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                                                                  Exhibit 10.103

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                           SECOND AMENDED AND RESTATED

                             JOINT VENTURE AGREEMENT

                                       OF

                       MARKET SQUARE DEVELOPMENT INVESTORS

                                 By and Between

                          CORNERSTONE MARKET SQUARE LLC

                                       and

                            DIHC MARKET SQUARE, INC.,

                                   dated as of

                               January 30th, 1998

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                                TABLE OF CONTENTS

                                                                            Page
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ARTICLE I

    DEFINED TERMS.............................................................2

ARTICLE II

    THE VENTURE...............................................................6
    Section 2.01      Formation...............................................6
    Section 2.02      Purposes and Scope of the Venture.......................7
    Section 2.03      Assumed Name Certificate................................7
    Section 2.04      Scope of Venturer's Authority...........................7
    Section 2.05      Principal Place of Business.............................7

ARTICLE III

    MANAGEMENT................................................................7
    Section 3.01      Management of the Venture...............................7
    Section 3.02      Execution and Performance of Documents..................8
    Section 3.03      Liability of Managing Partner/Indemnity.................8
    Section 3.04      Compensation and Expenses of Venturers and Venture......8
    Section 3.05      Contracts with Related Parties..........................9

ARTICLE IV

    ACCOUNTING, CONTRIBUTIONS, DISTRIBUTIONS
    AND ALLOCATIONS...........................................................9
    Section 4.01      Percentage Interests of Venturers.......................9
    Section 4.02      Capital Contributions..................................10
    Section 4.03      Optional Loans.........................................13
    Section 4.04      Tax Status and Returns.................................14
    Section 4.05      Distributions..........................................15
    Section 4.06      Allocations of Profits, Gains and Losses...............17
    Section 4.07      Accounting.............................................18
    Section 4.08      Bank Accounts..........................................18
    Section 4.09      Withholding............................................19
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ARTICLE V

    TERM AND TERMINATION.....................................................20
    Section 5.01      Term...................................................20
    Section 5.02      Liquidation and Distribution Procedure.................20
    Section 5.03      Event of Dissolution...................................20
    Section 5.04      Default................................................22
    Section 5.05      Conversion to Limited Partnership......................23

ARTICLE VI

    SALE, ASSIGNMENT, TRANSFER OR OTHER DISPOSITION..........................24
    Section 6.01      Prohibited Transfers...................................24
    Section 6.02      Permitted Transfers....................................24

ARTICLE VII

     BUY-SELL UNDER THE MSA VENTURE AGREEMENT................................26

ARTICLE VIII

    RIGHT OF FIRST OFFER UNDER THE MSA VENTURE AGREEMENT.....................27

ARTICLE IX

    GENERAL..................................................................28
    Section 9.01      Notices................................................28
    Section 9.02      Governing Laws.........................................29
    Section 9.03      Exculpation/Indemnification............................29
    Section 9.04      Entire Agreement.......................................30
    Section 9.05      Waiver.................................................30
    Section 9.06      Severability...........................................30
    Section 9.07      Status Reports.........................................30
    Section 9.08      Appraisals.............................................31
    Section 9.09      Attorneys' Fees........................................31
    Section 9.10      Terminology............................................31
    Section 9.11      Binding Agreement......................................31
    Section 9.12      Additional Remedies....................................31
    Section 9.13      Meetings...............................................31


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    Section 9.14      Partition..............................................32
    Section 9.15      Conflicts with the MSA Venture Agreement and
                      AALP Partnership Agreement.............................32
    Section 9.16.     Conflicts with the DIHC Purchase Agreement.............32

EXHIBIT A    Legal Description of Land


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                           SECOND AMENDED AND RESTATED
                             JOINT VENTURE AGREEMENT
                     FOR MARKET SQUARE DEVELOPMENT INVESTORS

      THIS SECOND AMENDED AND RESTATED JOINT VENTURE AGREEMENT ("Agreement"),
made and entered into as of this 30th day of January, 1998, by and between
CORNERSTONE MARKET SQUARE LLC, a Delaware limited liability company ("C-Stone"),
and DIHC MARKET SQUARE, INC., a Georgia corporation ("DIHC").

      WHEREAS, DIHC and Crow-Pennsylvania Avenue Limited Partnership
("Crow-PALP") previously entered into a District of Columbia general partnership
known as Market Square Associates ("MSA"); and

      WHEREAS, MSA is a limited partner and the managing general partner of
Avenue Associates Limited Partnership ("AALP"), a District of Columbia limited
partnership, which is the owner of certain land on Pennsylvania Avenue in the
District of Columbia and all improvements thereon generally known as "Market
Square"; and

      WHEREAS, DIHC subsequently sold and conveyed to DIHC-Pennsylvania Avenue,
Inc. ("DIHC-Pennsylvania") 41-2/3% of the interest of DIHC in MSA; and

      WHEREAS, pursuant to that certain Joint Venture Agreement dated January
27, 1989 (the "Original Venture Agreement"), DIHC and DIHC-Pennsylvania formed a
District of Columbia general partnership known as Market Square Development
Investors (the "Original Venture"), and DIHC-Pennsylvania contributed its entire
interest in MSA, and DIHC contributed a portion of its interest in MSA, to the
Original Venture; and

      WHEREAS, immediately following the execution and delivery of the Original
Venture Agreement, M.I. West Pennsylvania Limited Partnership ("M.I.
Pennsylvania") purchased from DIHC-Pennsylvania all of the right, title and
interest of DIHC-Pennsylvania in and to the Original Venture, and
contemporaneously therewith DIHC and M.I. Pennsylvania entered into that certain
Joint Venture Agreement dated January 27, 1989 (the "Amended Venture Agreement")
for the Original Venture, which Amended Venture Agreement amended and restated
the Original Venture Agreement; and

      WHEREAS, prior to the execution and delivery of this Agreement, C-Stone
made a capital contribution to, and was admitted as a venturer in, the Original
Venture and the Original Venture redeemed the interest of M.I. Pennsylvania in
the Original Venture; and

      WHEREAS, immediately following the redemption of the interest of M.I.
Pennsylvania in the Original Venture and immediately prior to the execution and
delivery of this Agreement, C-Stone made a loan to the Original Venture, and the
Original Venture redeemed all but one percent (1%) of the interest of DIHC in
the Original Venture; and
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      WHEREAS, C-Stone and DIHC desire to amend and restate the Amended Venture
Agreement in order to set forth their respective rights, obligations and
relationships to one another with respect to MSA and AALP.

                              W I T N E S S E T H:

      In consideration of the mutual covenants set forth herein, and for other
good and valuable consideration in hand paid, by each party to the other,
receipt of which is hereby acknowledged, the parties hereto agree as follows:

                                    ARTICLE I

                                  DEFINED TERMS

      As used herein, the following terms shall have the following meanings:

            1.01. AALP. The term "AALP" shall mean Avenue Associates Limited
Partnership, a District of Columbia limited partnership.

            1.02. AALP Partners. The term "AALP Partners" shall mean MSA and
WALP and their permitted successors and assigns from time to time as partners in
AALP.

            1.03. AALP Partnership Agreement. The term "AALP Partnership
Agreement" shall mean the Third Amended and Restated Agreement of Limited
Partnership of AALP dated as of July 15, 1987, as the same may be amended or
restated from time to time.

            1.04. AALP Partnership Property. The term "AALP Partnership
Property" shall mean the Land, the Improvements and all other assets of AALP.

            1.05. Additional Ordinary Capital Contribution. The term "Additional
Ordinary Capital Contribution" shall mean the additional cash amounts
contributed by the Venturers to the Venture pursuant to Section 4.02(a).

            1.06. Affiliate. The term "Affiliate" shall mean, as to any Person,
(i) any other Person directly or indirectly controlling, controlled by or under
common control with such Person; (ii) the officers, directors or partners of
such Person; and (iii) if such Person is an officer, director or partner, any
company for which such Person acts in any such capacity. For purposes of this
definition the term "control" means the ownership of 10% or more of the
beneficial or voting interest in the Person referred to.


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            1.07. Amended Venture Agreement. The term "Amended Venture
Agreement" shall mean the Joint Venture Agreement of Market Square Development
Investors, dated January 27, 1989 between DTHC and M.I. Pennsylvania.

            1.08. Approved by the Venturers or Approval by (or of) the
Venturers. The term "Approved by the Venturers" or "Approval by (or of) the
Venturers shall mean approved in writing in advance by all Venturers in their
sole and absolute discretion.

            1.09. Assignment and Assumption Agreement. The term "Assignment and
Assumption Agreement" shall have the meaning assigned to such term in Section
4.02(a)(iii).

            1.10. Buffer Loan. The term "Buffer Loan" shall have the meaning set
forth in the MSA Venture Agreement.

            1.11. Capital Account. The term "Capital Account" shall mean the
accounts maintained for each Venturer as set forth in Section 4.01.

            1.12. Closing Date. The term "Closing Date" means the date of
C-Stone's admission as a Venturer in the Venture, which is the date of this
Agreement.

            1.13. Code. The term "Code" shall mean the United States Internal
Revenue Code of 1986, as amended, and any successor statute thereto.

            1.14. Construction/Permanent Loan. The term "Construction/Permanent
Loan" shall have the meaning set forth in the MSA Venture Agreement, which loan
has been assigned to the sole member of C-Stone.

