuant
to Section 3, that the Company shall have received an undertaking satisfactory
to it from each prospective seller of such securities, severally and not
jointly, to indemnify and hold harmless (in the same manner and to the same
extent as set forth in Section 3.6(a)) the Company, each director of the
Company, each officer of the Company who shall sign such registration statement
and each other person, if any, who controls the Company within the meaning of
the Securities Act, with respect to any untrue statement in or omission from
such registration statement, any preliminary prospectus, final prospectus or
summary prospectus included in such registration statement, or any amendment or
supplement to such registration statement, of a material fact if such statement
or omission was made in reliance upon and in conformity with written information
furnished to the Company through an instrument duly executed by such seller
specifically stating that it is for use in the preparation of such registration
statement, preliminary prospectus, final prospectus, summary prospectus,
amendment or supplement. Such indemnity shall remain in full force and effect
regardless of any investigation made by or on behalf of the Company or any such
director, officer or controlling person and shall survive the transfer of such
securities by such seller.

        (c) INDEMNIFICATION PROCEDURE. Promptly after receipt by any party
entitled to indemnification pursuant to Section 3.7(a) or 3.7(b) of this
Agreement (an "Indemnified Party") of notice by a third party of any complaint
or the commencement of any action or proceeding with respect to which
indemnification is being sought hereunder, such Indemnified Party shall notify
the party obligated to provide such indemnification (the "Indemnifying Party")
of such complaint or of the commencement of such action or proceeding; PROVIDED,
HOWEVER, that the failure to so notify the Indemnifying Party shall not relieve
the Indemnifying Party from liability for such claim arising otherwise than
under this Agreement, and such failure to so notify the Indemnifying Party shall
relieve the Indemnifying Party from liability which the Indemnifying Party may
have hereunder with respect to such claim if, but only if, and only to the
extent that, such failure to notify the Indemnifying Party results in the
forfeiture by the Indemnifying Party of material rights and defenses otherwise
available to the Indemnifying Party with respect to such claim. The Indemnifying
Party shall have the right, upon written notice to the Indemnified Party, to
assume the defense of such action or proceeding, including the employment of
counsel reasonably satisfactory to the Indemnified Party and the payment of the
fees and disbursements of such counsel. In the event, however, that the
Indemnifying Party declines or fails to assume the defense of the action or
proceeding or to employ counsel reasonably satisfactory to the Indemnified
Party, in either case in a timely manner, then such Indemnified Party may employ
counsel to represent or defend it in any such action or proceeding and the
Indemnifying Party shall pay the reasonable fees and disbursements of such
counsel as incurred; PROVIDED, HOWEVER, that the Indemnifying Party shall not be
required to pay the fees and disbursements of more than one counsel for all
Indemnified Parties in any jurisdiction in any single action or proceeding. In
any action or proceeding with respect to which indemnification is being sought
hereunder, the Indemnified Party or the Indemnifying Party, whichever is not
assuming the defense of such 

<PAGE>

action, shall have the right to participate in such litigation and to retain its
own counsel at such party's own expense. The Indemnifying Party or the
Indemnified Party, as the case may be, shall at all times use reasonable best
efforts to keep the Indemnifying Party or the Indemnified Party, as the case may
be, reasonably apprised of the status of the defense of any action, the defense
of which it is maintaining and to cooperate in good faith with the Indemnifying
Party or the Indemnified Party, as the case may be, with respect to the defense
of any such action.

        No Indemnified Party may settle or compromise any claim or consent to
the entry of any judgment with respect to which indemnification is being sought
hereunder without the prior written consent of the Indemnifying Party, unless
such settlement, compromise or consent includes an unconditional release of the
Indemnifying Party from all liability arising out of such claim. An Indemnifying
Party may not, without the prior written consent of the Indemnified Party,
settle or compromise any claim or consent to the entry of any judgment with
respect to which indemnification is being sought hereunder unless such
settlement, compromise or consent includes an unconditional release of the
Indemnified Party from all liability arising out of such claim and does not
contain any equitable order, judgment or term which in any manner affects,
restrains or interferes with the business of the Indemnified Party or any of the
Indemnified Party's affiliates.