            1.15. Conversion and Conversion Date. The terms "Conversion" and
"Conversion Date" shall have the meaning set forth in the MSA Venture Agreement.

            1.16. Crow-PALP. The term "Crow-PALP" shall mean Crow-Pennsylvania
Avenue Limited Partnership, a Texas limited partnership, and its permitted
successors and assigns, as a partner in MSA.

            1.17. C-Stone Loan. The team "C-Stone Loan" shall mean the recourse
loan made by C-Stone to the Venture immediately prior to the execution and
delivery of this Agreement in the original principal amount of $2,908,230.00,
which loan is evidenced by that certain Promissory Note and Loan Agreement from
the Venture to C-Stone of even date herewith.

            1.18. Defaulting Venturer. The term "Defaulting Venturer" shall have
the meaning assigned to such term in Sections 4.02(c), 4.02(d) and 5.04.


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            1.19. DIHC Finance Loan. The term "DIHC Finance Loan" shall mean the
recourse loan by DIHC Finance Corporation to the Venture in the original
principal amount of up to $41,900,000.00, which loan is evidenced by that
certain Promissory Note and Loan Agreement from the Venture to DIHC Finance
Corporation in said amount dated August 15, 1997, which loan has been assigned
to the sole member of C-Stone.

            1.20. DIHC-Pennsylvania. The term "DIHC-Pennsylvania" shall mean
DIHC-Pennsylvania Avenue, Inc., a Georgia corporation.

            1.21. DIHC Purchase Agreement. The term "DIHC Purchase Agreement"
shall have the meaning assigned to such term in Section 4.02(d).

            1.22. Extraordinary Capital Contribution. The term "Extraordinary
Capital Contribution shall mean the cash amounts contributed by the Venturers to
the Venture pursuant to Section 4.02(b).

            1.23. Gain and Loss. The terms "Gain" and "Loss" shall have the
meanings set forth in Section 4.06(a).

            1.24. Improvements. The term "Improvements" shall mean the mixed use
development generally known as "Market Square" consisting of approximately
850,000 square feet of office, residential and residential and retail/commercial
space located in two 13-story buildings and a parking garage below grade
containing parking spaces for approximately 950 automobiles and any other
improvements from time to time owned by AALP or its successors and assigns as
owner of the Land.

            1.25. Land. The term "Land" shall mean that certain parcel of real
property and the improvements presently located thereon in the District of
Columbia, owned by AALP, and more particularly described in Exhibit A attached
hereto and made a part hereof.

            1.26. Manager. The term "Manager" shall have the meaning set forth
in the MSA Venture Agreement.

            1.27. Managing Partner. The term "Managing Partner," from and after
the date hereof, shall mean C-Stone and its successors and assigns, except as
otherwise provided in Section 5.05(a).

            1.28. Member. The term "Member" shall mean the corporate officer(s)
or general partner(s) or other authorized agent(s), as the case may be, through
whom a Venturer shall act in connection with decisions relating to its interests
in the Venture.

            1.29. MSA. The term "MSA" shall mean Market Square Associates, a
District of Columbia general partnership.


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            1.30. MSA Venture Agreement. The term "MSA Venture Agreement" shall
mean the Joint Venture Agreement for MSA, dated as of May 21, 1987, as amended
from time to time.

            1.31. MSA Venture Property. The term "MSA Venture Property" shall
mean the interest of MSA in AALP, and any other assets of MSA.

            1.32. MSA Venturers. The term "MSA Venturers" shall mean Crow-PALP
and the Venture, and their permitted successors and assigns as ventures in MSA.

            1.33. Net Cash Flow. The term "Net Cash Flow" shall have the meaning
set forth in Section 4.05(a).

            1.34. Non-Defaulting Venturer. The term "Non-Defaulting Venturer"
shall have the meaning assigned that term in Sections 4.02(c), 4.02(d) and 5.05.

            1.35. Offer. The term "Offer" shall have the meaning assigned to
such term in the MSA Venture Agreement.

            1.36. Operating Profits and Operating Losses. The terms "Operating
Profits" and "Operating Losses" shall have the meanings set forth in Section
4.06(a).

            1.37. Optional Loan. The term "Optional Loan" shall have the meaning
set forth in Section 4.03.

            1.38. Original Venture. The Term "Original Venture" shall mean
Market Square Development Investors, a District of Columbia general partnership
formed pursuant to the Original Venture Agreement.

            1.39. Original Venture Agreement. The term "Original Venture
Agreement" shall mean the Joint Venture Agreement of Market Square Development
Investors, dated January 27, 1989 between DIHC and DIHC-Pennsylvania.

            1.40. Percentage Interest. The term "Percentage Interest" shall have
the meaning set forth in Section 4.01(a).

            1.41. Person. The term "Person" shall mean any individual,
partnership, association, corporation or other entity.

            1.42. Property. The term "Property" shall mean the interest of the
Venture as a partner in MSA and all other assets of the Venture.

            1.43. Sales or Refinancing Proceeds. The term "Sales or Refinancing
Proceeds" shall have the meaning set forth in Section 4.05(d).


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            1.44. TMP. The term "TMP" shall mean the tax matters partner as
defined in Section 4.04(c)(i).

            1.45. Transfer. The term "Transfer" shall have the meaning set forth
in Section 6.01.

            1.46. Venture. The term "Venture" shall mean the Original Venture as
formed pursuant to the Original Venture Agreement and modified by the Amended
Venture Agreement, and as further modified pursuant to this Agreement.

            1.47. Venturer or Venturers. The term "Venturer" shall mean C-Stone
or DIHC, individually, and the term "Venturers" shall mean C-Stone and DIHC,
collectively, and each of their permitted successors and assigns under this
Agreement.

            1.48. WALP. The term "WALP" shall mean Western Associates Limited
Partnership, a District of Columbia limited partnership, and its permitted
successors and assigns as a partner in AALP.

            1.49. Terms which are capitalized but not separately defined in this
Agreement shall have the same meanings in this Agreement as in the MSA Venture
Agreement.

            1.50. The recitals set forth above are true and correct, and are
hereby incorporated herein by reference.

                                   ARTICLE II

                                   THE VENTURE

Section 2.01. Formation

      (a) DIHC and DIHC-Pennsylvania formed the Original Venture pursuant to the
Original Venture Agreement, as modified by DIHC and M.I. Pennsylvania pursuant
to the Amended Venture Agreement, for the limited purposes and scope set forth
therein. C-Stone and DIHC hereby agree to amend and restate the terms and
conditions of the Amended Venture Agreement as set forth herein. The Original
Venture, as modified by this Agreement, is hereinafter referred to as the
"Venture". The business and affairs of the Venture shall be conducted solely
under the name "Market Square Development Investors" and such name shall be used
at all times in connection with the Venture's business and affairs.

      (b) Except as expressly herein to the contrary, the rights and obligations
of the Venturers and the administration and termination of the Venture shall be
governed by the Uniform Partnership Act of the District of Columbia.


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Section 2.02. Purposes and Scope of the Venture

      (a) Subject to the provisions of this Agreement, the Venture shall be
limited strictly to the participation as one of the venturers in MSA for all the
purposes set forth in the MSA Venture Agreement.

      (b) Nothing in this Agreement shall be deemed to restrict in any way the
freedom of any Venturer (or any Affiliate of any Venturer) to conduct any other
business or activity whatsoever (including the acquisition, development,
leasing, sale, operation and management of real property) without any
accountability to the Venture or any other Venturer with respect to the income
or profits therefrom or the effect of such activity on the Property or the Land,
even if such business or activity competes with the business of the Venture.

Section 2.03. Assumed Name Certificate

      The Venturers shall execute and file in the appropriate records any
assumed or fictitious name certificate or certificates (or amendments thereof)
required by law to be filed in connection with the formation (or continuation)
of the Venture.

Section 2.04. Scope of Venturer's Authority

      Except as otherwise expressly and specifically provided in this Agreement,
no Venturer shall have any authority to act for, or assume any obligations or
responsibility on behalf of, any other Venturer or the Venture.

Section 2.05. Principal Place of Business

      The principal place of business of the Venture shall be at the office of
C-Stone at 126 East 56th Street, New York, New York 10022, or at such other
place of business as Approved by the Venturers.

                                   ARTICLE III

                                   MANAGEMENT

Section 3.01. Management of the Venture

      Except where herein expressly provided to the contrary, all decisions with
respect to the operation and control of the Venture shall be vested in the
Managing Partner. C-Stone is hereby designated as the Managing Partner of the
Venture and hereby accepts such designation and agrees to discharge all
obligations of the Managing Partner. Except where herein expressly provided to
the contrary, the Managing Partner shall be responsible for the operation and
control of the Venture, for


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making all decisions with respect to the Venture and its interest in MSA, and
the day to day supervision of all aspects of the business of the Venture.

Section 3.02. Execution and Performance of Documents

      Documents to which the Venture is a party (including but not limited to
all documents on behalf of the Venture as an MSA Venturer) shall be executed
and/or performed on behalf of the Venture by the Managing Partner or by an agent
authorized by the Venture or the Managing Partner to execute such documents. No
mortgagee, person, firm, trustee, grantee, partnership, corporation or other
entity shall be required to inquire into said authority of the Venturers or the
Managing Partner to execute and/or perform any document on behalf of the
Venture. Except as otherwise expressly provided in this Agreement, no Venturer
or representative thereof shall have the authority or right to bind or act for
the Venture or any of the other Venturers.

Section 3.03. Liability of Managing Partner/Indemnity

      The Managing Partner shall not be liable or accountable to the Venture or
to the other Venturers, in damages or otherwise, for any error of judgment, for
any mistake of law, or for any other act or thing which it may do or refrain
from doing in connection with the business and affairs of the Venture, except in
the case of (i) intentional misconduct, (ii) a knowing violation of law, or
(iii) bad faith in failing to perform its duties hereunder. The Venture (to the
extent of its assets, but without requiring any additional contribution of
capital by the Venturers) does hereby agree to indemnify and hold the Managing
Partner wholly harmless from any loss, expense or damage suffered by the
Managing Partner by reason of anything it may do or refrain from doing hereafter
for and on behalf of the Venture and in furtherance of the Venture's interests;
provided, however that the Venture shall not be required to indemnify the
Managing Partner for any loss, expense or damage which the Managing Partner may
suffer as a result of (i) intentional misconduct, (ii) a knowing violation of
law, or (iii) bad faith in failing to perform its duties hereunder.

Section 3.04. Compensation and Expenses of Venturers and Venture

      (a) Except as may be expressly provided for herein or in the MSA Venture
Agreement or the AALP Partnership Agreement, no payment will be made by the
Venture to any Venturer for the services of such Venturer or any member,
stockholder director or employee of any Venturer.

      (b) Except as expressly provided herein or in the MSA Venture Agreement or
the AALP Partnership Agreement, no Venturer shall be entitled to any
compensation or reimbursement from the Venture or any other Venturer for
expenses incurred in connection with the formation, business or affairs of the
Venture.

      (c) Notwithstanding any provision of this Agreement to the contrary, the
Managing Partner and the TMP shall be entitled to reimbursement for
out-of-pocket expenses actually incurred on behalf of the Venture, provided only
that (i) the same are reasonable in amount and reasonably necessary or


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appropriate in the Venture's business, and (ii) the same are consistent with the
provisions of this Agreement, the MSA Venture Agreement and/or the AALP
Partnership Agreement.

      (d) The Venture shall pay all legal and other expenses of the Venture or
of any Venturer incurred after the Closing Date, provided such expenses are
reasonable in amount and are of a nature customarily borne by a borrower or a
venturer on transactions of a similar nature; each of the Venturers' legal and
other expenses incurred up to and including the Closing Date shall be borne by
the respective Venturer.

Section 3.05. Contracts with Related Parties

      After the date hereof and except as otherwise provided in Section 3.04, no
Venturer may contract with or employ on behalf of the Venture any person or
entity which is an Affiliate of any Venturer in connection with the performance
of any duties or providing any goods or services to the Venture specified in
this Agreement unless Approved by the Venturers.

                                   ARTICLE IV

            ACCOUNTING, CONTRIBUTIONS, DISTRIBUTIONS AND ALLOCATIONS

Section 4.01. Percentage Interests of Venturers

      (a) Subject only to any changes occurring through the operation of Section
4.02(c)(iii), each Venturer's interest in the Venture ("Percentage Interest")
shall be as follows:

                           C-Stone          99%
                           DIHC              1%

      (b) The Venture shall determine and maintain "Capital Accounts" for each
Venturer throughout the full term of the Venture in accordance with the rules of
Treasury Regulation section 1-704-1(b)(2)(iv), as such regulation may be amended
from time to time. To the extent not inconsistent with such rules, the following
provisions shall apply.

      The Capital Account of each Venturer shall be credited with (1) an amount
equal to such Venturer's cash contributions and the fair market value of
property contributed to the Venture by such Venturer (net of liabilities
securing such contributed property that the Venture is considered to assume or
take subject to under section 752 of the Code) and (2) such Venturer's share of
the Venture's income and gain (or items thereof), including income exempt from
tax. The Capital Account of each Venturer shall be debited by (i) the amount of
cash distributions to such Venturer and the fair market value of property
distributed to such Venturer (net of liabilities assumed by such Venturer and
liabilities to which such distributed property is subject) and (ii) such
Venturer's share of the Venture's losses and


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deductions (or items thereof) and of expenditures which can neither be
capitalized nor deducted for tax purposes.

      (c) In the case of a liquidation of the Venture or of any Venturer's
interest in the Venture, any Property which is not sold, but which is
distributed to one or more Venturers in connection with such liquidation shall
be valued at its then fair market value (determined by agreement of all of the
Venturers or in accordance with the appraisal procedures set forth in Section
9.08 hereof). Such fair market value shall be used to determine the Gain or Loss
which would have been recognized by the Venture if the Property had actually
been sold for its fair market value (subject to any debt secured by the
Property. The excess of such fair market value over the amount of any debt
secured by the Property shall be treated as Sales or Refinancing Proceeds for
purposes of determining the Venturers' rights to distributions pursuant to
Section 4.05. The Capital Accounts of the Venturers shall be adjusted to reflect
the allocation of the deemed Gain or Loss under Section 4.06 (as if the Property
had in fact been sold in such manner and the Gain or Loss which would thereby
have been recognized were in fact recognized) and the distribution of the deemed
Sales or Refinancing Proceeds under Section 4.05.

Section 4.02. Capital Contributions

      (a) Subject to Section 4.02(d), the Venturers shall make the following
Additional Ordinary Capital Contributions to the Venture:

            (i) On or before each date on which the Venture is required to make
a capital contribution to MSA pursuant to the MSA Venture Agreement, each
Venturer shall contribute to the Venture cash in an amount equal to its
Percentage Interest multiplied by the amount the Venture is required to
contribute to MSA on such date.

            (ii) On or before the date on which the Venture is required to make
a Buffer Loan advance to MSA pursuant to the MSA Venture Agreement, each
Venturer shall contribute to the venture cash in an amount equal to its
Percentage Interest multiplied by the amount the Venture is required to advance
to MSA on such date as a Buffer Loan.

            (iii) On or before the date the Venture is required to pay any
payments of the "Incentive Fee" (as defined in the Incentive Management
Agreement dated July 15, 1987 between Crow-PALP and DIHC) as required under the
Assignment and Assumption Agreement dated January 27, 1989 between the Venture
and DIHC (the "Assignment and Assumption Agreement"), each Venturer shall
contribute to the Venture cash in an amount equal to its Percentage Interest
multiplied by the total amount the Venture is required to pay on such date.

            (iv) The contributions made to the Venture (a) under paragraph (i)
of this Section 4.02(a) shall be used by the Venture to satisfy its obligation
to make the capital contributions to MSA required of the Venture under the MSA
Venture Agreement; (b) under paragraph (ii) of this Section 4.02(a) shall be
used by the Venture to satisfy its obligation to make advances of the Buffer
Loan to


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MSA as required under the MSA Venture Agreement; and (c) under paragraph (iii)
of this Section 4.02(a) shall be used by the Venture to satisfy its obligation
to make the Incentive Fee payments required of the Venture under the Assignment
and Assumption Agreement.

            (v) If Additional Ordinary Capital Contributions are required from
the Venturers in accordance with this Section 4.02(a), the Managing Partner
shall (or if the Managing Partner shall fail to do so, any Venturer may) send a
notice thereof to the other Venturers in the manner provided by Section 9.01 of
this Agreement, setting forth the amount of additional capital required in a
report from the Managing Partner or such Venturer, as the case may be, stating
the reasons therefor. Each Venturer shall, within fourteen (14) days of the
receipt of such notice, deposit cash in the amount of the Additional Ordinary
Capital Contribution required of it by such notice in an escrow account with a
bank designated by the Managing Partner pursuant to an escrow agreement Approved
by the Venturers (provided, however, if C-Stone is funding the Additional
Ordinary Capital Contribution on behalf of DIHC pursuant to Section 4.02(d)
below, then the escrow agreement need only be approved by C-Stone), and after
all the required Additional Ordinary Capital Contributions have been made by all
of the Venturers, such funds shall be released for the purposes intended.

            (b) (i) The Venturers shall have no further obligation to contribute
additional capital to the Venture except to the extent the Venture elects (A) to
contribute additional capital to MSA or (B) to raise additional capital for
other purposes and either (A) or (B) is Approved by the Venturers. Any capital
contribution required under this Section 4.02(b)(i) shall be referred to as an
Extraordinary Capital Contribution and shall, subject to Section 4.02(d), be
made by the Venturers in proportion to their respective Percentage Interests.

            (ii) If Extraordinary Capital Contributions are required from the
Venturers in accordance with Section 4.02(b)(i), the Managing Partner shall (or
if the Managing Partner shall fail to do so, any Venturer may) send a notice
thereof to the other Venturers in the manner provided by Section 9.01 of this
Agreement setting forth the amount of additional capital required and a report
from the Managing Partner or such Venturer, as the case may be, stating the
reasons therefor. Each Venturer shall, within fourteen (14) days of the receipt
of such notice, deposit cash in the amount of the Extraordinary Capital
Contribution required of it by such notice in an escrow account with a bank
designated by the Managing Partner pursuant to an escrow agreement Approved by
the Venturers (provided, however, if C-Stone is funding the Extraordinary
Capital Contribution on behalf of DIHC pursuant to Section 4.02(d) below, then
the escrow agreement need only be approved by C-Stone), and after all the
required Extraordinary Capital Contributions have been made by all of the
Venturers, such funds shall be released for the purposes intended.