        In the event an Indemnified Party shall claim a right to payment
pursuant to this Agreement, such Indemnified Party shall send written notice of
such claim to the appropriate Indemnifying Party. Such notice shall specify the
basis for such claim. As promptly as possible after the Indemnified Party has
given such notice, such Indemnified Party and the appropriate Indemnifying Party
shall establish the merits and amount of such claim (by mutual agreement or
otherwise) and, within five business days of the final determination of the
merits and amount of such claim, the Indemnifying Party shall deliver to the
Indemnified Party immediately available funds in an amount equal to such claim
as determined hereunder.

        If for any reason the indemnification provided for in this Section 3.7
is unavailable to an Indemnified Party or is insufficient to hold it harmless as
contemplated by this Section 3.7, then the Indemnifying Party shall contribute
to the amount paid or payable by the Indemnified Party as a result of such loss,
claim, damage or liability in such proportion as is appropriate to reflect the
relative fault of the Indemnified Party and the Indemnifying Party, as well as
any other relevant equitable considerations; PROVIDED that in no event shall the
liability of any Holder for such contribution and indemnification exceed, in the
aggregate, the dollar amount of the proceeds received by such Holder upon the
sale of Shares giving rise to such indemnification and contribution obligations.

        The obligations of the parties under this Section 3.7 shall be in
addition to any liability which any party may otherwise have to any other party.

        3.8   LIMITATIONS ON REGISTRATION RIGHTS OF OTHERS. The Company
represents and warrants that, except pursuant to this Agreement and pursuant to
rights granted pursuant to the agreements set forth on Exhibit A hereto, it has
not granted to any Person the right to request 

<PAGE>

or require the Company to register any securities issued by the Company.

     4. RULE 144. The Company shall comply with the requirements of Rule
144 under the Securities Act, as such Rule may be amended from time to time (or
any similar rule or regulation hereafter adopted by the Commission), regarding
the availability of current public information to the extent required to enable
any Holder of Shares to sell Shares without registration under the Securities
Act pursuant to Rule 144 (or any similar rule or regulation). Upon the request
of any Holder of Shares, the Company will deliver to such Holder a written
statement as to whether it has complied with such requirements.

     5. AMENDMENTS AND WAIVERS. This Agreement may be amended and the
Company may take any action herein prohibited, or omit to perform any act herein
required to be performed by it, only if the Company shall have obtained the
written consent to such amendment, action or omission to act, of the Holder or
Holders of a majority of the Shares (and, in the case of any amendment, action
or omission to act which adversely affects any specific Holder of Shares or a
specific group of Holders of Shares, the written consent of each such Holder or
Holders of a majority of the Shares held by such group). Each Holder of any
Shares at the time shall be bound by any consent authorized by this Section 5.

     6. NOMINEES FOR BENEFICIAL OWNERS. In the event that any Shares are held 
by a nominee for the beneficial owner thereof, the beneficial owner thereof 
may, at its election, be treated as the Holder of such Shares for purposes of 
any request or other action by any Holder or Holders of Shares pursuant to 
this Agreement or any determination of any number or percentage of shares of 
Shares held by any Holder or Holders of Shares contemplated by this 
Agreement. If the beneficial owner of any Shares so elects, the Company may 
require assurances reasonably satisfactory to it of such owner's beneficial 
ownership of such Shares.

     7. COVENANTS OF THE PARTIES.

        7.1   BOARD OF DIRECTORS.

        (a) So long as PGGM and DIHC and their respective Affiliates own in the
aggregate 5% or more of the issued and outstanding shares of Common Stock, the
Company shall take all action necessary to nominate for election to the board of
directors of the Company (the "Board") at any annual or special meeting of
stockholders at which directors are being elected (or in connection with a
written consent in lieu of a meeting pursuant to which directors are proposed to
be elected) two individuals designated by PGGM ("PGGM Directors").

        (b) From the date hereof until the earlier to occur of (I) the date as
of which PGGM and DIHC and their respective Affiliates own in the aggregate less
than 25% of the issued and outstanding shares of Common Stock or (II) October
31, 2002:

              (i) the Company shall take all action necessary to ensure that one
       PGGM Director is appointed to the board affairs committee of the Board
       (the "Committee").