            (c) In the event that any Venturer fails to make an Additional
Ordinary Capital Contribution in the amount required of such Venturer under
Section 4.02(a) within the time period specified in Section 4.02(a)(v), or fails
to make an Extraordinary Capital Contribution in the amount required of such
Venturer under Section 4.02(b)(i) within the time period specified in Section
4.02(b)(ii), the Managing Partner shall (or, if the Managing Partner shall fail
to do so, any Venturer may) send an additional notice to such Venturer setting
forth the amount unpaid, and the Venturer


                                      -11-
<PAGE>

which has not deposited its Additional Ordinary Capital Contribution or its
Extraordinary Capital Contribution shall have a further period of five (5) days
to make such Additional Ordinary Capital Contribution or Extraordinary Capital
Contribution. If such Additional Ordinary Capital Contribution or Extraordinary
Capital Contribution has not been made as of the end of such five (5) day
period, the Venturer who has failed to make the Additional Ordinary Capital
Contribution or Extraordinary Capital Contribution required of it under Section
4.02(a) or (b), as the case may be, shall be a "Defaulting Venturer". In such
event, each of the Venturers who has made its Additional Ordinary Capital
Contribution or Extraordinary Capital Contribution (a "Non-Defaulting Venturer")
shall have the right to:

            (i) withdraw any Additional Ordinary Capital Contribution or
Extraordinary Capital Contribution made by it pursuant to Section 4.02(a) or
(b), as the case may be, from the escrow account provided therefor and seek the
remedies set forth in Section 5.05; or

            (ii) advance, as a loan to the Defaulting Venturer, the amount of
the Additional Ordinary Capital Contribution or Extraordinary Capital
Contribution required of the Defaulting Venturer (to be contributed as such
Defaulting Venturer's Additional Ordinary Capital Contribution or Extraordinary
Capital Contribution, as the case may be) and seek the remedies set forth in
Section 5.05. The amount advanced as a loan hereunder shall be repayable on
demand and shall bear interest at the rate of twenty-four percent (24%) per
annum, compounded monthly, but in no event at a rate of interest which exceeds
the maximum rate permitted by law; or

            (iii) make the Additional Ordinary Capital Contribution or
Extraordinary Capital Contribution required of the Defaulting Venturer, in which
event the Defaulting Venturer's Percentage Interest shall be decreased at the
rate of one percentage point for each $200,000 of Additional Ordinary Capital
Contribution or Extraordinary Capital Contribution, as the case may be, which
the Defaulting Venturer failed to make (except that its Percentage Interest
shall not be decreased below one percent (1%)); and the Percentage Interest of
the Non-Defaulting Venturer shall be increased by the same number of percentage
points, so that the total Percentage Interests continues to equal one hundred
percent (100%).

            (d) Notwithstanding anything to the contrary contained in
subsections (b) through (d) of this Section 4.02, each of the Venturers
acknowledges and agrees that Cornerstone Properties Inc. ("Cornerstone"), an
Affiliate of C-Stone, has entered into that certain Redemption and Acquisition
Agreement, dated as of October 27, 1997, with the Venture, Dutch Institutional
Holding Company, Inc. and DIHC (the "DIHC Purchase Agreement"), and that,
pursuant to the terms of such agreement Cornerstone or its Affiliates may
purchase the remaining interest of DIHC in the Venture (the "Cornerstone
Purchase Option"). The DIHC Purchase Agreement provides that DIHC shall have no
obligation to fund its proportionate share of any Additional Ordinary Capital
Contributions or Extraordinary Capital Contributions, and shall be relieved and
released from any such obligation, unless the transactions contemplated by the
DIHC Purchase Agreement do not close for any reason other than a default by
Cornerstone thereunder. The Venturers therefore agree that until such time as
the DIHC Purchase Agreement has terminated pursuant to its terms or otherwise
without the Cornerstone


                                      -12-
<PAGE>

Purchase Option having been consummated, other than by reason of a default by
Cornerstone thereunder, C-Stone will make all Additional Ordinary Capital
Contributions and Extraordinary Capital Contributions required to be made by
DIHC pursuant to this Section 4.02, and C-Stone shall further indemnify and hold
harmless DIHC and its respective affiliates, successors and permitted assigns
from any cost, claim, liability, damage or expense (including, but not limited
to, any reasonable attorneys' fees and disbursements) relating to the failure of
C-Stone to make any such Capital Contributions. In the event the DIHC Purchase
Agreement terminated pursuant to its terms or otherwise without the Cornerstone
Purchase Option having been consummated, other than by reason of a default by
Cornerstone thereunder, then within thirty (30) days of such termination, DIHC
shall reimburse to C-Stone the amount of all Additional Ordinary Capital
Contributions and Extraordinary Capital Contributions made by C-Stone on DIHC's
behalf pursuant to this Section 4.02(d). In the event DIHC shall fail to
reimburse the amount of any such Additional Ordinary Capital Contribution or
Extraordinary Capital Contribution as required in this Section 4.02(d), then
DIHC shall be deemed a "Defaulting Venturer," and C-Stone shall have the right
to:

            (i) withdraw any such Additional Ordinary Capital Contribution or
Extraordinary Capital Contribution made by it on the Defaulting Venturer's
behalf from the capital of the Venture, and seek the remedies set forth in
Section 5.05 below; or

            (ii) consider the amount of the Additional Ordinary Capital
Contribution or Extraordinary Capital Contribution made by it on behalf of the
Defaulting Venturer as a loan, and seek the remedies set forth in Section 5.05
below. The amount considered as a loan hereunder shall be repayable on demand,
and shall bear interest at the rate of twenty-four percent (24%) per annum,
compounded monthly, but in no event at a rate of interest which exceeds the
maximum rate permitted by law.

Section 4.03. Optional Loans

      In the event that the Managing Partner determines that certain costs of
the Venture should be funded with loans from the Venturers, then the Managing
Partner may advance to the Venture a loan (hereinafter referred to as an
"Optional Loan") in such amount and on such terms as are acceptable to the
Managing Partner. Prior to advancing any Optional Loan, the Managing Partner
shall notify the other Venturer(s) of its intent to make such advance (at least
five (5) days prior to the date of such advance), and at any time within such
period, the other Venturer(s) may elect to participate in making the Optional
Loan. In the event the other Venturer(s) so elects to participate, such Venturer
shall advance its pro rata share, based upon its Percentage Interest. Principal
and interest of any Optional Loan shall be repayable solely from Net Cash Flow
or Sales or Refinancing Proceeds as provided in Section 4.05. In the event there
is more than one Optional Loan, the loans shall have priority and be repayable
on the basis of the oldest Optional Loan having the first priority. If more than
one of the Venturers have participated in an Optional Loan, then as among such
Venturers, repayments of the principal and interest of the Optional Loans shall
be made pari passu in accordance with the Percentage Interests of such
participating Venturers.


                                      -13-
<PAGE>

Section 4.04. Tax Status and Returns

      (a) Notwithstanding any provisions hereof to the contrary, each of the
Venturers hereby recognizes that the Venture will be a partnership for United
States federal income tax purposes and that the Venture will be subject to all
provisions of Subchapter K of Chapter 1 of Subtitle A of the Code; provided,
however, that the filing of U.S. Partnership Returns of Income shall not be
construed to extend the purposes of the Venture or expand the obligations or
liabilities of the Venturers. At the request of any Venturer, the Venture shall
file an election under section 754 of the Code.

      (b) The Managing Partner shall prepare or cause to be prepared at the
expense of the Venture all tax returns and statements, if any, which must be
filed on behalf of the Venture regarding this transaction and the operation,
dissolution and liquidation of the Venture with any taxing authority, and shall
submit such returns and statements to all of the Venturers for their prior
approval at least thirty (30) days before such returns and statements are due
(including extensions), and when Approved by the Venturers, Make timely filing
thereof. In addition, within one hundred twenty (120) days after the end of each
fiscal year of the Venture, the Managing Partner shall furnish each Venturer
with a report setting forth in sufficient detail all data and information
regarding the business and affairs of the Venture as shall enable the Venture
and each Venturer to prepare its federal, state and local tax returns.

      (c) (i) C-Stone is designated as tax matters partner (herein "TMP") as
defined in section 6231(a) (7) of the Code and the Venturers will take such
actions as may be necessary, appropriate, or convenient to effect the
designation of C-Stone as TMP. In the event that C-Stone shall no longer be the
Managing Partner, then the Venturers shall appoint a new TMP for all taxable
years beginning with the year during which C-Stone ceases to be the Managing
Partner. The TMP and the other Venturers shall use their best efforts to comply
with the responsibilities outlined in this section and in sections 6222 through
6231 of the Code (including, any Treasury Regulations promulgated thereunder).
In determining the TMP's responsibilities under section 6223(g) of the Code, the
term "each partner" shall be deemed to mean "each Venturer".

            (ii) Each of the Venturers shall furnish the TMP with such
information as the TMP may reasonably request to permit it to provide the
Internal Revenue Service with sufficient information to allow proper notice to
the parties in accordance with section 6223 of the Code.

            (iii) No Venturer shall file, pursuant to section 6227 of the Code,
a request for an administrative adjustment of partnership items for any
partnership taxable year without first notifying the other Venturers. If the
other Venturers agree with the requested adjustment, the TMP shall file the
request for administrative adjustment on behalf of the Venture. If the Venturers
do not reach agreement within thirty (30) days or within the period required to
timely file the request for administrative adjustment, if shorter, any Venturer
may file a request for administrative adjustment on its own behalf. If, under
section 6227 of the Code, a request for administrative adjustment which is to be
made by the TMP must be filed on behalf of Venture, the TMP shall also file such
a request on behalf of the Venture under the circumstances set forth in the
preceding sentence.


                                      -14-
<PAGE>

            (iv) If any Venturer intends to file a petition under section 6226
or 6228 of the Code with respect to any partnership item or other tax matter
involving the Venture, the Venturer so intending shall notify the other
Venturers of such intention and the nature of the contemplated proceeding. Such
notice shall be given in a reasonable time to allow the other Venturers to
participate in the choosing of the forum in which such petition will be filed.
If the Venturers do not agree on the appropriate forum, the petition shall be
filed with the United States Tax Court. If any Venturer intends to seek review
of any court decision rendered as a result of the proceeding instituted under
the preceding part of this subsection, such party shall notify the others of
such intended action.

            (v) The TMP shall not bind the other Venturers to a settlement
agreement without the Approval of the Venturers. If any Venturer enters into a
settlement agreement with the Secretary of the Treasury with respect to any
partnership items, as defined by section 6231(a)(3) of the Code, it shall notify
the other Venturers of such settlement agreement and its terms within thirty
(30) days from the date of settlement.

            (vi) These provisions shall survive the termination of the Venture
or the termination of any Venturer's interest in the Venture and shall remain
binding on the Venturers for a period of time necessary to resolve with the
Internal Revenue Service or the Department of the Treasury any and all matters
regarding the Federal income taxation of the Venture and each of the Venturers
with respect to Venture matters.

Section 4.05. Distributions

      (a) The Net Cash Flow of the Venture shall be computed in accordance with
accepted cash basis accounting principles, consistently applied and shall
consist of the excess, if any, of the sum of items (i) and (ii) below over the
sum of items (iii) and (iv) below;

            (i) distributions to the Venture from MSA of Cash Flow (as defined
in the MSA Venture Agreement); plus

            (ii) any other income derived by the Venture other than
distributions to the Venture from MSA of Net Proceeds from a Capital Transaction
(as defined in the MSA Venture Agreement) or by reason of a sale or other
disposition of its interest in MSA; over

            (iii) expenses of the Venture attributable to the income
described in items (i) or (ii) above; plus

            (iv) a reserve for future expenses of the Venture as determined by
the Managing Partner.

      (b) Sales or Refinancing Proceeds of the Venture shall consist of the
excess of the sum of items (i) and (ii) below over item (iii) below;


                                      -15-
<PAGE>

            (i) distributions to the Venture from MSA of Net Proceeds from a
Capital Transaction (as defined in the MSA Venture Agreement); plus

            (ii) net proceeds of a sale or other disposition of the Venture's
interest in MSA; over

            (iii) expenses of the Venture attributable to the items of income
described in (i) or (ii) above.

      (c) Unless otherwise Approved by the Venturers, except as provided in
Sections 4.05(d) or 4.05(e) below, the Net Cash Flow or Sales or Refinancing
Proceeds of the Venture shall be distributed promptly after receipt thereof by
the Venture in the following manner and order of priority:

            (i) First, to repayment of any interest then accrued and deferred
under the DIHC Finance Loan;

            (ii) Next, to repayment of any Installment Payments (as defined in
the Promissory Note and Loan Agreement evidencing the DIHC Finance Loan) then
due under the DIHC Finance Loan;

            (iii) Next, to repayment of the then outstanding principal balance
of the DIHC Finance Loan;

            (iv) Next, to repayment of any interest then accrued and deferred
under the C-Stone Loan;

            (v) Next, to repayment of any Installment Payments (as defined in
the Promissory Note and Loan Agreement evidencing the C-Stone Loan) then due
under the C-Stone Loan;

            (vi) Next, to repayment of the then outstanding principal balance of
the C-Stone Loan; and

            (vii) Thereafter, the remaining Net Cash Flow or Sales or
Refinancing Proceeds shall be distributed to the Venturers in proportion to
their respective Percentage Interests.

      (d) Notwithstanding the provisions of Section 4.05(c), in the event
C-Stone has made Additional Ordinary Capital Contributions or Extraordinary
Capital Contributions on behalf of DIHC under Section 4.02(d), the portion of
the Net Cash Flow or Sales or Refinancing Proceeds that would, under such
Section 4.05(c), be distributed to DIHC shall instead be distributed to C-Stone
until C-Stone has recovered the amount of such contributions from such
distributions or from DIHC pursuant to the terms of such Section 4.02(d).


                                      -16-
<PAGE>

      (e) Notwithstanding the provisions of Section 4.05(c), in the event a
Venturer is a Non-Defaulting Venturer who makes a loan to a Defaulting Venturer
under Section 4.02(c)(ii) or 4.02(d)(ii), the portion of the Net Cash Flow or
Sales or Refinancing Proceeds that would, under such Section 4.05(c), be
distributed to the Defaulting Venturer shall instead be distributed to the
Non-Defaulting Venturer who made such loan until the Non-Defaulting Venturer has
recovered such loan with interest thereon as provided in Section 4.02(c)(ii) or
4.02(d)(ii) from such distributions or from the Defaulting Venturer. Any such
distributions shall be treated as having been made to the Defaulting Venturer to
the Non-Defaulting Venturer on account of such loan.

      (f) Anything in this Agreement to the contrary notwithstanding, in the
event of a liquidation of the Venture, the proceeds of such liquidation
remaining after the payment of or provision for the debts and liabilities of the
Venture shall be applied in accordance with the following order of priority:

            (i) First, to the payment of the expenses of liquidation;

            (ii) Next, to the setting up of any reserves which the liquidating
Venturer may deem necessary or appropriate for any contingent or unforeseen
liabilities or obligations of the Venture (said reserves may be transactions
referred by the remaining Venturer to a bank or trust company acceptable to the
remaining Venturer, as escrowee, to be held by it for distributing such reserves
in payment of any of the aforementioned liabilities or obligations) and at the
expiration of such period as the remaining Venturer shall deem advisable,
distributing the balance, if any, thereafter remaining in the manner provided
herein;

            (iii) Thereafter, to the Venturers in accordance with the provisions
of Section 4.05(c).

            Notwithstanding the prior provisions of this Section 4.05(f), upon
the liquidation of the Venture or any Venturer's interest in the Venture, the
distributions to a Venturer shall not exceed the positive balance in such
Venturer's Capital Account after giving effect to all allocations to such
Venturer under Section 4.06 of Operating Profits, Operating Losses, and Gain and
Loss on the sale or other disposition of the Property (including the allocation
of deemed Gain or Loss pursuant to the provisions of Section 4.01(c)). For
purposes of this provision, the term "liquidation" shall have the meaning given
in the first two sentences of Treasury Regulation section 1. 704-1(b)(2)(ii)(g).

Section 4.06 Allocations of Profits, Gains and Losses

      (a) "Operating Profits" and "Operating Losses" mean the net income and net
loss, respectively, of the Venture, as determined for federal income tax
purposes, but computed without regard to Gain or Loss. "Gain" and "Loss" means
the gain and loss, respectively, as determined for federal income tax purposes,
realized by the Venture from the sale or other disposition of all or any portion
of the Property other than stocks, securities, or cash equivalents held for
investment by the Venture, and Gain or Loss allocated to the Venture by MSA.


                                      -17-
<PAGE>

      (b) All Operating Profits and Operating Losses for any year of the Venture
or portion thereof, and any Gain or Loss, shall be allocated to the Venturers in
proportion to their respective Percentage Interests.

Section 4.07. Accounting

      (a) The fiscal year of the Venture shall be the calendar year.

      (b) The Managing Partner shall cause the Venture to maintain true and
correct books and records of the Venture in accordance with generally accepted
accounting principles, consistently applied, showing all costs, expenditures,
receipts, assets and liabilities and profits and losses and all other records
necessary, convenient or incidental to accurately record the business and
affairs of the Venture. The books of account of the Venture shall be kept and
maintained at all times at the Venture's or the Managing Partner's principal
place of business. The books of account shall be maintained on an accrual basis
of accounting and such method of accounting shall be used for federal income tax
reporting purposes.

      (c) The Managing Partner shall from time to time designate an independent
firm of certified public accountants (the "Accountant") to review and audit the
books and records of the Venture. Within thirty (30) days after the necessary
information is made available to it, the Managing Partner shall deliver to the
Accountant the information necessary to prepare an audited balance sheet and
related audited statement of income or loss for the Venture for the prior fiscal
year. Thereafter, the Managing Partner shall respond to any additional inquiries
or provide additional documentation required by the Accountant and will use its
best efforts to cause the Accountant to prepare and furnish to each of the
Venturers, within thirty (30) days after the necessary information is made
available to it, an audited balance sheet of the Venture dated as of the end of
the fiscal year, and a related audited statement of income or loss for the
Venture for such fiscal year. The Managing Partner shall also furnish to the
other Venturer(s) such other reports on the Venture's operations and condition
as may be reasonably requested by such other Venturer(s).