<PAGE>

              (ii) All nominees for election as directors of the Company by the
       Board (other than Incumbent Directors and PGGM Directors nominated
       pursuant to Section 7.1(a) who are employees, officers or directors of
       PGGM or DIHC) shall be persons not affiliated with PGGM or DIHC or any of
       their respective Affiliates and shall be made with the unanimous approval
       of the Committee;

              (iii) PGGM and DIHC shall vote (or provide written consent with
       respect to) all shares of Common Stock over which it exercises voting
       authority in favor of the persons nominated as PGGM Directors pursuant to
       Section 7.1(a) and all nominees nominated in accordance with Section
       7.1(b)(ii) and all Incumbent Directors nominated for election as
       directors of the Company by the Board;

              (iv) In the event of any vacancy on the Board, whether caused by a
       director's resignation, removal, death or otherwise, the Company shall
       take all action necessary to ensure that the successor to the director
       whose absence from the Board caused such vacancy shall be a PGGM Director
       if the director who caused such vacancy was a PGGM Director; and

              (v) The Company shall not increase the number of directors
       constituting the full Board without the unanimous approval of the
       Committee.

        (c) So long as PGGM and DIHC and their respective Affiliates own in the
aggregate 2.5% or more of the issued and outstanding shares of Common Stock, the
Company shall not without the prior written consent of PGGM modify the policy of
the Company with respect to its interest in One Norwest Center, Denver,
Colorado, adopted at a meeting of the Board on August 13, 1997.

        (d) From the date of adoption of the Amended and Restated Bylaws of the
Company in the form attached hereto as Annex A (the "Amended Bylaws") until the
third anniversary of such date:

              (i) PGGM and DIHC shall vote (or provide written consent with
       respect to) all shares of Common Stock over which it exercises voting
       authority in favor of the persons nominated as Wilson Directors (as
       defined in the Amended Bylaws) pursuant to Section 3.03(a) of the Amended
       Bylaws and approved by the Committee as set forth in Section 3.02 of the
       Amended Bylaws; and

              (ii) PGGM and DIHC shall use commercially reasonable efforts to
       cause the PGGM Directors, in considering the nominees proposed by Wilson
       III (or the Wilson III Designee) (as defined in the Amended Bylaws) for
       inclusion in the Board's list of nominees for election as director to
       approve in all cases Wilson III, and in considering other persons
       nominated as Wilson Directors, not to unreasonably withhold their
       approval.

<PAGE>

        7.2   LEVERAGE RATIO. So long as PGGM and DIHC and their respective
Affiliates own in the aggregate 2.5% or more of the issued and outstanding
shares of Common Stock, the Company shall at all times maintain a Leverage Ratio
not in excess of 0.45 to 1; PROVIDED, HOWEVER, THAT NOTWITHSTANDING THE
FOREGOING, (I) THE COMPANY MAY AT ANY TIME INCUR INDEBTEDNESS IN AN AMOUNT WHICH
DOES NOT EXCEED THE PRINCIPAL AMOUNT OF OUTSTANDING INDEBTEDNESS OF THE COMPANY
EXTENDED, REFINANCED, RENEWED OR REPLACED WITH THE PROCEEDS THEREOF, PLUS ANY
COSTS ASSOCIATED WITH THE EXTENSION REFINANCING, RENEWAL OR REPLACEMENT, EVEN IF
SUCH INCURRENCE CAUSES THE LEVERAGE RATIO TO EXCEED 0.45 TO 1, (II) THE COMPANY
MAY INCUR INDEBTEDNESS IF, AS OF THE DATE ON WHICH THE COMPANY ENTERS INTO A
BINDING COMMITMENT WITH RESPECT TO SUCH INDEBTEDNESS, THE LEVERAGE RATIO
INCLUDING SUCH INDEBTEDNESS DID NOT EXCEED 0.45 TO 1 AND (III) WITH RESPECT TO
LINES OF CREDIT, THE COMPANY MAY INCUR INDEBTEDNESS UNDER SUCH LINE, IF, AS OF
THE DATE THE COMPANY ENTERS INTO THE LINE OF CREDIT, THE LEVERAGE RATIO
INCLUDING THE ENTIRE AMOUNT OF INDEBTEDNESS AVAILABLE UNDER SUCH LINE DID NOT
EXCEED 0.45 TO 1.

        7.3   DOMESTIC REIT STATUS. So long as PGGM and DIHC and their
respective Affiliates own in the aggregate 2.5% or more of the issued and
outstanding shares of Common Stock, the Company shall not issue any Equity
Securities in connection with any Public Offering or other sale to any Non-U.S.
Person (as defined in Section 9.02 of the Charter Amendment), other than in
connection with stock splits or stock dividends or under the Company's dividend
reinvestment plan or stock option or management incentive compensation plans;
PROVIDED, HOWEVER, that the Company, in connection with any Public Offering of
Equity Securities, may issue and sell up to 15% of the securities issued in such
offering to Non-U.S. Persons.

        7.4   HOLDBACK AGREEMENTS. Each Holder agrees, if so requested prior to
December 31, 1998, by the managing underwriter in any Public Offering by the
Company, not to effect any sale or distribution of Common Stock (other than as
part of such Public Offering) within such periods prior to and after the
effective date of such registration statement as the managing underwriter may
request and as may be required of executive officers and directors of the
Company after the effective date of such registration statement; PROVIDED that
no Holder shall be required to enter into more than one such agreement. After
December 31, 1998, each Holder will consider entering into such agreements if so
requested.

        7.5   RESTRICTIONS ON TRANSFER. During the Standstill Period, any Holder
and its Affiliates owning 25% or more of the issued and outstanding shares of
Common Stock, shall not assign, transfer or sell any Shares to any Person or
such Person's Affiliates (other than a Permitted Transferee that agrees in
writing to be bound by the provisions of this Agreement) in any single
transaction or series of related transactions if, after such transaction or
transactions, such Person and such Person's Affiliates would own more than 10%
of the then issued and outstanding shares of Common Stock other than transfers
of shares from DIHC to PGGM.

        7.6   OWNERSHIP LIMIT. The Company has taken and will continue to take
all action necessary to ensure that issuance of the Shares to DIHC, DIHC Market
Square, Inc. and PGGM pursuant to the Purchase Agreement and the Loan Agreement
shall not be deemed a 

<PAGE>

violation of Article 8 of the Company's articles of incorporation. Whenever PGGM
or DIHC (or DIHC Market Square, Inc.) proposes to transfer any Shares to any
Person, in accordance with the provisions of Section 8.03 of the articles of
incorporation of the Company, the Board shall determine whether the proposed
transfer would jeopardize the Company's status as a real estate investment trust
(a "REIT") under Section 856 of the Internal Revenue Code of 1986, as amended.
If the Board determines that it would not so jeopardize the Company's REIT
status, or if it receives an opinion of counsel, which counsel and opinion are
reasonably satisfactory to the Board, to the effect that such proposed transfer
will not jeopardize the Company's status as a REIT, the Board shall determine
that such transferee will not be treated as a "Person" within the meaning of
Section 8.03(b) of the Company's articles of incorporation and therefore the
ownership of Shares by such transferee will be exempt from the restrictions
imposed by Article 8 of the Company's articles of incorporation. If the Board
determines that the proposed transfer would jeopardize the Company's REIT
status, the Company shall provide a written explanation to DIHC and PGGM of the
basis for its determination and shall provide reasonable access to information
regarding the Company's shareholders to DIHC and PGGM.

        7.7   TRANSFERS TO PGGM. The Company shall take all action necessary to
ensure that any transfer of Shares from DIHC or DIHC Market Square, Inc. to PGGM
shall not be deemed a violation of Article 8 or Section 9.01 of the Company's
articles of incorporation.

        7.8   SHARE REPURCHASES. So long as DIHC and PGGM and their respective
Affiliates own in the aggregate 25% or more of the issued and outstanding shares
of Common Stock, in the event the Company proposes to repurchase any shares of
Common Stock from any holder thereof owning together with its Affiliates 5% or
more of the issued and outstanding shares of Common Stock, DIHC and PGGM shall
have the right to require the Company to repurchase a number of shares of Common
Stock held by DIHC and PGGM equal to the product of (I) the total number of
shares proposed to be repurchased and (II) a fraction, the numerator of which is
(A) the number of Shares owned by DIHC and PGGM and their respective Affiliates
and the denominator of which is (B) the sum of the number of shares of Common
Stock owned by such holder plus the number of Shares owned by DIHC and PGGM and
their respective Affiliates.