      (d) Each Venturer shall have the right at all reasonable times during
usual business hours upon at least three (3) business days' notice to the
Managing Partner to audit, examine and make copies of or extracts from the books
of account of the Venture. Such right may be exercised through any agent or
employee of such Venturer designated by it or by an independent firm of
certified public accountants designated by such Venturer. Each Venturer shall
bear all expenses incurred in any examination made for such Venturer's account.
In addition, if the Venture can qualify to forego payment of any withholding
taxes by preparing and filing the appropriate forms, the Venture shall prepare
and file such forms.

Section 4.08. Bank Accounts

      Funds of the Venture shall be deposited in an account or accounts of a
type, in form and name, and in such bank or banks designated from time to time
by the Managing Partner.


                                      -18-
<PAGE>

Section 4.09. Withholding

      (a) The Venture shall be entitled to deduct, withhold, and/or pay any and
all future taxes or withholdings, and all liabilities with respect thereto
("Taxes"), to the extent that the Venture in good faith determines that such
deduction or withholding or payment is required by the Code or any rule or
regulation which is currently in effect or which may be promulgated hereafter
("Applicable Law").

      (b) Any Taxes withheld from an actual distribution to a Venturer shall,
for all purposes of this Agreement, be treated as a distribution to such
Venturer of the same type and character as the distribution giving rise to the
withholding obligation.

      (c) Any amount deducted, withheld or paid with respect to a Venturer in
accordance with Section 4.09(a) that is not described in Section 4.09(b),
including but not limited to any amount measured by a Venturer's distributive
share of any Venture item, shall be considered a loan (a "Special Loan") by the
Venture to such Venturer (the "Borrowing Venturer") made on such date. The
Borrowing Venturer shall repay any such Special Loan to the Venture within ten
(10) days after any Venturer delivers a written demand therefor, together with
interest at two (2%) percentage points above the "prime rate" announced from
time to time by Bankers Trust Company (or such other comparable financial
institution selected by the Managing Partner from time to time) from the date
such loan was made until the date of the repayment thereof. In addition to any
other rights of the Venture to enforce its right to receive payment of the
Special Loan, plus any accrued interest thereon, the Venture may deduct from any
actual distribution to be made to a Borrowing Venturer or any amount available
for distribution to a Borrowing Venturer an amount not greater than the
outstanding balance of any Special Loan, plus any accrued interest thereon, as a
payment in total or partial satisfaction thereof. In the event that the Venture
deducts the amount of the Special Loan plus any accrued interest thereon from
any actual distribution or amount available to be distributed, the amount that
was so deducted shall be treated as an actual distribution to the Borrowing
Venturer for all purposes of this Agreement.

      (d) To the extent that any amount described in Section 4.09(c) is treated
as a distribution under the Applicable Law, repayment of the corresponding
principal amount of any Special Loan shall be treated for all purposes of this
Agreement as a Capital Contribution by the Borrowing Venturer to the Venture as
of the date of repayment.

      (e) Notwithstanding paragraph (a) of this Section 4,09, the Venture shall
not withhold any Taxes (or, where appropriate, shall withhold Taxes at a lower
rate than is generally applicable) from amounts attributable to any Venturer who
has provided to the Venture the Prescribed Forms (as defined below) for the
applicable period. The term "Prescribed Forms" shall mean such duly executed
form(s) or statements(s) as may, from time to time, be prescribed by Applicable
Law and that, Pursuant to the applicable provisions of (x) any income tax treaty
between the United States and the country of residence or organization of the
person providing the form(s) or statement(s), (y) the Code or (z) any applicable
rule or regulation, permit the Venture to make payments free of withholding (or,
subject to withholding at a lower rate than is generally applicable).


                                      -19-
<PAGE>

                                    ARTICLE V

                              TERM AND TERMINATION

Section 5.01. Term

      The Venture commenced on January 27, 1989 and shall continue for a term of
seventy-five (75) years or until sooner terminated in accordance with the
provisions of this Article V, which provisions shall not be mutually exclusive,
i.e., the exercise or use of one of the provisions of this Article shall not
preclude the exercise or use of any other provision of this Agreement except as
in this Article V expressly provided. No Venturer shall have the right, and each
Venturer hereby agrees not, to dissolve, terminate or liquidate, or to petition
a court for the dissolution, termination or liquidation of, the Venture except
as provided in this Agreement.

Section 5.02. Liquidation and Distribution Procedure

      In the event of a liquidation and dissolution as a result of the
occurrence of an Event of Dissolution pursuant to Section 5.03 hereof or a
default pursuant to Section 5.04 hereof, the Withdrawing Venturer or the
Defaulting Venturer, as the case may be, shall have no power or authority to
bind the Venture or the other Venturers but shall assist the remaining Venturers
in the dissolution and winding up of the Venture and the distribution of the
assets thereof. Upon such distribution and winding up, the parties hereto shall
be relieved of all obligations hereunder except for obligations, duties or
rights which have not been determined or ascertained as of the date of such
termination and for rights or remedies which a Non-Defaulting Venturer may have
against a Defaulting Venturer in law or equity. The winding up of the Venture
and the termination of the business and affairs of the Venture shall be
conducted by the remaining Venturers. During the period of such winding up, the
business and affairs of the Venture shall be conducted so as to maintain and
preserve the assets of the Venture in a manner consistent with the winding up of
the affairs thereof.

Section 5.03. Event of Dissolution

      (a) The Venture shall not be wound up and terminated by the occurrence of
an Event of Dissolution unless a majority in interest of the remaining Venturers
shall so decide.

      (b) The term "Event of Dissolution" as used hereunder shall mean:

            (i) the death of any natural person who is now or who shall
hereafter become a Venturer;


                                      -20-
<PAGE>

            (ii) the dissolution or termination of any partnership (other than
(x) as a result of a transfer of partnership interests therein permitted by this
Agreement and (y) a dissolution immediately followed by a reconstitution of such
partnership) or corporation which is now or which shall hereafter become a
Venturer;

            (iii) the declaration of any natural person who is now or who shall
hereafter become a Venturer as a lunatic in any judicial proceedings, or a
showing that such Venturer is of unsound mind;

            (iv) the showing by competent medical evidence that any natural
person who is now or who shall hereunder become a Venturer is mentally or
medically unable to perform the duties required of him by the Venture;

            (v) the occurrence of any one of the following events:

                  (1) if any Venturer (hereinafter referred to as the
"Bankruptcy Party") shall file a voluntary petition in bankruptcy or shall be
adjudicated a bankrupt or insolvent, or shall file any petition or answer
seeking any reorganization, arrangement, composition, readjustment, liquidation,
dissolution or similar relief for itself under the present or any future federal
bankruptcy act or any other present or future applicable federal, state or other
statute or law relating to bankruptcy, insolvency or other relief for debtors,
or shall seek or consent to or acquiesce in the appointment of any trustee,
receiver, conservator or liquidator of the Bankrupt Party or of any substantial
part of said party's properties or said party's interest in the Venture (the
term "acquiesce" as used in this Article includes but is not limited to, the
failure to file a petition or motion to vacate or discharge any order, judgment
or decree within thirty (30) days after the date of such order, judgment or
decree); or

                  (2) if a court of competent jurisdiction shall enter an order,
judgment or decree approving a petition filed against the Bankrupt Party seeking
any reorganization, arrangement, composition, readjustment, liquidation,
dissolution or similar relief under the present or any future federal bankruptcy
act or any other present or future applicable federal, state or other statute or
law relating to bankruptcy, insolvency or other relief for debtors, and such
party shall acquiesce in the entry of such order, judgment or decree or such
order, judgment or decree shall remain unvacated or unstayed for an aggregate of
ninety (90) days (whether or not consecutive) from the date of entry thereof, or
any trustee, receiver, conservator or liquidator of such party or of all or any
substantial part of such party's property or interest in the Venture shall be
appointed without the consent or acquiescence of such party and such appointment
shall remain unvacated or unstayed for an aggregate of ninety (90) days (whether
or not consecutive); or

                  (3) if any Venturer shall admit in writing its inability to
pay its debts as they mature; or

                  (4) if any Venturer shall give notice to any governmental body
of insolvency or pending insolvency, or suspension of operations; or


                                      -21-
<PAGE>

                  (5) if any Venturer shall make an assignment for the benefit
of Creditors or take any other similar action for the protection or benefit of
creditors.

      (c) In the event of the occurrence of an Event of Dissolution:

            (i) Provided that the other Venturers have elected to wind up and
terminate the Venture, the Venturer as to whom the Event of Dissolution has
occurred ("Withdrawing Venturer") shall immediately cease to be a Venturer and
to have any right to participate in the management or decision-making processes
of the Venture (provided that the Withdrawing Venturer shall nevertheless be
entitled to continue to receive distributions of Net Cash Flow and liquidation
proceeds and allocations of gain, loss and credit as fully as if such Venturer
were not a Withdrawing Venturer) and the remaining Venturers may send notices of
the dissolution to such persons and entities as the remaining Venturers may deem
appropriate and necessary under the circumstances.

            (ii) The remaining Venturers shall settle the business of the
Venture as expeditiously as its nature will permit and account for the interests
of the Venturers. Such settlement procedure may include, but shall not be
limited to, a purchase by the remaining Venturers of the interest of the
Withdrawing Venturer at a price determined in accordance with an appraisal or
appraisals of the interest of the Withdrawing Venturer made in accordance with
the appraisal procedures set forth in Section 9.08 hereof, a sale of the
Property in accordance with Article 8 hereof, a public sale of all or any part
of the assets of the Venture, a winding up of the Venture, or a petition to a
court of appropriate jurisdiction requesting that such court supervise and
approve a partitioning of the Property.

            (iii) The good will of the Venture (including the name, records and
files) shall belong to and remain solely vested in the Venture.

            (iv) The prior written consent of the remaining Venturers shall be
required prior to any consent to any administration of the Property by any
referee, trustee or court of bankruptcy. The remaining Venturers shall have the
right at all times to continue the business and affairs of the Venture pursuant
to the terms of this Agreement.

            (v) In lieu of dissolution, the remaining Venturers may elect to
convert the Venture to a limited partnership and the Withdrawing Venturer to a
limited partner as provided in Section 5.05.

Section 5.04. Default

      If any Venturer fails to perform any of its obligations hereunder, or
violates the terms of this Agreement (the "Defaulting Venturer"), the other
Venturers (the "Non-Defaulting Venturers") shall have the right to give the
Defaulting Venturer a notice of default (the "Notice of Default") specifically
setting forth the nature of the default and stating that the Defaulting Venturer
shall have a period of twenty (20) days (or such shorter period as set forth in
Section 4.02) to pay any sums of money specified therein as due and owing to the
Venture or to any Venturer and to cure all other defaults


                                      -22-
<PAGE>

within such period, and if the Defaulting Venturer shall fail to pay such sums
of money or cure such other defaults within such period (or, if such other
defaults are not capable of being cured within such period, the Defaulting
Venturer has not commenced in good fath the curing of such other defaults within
such period and does not thereafter prosecute to completion with diligence and
continuity the curing thereof), the Non-Defaulting Venturers shall (in addition
to any other rights under this Agreement, by law or in equity) have the right:

      (a) to bring any proceeding in the nature of specific performance,
injunction or other equitable remedy, it being acknowledged by each of the
Venturers that damages at law may be an inadequate remedy for a default or
threatened breach of this Agreement;

      (b) to bring any action at law by or on behalf of the Venture or the
Non-Defaulting Venturers as may be permitted in order to recover damages;

      (c) to institute such proceedings (including but not limited to the right
to purchase the interest of the Defaulting Venturer at a price determined by
applicable appraisal made in accordance with the appraisal procedures set forth
in Section 9.08) as may be appropriate to secure an accounting and to dissolve,
wind up and terminate the Venture; or

      (d) to convert the Venture to a limited partnership and the Defaulting
Venturer to a limited partner as provided in Section 5.05.

Section 5.05. Conversion to Limited Partnership

      (a) Upon the occurrence of an Event of Dissolution pursuant to Section
5.03 or the occurrence of a default pursuant to Section 5.04 which is not cured
within the time period specified in Section 5.04, then in addition to, and
without excluding the availability of any other remedy hereunder, the remaining
Venturers or the Non-Defaulting Venturers, as the case may be, may elect to
convert the Venture to a limited partnership organized and existing under the
laws of the State of New York or the District of Columbia and to convert the
Withdrawing Venturer or Defaulting Venturer, as the case may be, to a limited
partner therein. If the Withdrawing Venturer or Defaulting Venturer, as the case
may be, is then the Managing Partner of the Venture, then upon such conversion,
(i) the remaining Venturers or Non-Defaulting Venturers, as the case may be,
shall designate a new Managing Partner, and (ii) the former Withdrawing Venturer
or Defaulting Venturer, as the case may be, shall no longer be the Managing
Partner and shall have no right to participate in the management or
decision-making processes of the Venture.

      (b) In the event of any such conversion, the former Withdrawing Venturer
or Defaulting Venturer, as the case may be, agrees to execute, swear to, and
deliver any and all amendments to this Agreement, together with a certificate of
limited partnership in recordable form, in such form and substance as shall be
reasonably specified by the Other Venturers, all within ten (10) days after
demand and notice from the other Venturers. In order to effectuate the
foregoing, each Venturer (effective upon the adjudication, whether by litigation
or by arbitration, whichever is appropriate, of an Event of


                                      -23-
<PAGE>

Dissolution under Section 5.03 or a default under Section 5.04) hereby appoints
the other Venturers as its true and lawful attorneys-in-fact with the full and
complete power and authority in its name and stead to execute, swear to,
deliver, and record any and all such amendments and such certificate. This power
has been given between the parties upon good and adequate consideration; it is a
power coupled with an interest; it is irrevocable; and it shall survive any
death, incapacity, dissolution, or any other event concerning the Venturers.

      (c) Any and all costs and expenses, including, without limitation,
attorneys' fees, recording costs, and other charges and expenses incurred in
connection with the conversion of the Venture to a limited partnership as
described in this Section 5.05, shall be paid in full by the Withdrawing
Venturer or Defaulting Venturer, as the case may be.

                                   ARTICLE VI

                 SALE, ASSIGNMENT, TRANSFER OR OTHER DISPOSITION

Section 6.01. Prohibited Transfers

      Except as provided in Articles V, VI, VII and VIII, no Venturer may sell,
transfer, assign or otherwise dispose of or mortgage, hypothecate, or otherwise
encumber or permit or suffer any encumbrance of all or any part of its or his
interest in the Venture, or cause to be sold, transferred, assigned, disposed
of, mortgaged, hypothecated or otherwise encumbered, all or any part of the
Venture's interest in MSA, or cause to be sold, transferred, assigned, disposed
of, mortgaged, hypothecated or otherwise encumbered, all or any part of MSA's
interest in AALP, whether voluntarily or involuntarily, by operation of law or
otherwise (hereinafter "Transfer") unless approved by the Venturers, and any
attempt so to Transfer any such interest shall be void and shall constitute a
default hereunder by the Venturer attempting to do so.

Section 6.02. Permitted Transfers

      (a) Notwithstanding any other provision of this Agreement to the contrary
but subject to the provisions of Section 6.02(g), each Venturer shall have the
right, without the consent of any other Venturer, to transfer all of its
interest in the Venture to an Affiliate of such Venturer, to any other Venturer,
or to any Affiliate of any other Venturer; provided, however, neither C-Stone
nor any of its Affiliates may consummate the Cornerstone Purchase Option until
the earlier of (i) January 1, 1999, or (ii) such time as a DIHC Transfer (as
defined in Section 6.02(d) below) has been completed.

      (b) To the extent any Venturer is now or hereafter beneficially owned or
controlled, directly or indirectly, by any Person which is publicly traded, the
sale or transfer or other disposition of all or part of the stock in such
publicly traded Person, shall not be considered a prohibited Transfer within the
meaning of this Agreement.


                                      -24-
<PAGE>

      (c) Notwithstanding any provision of this Agreement to the contrary, the
sale, transfer or other disposition by C-Stone of its interest in the Venture to
a limited partnership in which the sole general partner is Cornerstone or an
Affiliate of Cornerstone, shall not be considered a prohibited Transfer within
the meaning of this Agreement.

      (d) Notwithstanding any provision of this Agreement to the contrary, the
sale, transfer or other disposition of the stock of DIHC by Dutch Institutional
Holding Company, Inc., or the sale, transfer or other disposition of the stock
of Dutch Institutional Holding Company, Inc. by Stichting Pensioenfonds Voor de
Gezondheid, Geestelijke en Maatschappelijke Belangen ("PGGM") (in either case, a
"DIHC Transfer"), shall not be considered a prohibited Transfer within the
meaning of this Agreement; provided, however, that any such DIHC Transfer shall
be, and the proposed transferee of any such stock (the "DIHC Transferee") shall
take such stock, subject to the Cornerstone Purchase Option. At least sixty (60)
days prior to any such DIHC Transfer, DIHC shall provide, or cause Dutch
Institutional Holding Company, Inc. or PGGM, as the case may be, to provide,
written notice to C-Stone of the proposed DIHC Transfer and the identity of the
DIHC Transferee, and shall thereafter provide or cause to be provided to C-Stone
such information regarding the DIHC Transferee as C-Stone shall reasonably
request. At any time following its receipt of such notice, C-Stone, or any of
its Affiliates, may exercise the Cornerstone Purchase Option by written notice
to DIHC and the DIHC Transferee, which notice shall set forth the date of
closing of the Cornerstone Purchase Option, which shall be at least sixty (60)
days after the date of such notice, but which in all events shall occur after
the consummation of the DIHC Transfer.

      (e) Any permitted transferee of an interest in the Venture shall become a
Venturer unless the terms of the Transfer expressly provide to the contrary;
provided, however, any such permitted transferee shall be required to (i)
execute a copy of this Agreement (or a separate consent thereto), and agree to
be bound by all of the terms and provisions hereof, (ii) assume all of its
transferor's obligations hereunder and sign any additional UCC-1 Financing
Statement, as required under this Agreement, and (iii) assume all of its
transferor's obligations under the DIHC Purchase Agreement. No such permitted
Transfer shall relieve the transferor from its obligations under the DIHC
Purchase Agreement, or from the transferor's obligations under Section 4.02(d)
hereof. Notwithstanding anything herein to the contrary, no transferee of a
partial interest of any Venturer shall have any right to participate in the
management of the Venture independents of the Venturer making such transfer
unless such participation is Approved by the Venturers.