        7.9   AMENDED AND RESTATED BYLAWS. From the date of adoption of the
Amended Bylaws until the third anniversary of such date, PGGM and DIHC agree not
to vote, and to use their commercially reasonable efforts to cause the PGGM
Directors not to vote, to repeal or amend the Amended Bylaws, where such
amendment is covered by Section 10.01(b) of such Amended Bylaws, unless such
amendment is approved by the Wilson Directors (as defined in the Amended
Bylaws).

        8.    STANDSTILL. During the Standstill Period, any Holder that together
with its Affiliates owns 25% or more of the issued and outstanding shares of
Common Stock shall not:

        (a) directly or indirectly, purchase or otherwise acquire, or propose or
offer to purchase or otherwise acquire, any Equity Securities whether by tender
offer, market purchase, 

<PAGE>

privately negotiated purchase, Business Combination or otherwise, if,
immediately after such purchase or acquisition, the Holder Interest of such
Holder would equal or exceed the Initial Percentage;

        (b) directly or indirectly propose to the Company or any Person a
Business Combination;

        (c) make, or in any way participate, directly or indirectly, in any
"solicitation" of "proxies" to vote (as such terms are used in the rules
promulgated by the Commission under Section 14(a) of the Exchange Act) or seek
to advise, encourage or influence any person or entity with respect to the
voting of any shares of capital stock of the Company, initiate, propose or
otherwise solicit stockholders of the Company for the approval of one or more
stockholder proposals or induce or attempt to induce any other Person to
initiate any stockholder proposal; or

        (d) deposit any Equity Securities into a voting trust or subject any
Equity Securities to any arrangement or agreement with respect to the voting of
such securities or form, join or in any way participate in a "group" (within the
meaning of Section 13(d)(3) of the Exchange Act) with respect to any Equity
Securities, other than as expressly set forth in Section 7 hereof.

        Nothing in this Section 8 shall limit the ability of PGGM Directors to
function in their capacities as members of the Board. The provisions of this
Section 8 may be waived by the Company only upon the approval of a majority of
the Board, excluding all PGGM Directors and shall not be applicable to actions
approved by the majority of the Board, excluding all PGGM Directors in
circumstances in which the PGGM Directors are "interested directors" under
Section 78.140 of the Nevada General Corporation Law.

     9. ASSIGNMENT. This Agreement shall not be assignable by the parties 
hereto, except (I) by PGGM, DIHC or any Holder pursuant to a transfer of 
Shares permitted hereunder to a Permitted Transferee that agrees in writing 
to be bound by the terms hereof (including, without limitation, Section 7.5 
and 8, if applicable) and (II) the rights to cause the Company to register 
Shares pursuant to Section 3 may be assigned by PGGM, DIHC or any Holder, but 
only together with all obligations of Holders under Section 3 and Section 
7.4, to a transferee of Shares representing at least 1% of the issued and 
outstanding shares of Common Stock, PROVIDED that, within a reasonable time 
after such transfer, the Company is furnished with written notice of the name 
and address of such transferee or assignee and the securities with respect to 
which such registration rights are being assigned. Notwithstanding any 
transfer of Shares in connection with an assignment permitted by this Section 
9, the transferor shall comply with the obligations set forth in Section 2 
hereof.

     10. MISCELLANEOUS. This Agreement constitutes the sole understanding of the
parties hereto with respect to the subject matter hereof; PROVIDED, HOWEVER,
that this provision is not intended to abrogate any other written agreement
between or among the parties executed with or after this Agreement or any
written agreement pertaining to another subject matter. No 

<PAGE>

amendment of this Agreement shall be binding unless made in writing and duly
executed by the parties hereto. This Agreement shall be construed in accordance
with and governed by the laws of the State of New York without regard to
conflict of laws principles thereof. No provision of this Agreement shall be
construed against or interpreted to the disadvantage of any party hereto by any
court or other governmental or judicial authority or by any board of arbitrators
by reason of such party or its counsel having or being deemed to have structured
or drafted such provision. Unless otherwise expressly provided herein, all
references in this Agreement to Section(s) shall refer to the Section(s) of this
Agreement. The headings in this Agreement are for purposes of reference only and
shall not limit or otherwise affect the meaning of this Agreement. This
Agreement may be executed in any number of counterparts, each of which shall be
an original, but all of which together shall constitute one instrument.

     11. NOTICES. All notices, requests, claims, demands and other 
communications hereunder shall be in writing and shall be given or made (and 
shall be deemed to have been duly given or made upon receipt) by delivery in 
person, by courier service, by cable, by telecopy, by telegram, by telex or 
by registered or certified mail (postage prepaid, return receipt requested) 
to the respective parties at the following addresses (or at such other 
address for a party as shall be specified in a notice given in accordance 
with this Section 11):

        (a) IF TO PGGM:           Pensioenfonds PGGM
                                  Kroostweg-Noord 149
                                  3704 DV Zeist
                                  The Netherlands
                                  P. O. Box 117
                                  3700 AC Zeist
                                  The Netherlands
                                  Telecopy: 011 (31.30) 696-3388
                                  Attention:  Mr. Jan van der Vlist
                                              Ms. Anneke C. van de Puttelaar

            WITH A COPY TO:       Richards & O'Neil, LLP
                                  885 Third Avenue
                                  New York, New York 10022-4873
                                  Telecopy: (212) 750-9022
                                  Attention:  Robert M. Safron, Esq.

        (b) IF TO DIHC:           200 Galleria Parkway, NW
                                  Suite 2000
                                  Atlanta, Georgia 30339
                                  Telecopy: (770) 951-9349
                                  Attention:  Mr. Craig Johnston

            WITH A COPY TO:       Richards & O'Neil, LLP
                                  885 Third Avenue

<PAGE>

                                  New York, New York 10022-4873
                                  Telecopy: (212) 750-9022
                                  Attention:  Robert M. Safron, Esq.

        (c) IF TO THE COMPANY:    126 East 56th Street
                                  New York, New York 10022
                                  Telecopy: (212) 605-7199
                                  Attention:  Mr. John S. Moody

            WITH A COPY TO:       King & Spalding
                                  191 Peachtree Street, NE
                                  Atlanta, Georgia 30303
                                  Telecopy: (404) 572-5148
                                  Attention:  William B. Fryer, Esq.

        (d) If to any other Holder to the address set forth in the notice
referred to in Section 9 hereof.

     12. REMEDY. In the event that the Company materially breaches its
obligations to PGGM under Sections 7.1 and 7.2 hereof and such breach continues
for a period of 30 days after PGGM gives the Company written notice of such
breach, the obligations of PGGM under Sections 7.4, 7.5 and 8 shall thereafter
be suspended for such period of time as such breach continues; PROVIDED,
HOWEVER, that upon any such breach being cured by the Company or waived by PGGM,
PGGM shall again be obligated to comply with the provisions of Sections 7.4, 7.5
and 8.

     13. THIRD PARTY BENEFICIARY. The parties to this Agreement agree and
acknowledge that Wilson III or the Wilson Designee are intended beneficiaries of
the provisions of Sections 7.1(d) and 7.9 of this Agreement, and Wilson III and
the Wilson Designee shall have the rights of intended beneficiaries to enforce
such provisions.

<PAGE>

        IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed and delivered as of the date first above written.

                                        CORNERSTONE PROPERTIES INC.


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




                                        DUTCH INSTITUTIONAL HOLDING
                                        COMPANY, INC.


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




                                        STICHTING PENSIOENFONDS VOOR DE 
                                        GEZONDHEID, GEESTELIJKE EN 
                                        MAATSCHAPPELIJKE BELANGEN


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



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



        [Signature Page to Amended and Restated Registration Rights and
                                Voting Agreement]

<PAGE>

                                    EXHIBIT A
                                    ---------
                                       TO
                              AMENDED AND RESTATED
                    REGISTRATION RIGHTS AND VOTING AGREEMENT




Stockholders' Agreement dated November 22, 1996, between the Company and New
York State Teachers' Retirement System.

Stockholders' Agreement dated November 7, 1996, between the Company and Hexalon
Real Estate, Inc.

Letter Agreement dated July 10, 1995 between the Company and Deutsche Bank AG.

Registration Rights Agreement dated June 3, 1998, by and between the Company and
the parties named therein.

Registration Rights Agreement dated as of January 29, 1998, among the Company
and the Holders identified therein.

Registration Rights Agreement dated as of April 28, 1998, among the Company and
the Holders identified therein.

Registration Rights Agreement dated as of April 28, 1998, among the Company and
The Prudential Insurance Company of America.

Registration Rights and Lockup Agreement dated December 16, 1998, by and between
the Company and the parties named therein.