      (f) The Transfer of all or any part of the interest of any Venturer which
is permitted hereunder shall not result in a dissolution of the Venture as a
general partnership under applicable law even though such Transfer may result in
the withdrawal of a Venturer as a general partner of the Venture and/or the
admission of a new general partner to the Venture.

      (g) Notwithstanding the prior provisions of this Section 6.02, a Venturer
may not Transfer all or any part of its interest in the Venture nor may a direct
or indirect owner of a Venturer Transfer all or any part of its interest in such
Venturer, if, solely as a result of such Transfer, all or any part of


                                      -25-
<PAGE>

the Venture's assets would thereafter become "tax-exempt use property" within
the meaning of section 168(h)(6) (or any successor provision) of the Code.

                                   ARTICLE VII

                    BUY-SELL UNDER THE MSA VENTURE AGREEMENT

      The parties recognize that the MSA Venturers have certain so-called
"buy-sell" rights and obligations under Section 5.02 of the MSA Venture
Agreement with respect to the sale of the MSA Venture Property or of an MSA
Venturer's interest in MSA, Subject to the rights of the Venturers with respect
to a sale or Transfer of their respective interests in the Venture under
Articles V and VI hereof, the Venturers agree that (a) the Venture shall not
make an Offer to the other MSA Venturer under Section 5.02 of the MSA Venture
Agreement unless such Offer and the 100% Price (as defined in the MSA Venture
Agreement) is Approved by the Venturers, and (b) if the other MSA Venturer makes
an Offer under Section 5.02 of the MSA Venture Agreement, then (i) the Venturers
shall decide whether they wish to purchase such interest of the other MSA
Venturer pursuant to the Venture's right to do so under such Section 5.02 of the
MSA Venture Agreement within thirty (30) days after they are notified of such
Offer by the other MSA Venturer, (ii) if all of the Venturers wish to purchase
such interest of the other MSA Venturer pursuant to the Venture's right to do so
under such Section 5.02 of the MSA Venture Agreement, the Venture shall purchase
such interest for the account of the Venturers pro rata according to their then
Percentage Interests or pursuant to such other formula as is Approved by the
Venturers, (iii) if less than all of the Venturers wish to purchase such
interest, then the party(ies) wishing to purchase such interest shall have the
right to cause the Venture to purchase such interest solely for the account of
such purchasing Venturer(s) (either in its own name or in the name of a nominee
or designee), but such party(ies) shall not have the right to also purchase the
interest of the other party(ies) in this Venture which does not wish to
participate in such purchase of the interest of the other MSA Venturer, and (iv)
all Venturers shall cooperate with one another to accomplish such result by
giving notice, executing documents and taking such other action as may be
reasonably required by the other Venturers in order to effectuate such result
promptly, timely and efficiently. Notwithstanding the foregoing, DIHC
acknowledges and agrees that it has waived its rights and/or privileges under
this Article VII pursuant to the DIHC Purchase Agreement unless and until the
DIHC Purchase Agreement is terminated for any reason without the Cornerstone
Purchase Option having been consummated, other than by default of Dutch
Institutional Holding Company, Inc. or DIHC thereunder. DIHC therefore
acknowledges and agrees that, until such time as the DIHC Purchase Agreement is
terminated without the Cornerstone Purchase Option having been consummated,
other than by default of Dutch Institutional Holding Company, Inc. or DIHC
thereunder, C-Stone may cause the Venture to make an Offer to or respond to an
Offer from the other MSA Venturer regarding the Venture's purchase of the
interest of the other MSA Venturer, without the consent or approval of DIHC.


                                      -26-
<PAGE>

                                  ARTICLE VIII

              RIGHT OF FIRST OFFER UNDER THE MSA VENTURE AGREEMENT

      The parties recognize that the MSA Venturers have certain so-called
"rights of first offer" under Section 6.04 of the MSA Venture Agreement with
respect to the sale of all or a portion of WALP's interest in AALP. Subject to
the rights of the Venturers with respect to a sale or Transfer of their
respective interests in the Venture under Articles V and VI hereof, the
Venturers agree that (a) the Venture shall not make a sale or Transfer of its
interest in MSA or cause MSA to make a sale or Transfer of its interest in AALP
unless same is Approved by the Venturers and (b) if the Venture at any time
obtains the right or option to acquire any interest of the other MSA Venturer in
MSA or any interest of WALP in AALP through any provision of the MSA Venture
Agreement or the AALP Partnership Agreement, then (i) the Venturers shall decide
whether they wish to cause the Venture to purchase such interest of the other
MSA Venturer pursuant to the MSA Venture Agreement or to cause MSA to purchase
such interest of WALP pursuant to the AALP Partnership Agreement within ten (10)
days after they are notified of the election giving rise to such right or option
by the other MSA Venturer or by WALP, as the case may be, (ii) if all of the
Venturers wish to purchase such interest, the Venture shall purchase, or shall
cause MSA to purchase, such interest for the account of the Venturers pro rata
according to their then Percentage Interests or pursuant to such other formula
as is Approved by the Venturers, (iii) if less than all of the Venturers wish to
purchase such interest, then the party(ies) wishing to purchase such interest
shall have the right to have the Venture purchase, or cause MSA to purchase,
such interest solely for the account of the purchasing Venturer(s) (either in
its own name or in the name of a nominee or designee), but such party(ies) shall
not have the right to also purchase the interest of the other party(ies) in this
Venture which does not wish to participate in such purchase of the interest of
the other MSA Venturer or the interest of WALP, and (iv) all Venturers shall
cooperate with one another to accomplish such result by giving notice, executing
documents and taking such other action as may be reasonably required by the
other Venturers in order to effectuate such result promptly, timely and
efficiently. Notwithstanding the foregoing, DIHC acknowledges and agrees that it
has waived its rights and/or privileges under clause (b) of this Article VIII
pursuant to the DIHC Purchase Agreement, unless and until the DIHC Purchase
Agreement is terminated for any reason without the Cornerstone Purchase Option
having been consummated, other than by default of Dutch Institutional Holding
Company, Inc. or DIHC thereunder. DIHC therefore acknowledges and agrees that,
until such time as the DIHC Purchase Agreement is terminated without the
Cornerstone Purchase Option having been consummated, other than by default of
Dutch Institutional Holding Company, Inc. or DIHC thereunder, C-Stone may
exercise any such right or option to cause the Venture to purchase any interest
of the other MSA Venturer pursuant to the MSA Venture Agreement, or to cause MSA
to purchase any interest of WALP pursuant to the AALP Partnership Agreement,
without the consent or approval of DIHC. Notwithstanding anything contained in
Articles VII or VIII of this Agreement, until the earlier of (i) January 30,
2000, or (ii) such time as PGGM shall have sold the stock of Dutch Institutional
Holding Company, Inc., or Dutch Institutional Holding Company, Inc. shall have
sold the stock of DIHC or a DIHC Transfer pursuant to Section 6.02(d) above,
C-Stone, in its capacity as the Managing Partner of the Venture, shall not,
except with the prior written consent of Dutch Institutional Holding Company,
Inc., (A) cause the


                                      -27-
<PAGE>

Venture to sell its interest in MSA, (B) cause the Venture to cause MSA to sell
its interest in AALP, or (C) cause the Venture to cause MSA to cause AALP to
sell the Land and the Improvements.

                                   ARTICLE IX

                                     GENERAL

Section 9.01. Notices

      (a) All notices, demands or requests provided for or permitted to be given
pursuant to this Agreement must be in writing.

      (b) All notices, demands and requests to be sent to a Venturer or any
permitted assignee of the interest of a Venturer hereunder pursuant hereto shall
be deemed to have been properly given or served either by (i) delivering the
same personally, (ii) by depositing the same in the United States mail,
addressed to such Venturer, postpaid and registered or certified with receipt
requested, or by sending by a recognized courier service, at the following
address or (iii) by sending a telecopy to such Venturer at the following
telecopy number:

                       If to DIHC:

                                     200 Galleria Parkway N.W.
                                     Suite 2000
                                     Atlanta, Georgia 30339
                                     Attention: Craig W. Johnston
                                     Telecopy No.: (770) 951-9349

                       With a copy to:

                                     Richards & O'Neil, LLP
                                     885 Third Avenue
                                     New York, New York 10022
                                     Attention: Robert M. Safron, Esq.
                                     Telecopy No.: (212) 750-9022

                       If to C-Stone:

                                     c/o Cornerstone Properties Inc.
                                     126 East 56th Street
                                     New York, New York 10022
                                     Attention: John S. Moody
                                     Telecopy No.: (212) 605-7199


                                      -28-
<PAGE>

                       With  a  copy  to:

                                     King & Spalding
                                     1185 Avenue of the Americas
                                     New York, New York 10036-4003
                                     Attention:  Eileen P. Brumback, Esq.
                                     Telecopy No.: (212) 556-2222

      (c) All notices, demands and requests shall be effective upon personal
delivery (including by courier, telecopy or telex) or upon receipt through the
United States mail. If the notice, demand or request is delivered by U.S. mail,
the time period in which a response to any such notice, demand or request must
be given shall commence to run from the date of receipt on the return receipt of
the notice, demand or request by the addressee thereof. Rejection or other
refusal to accept or the inability to deliver because of changed address (but
not because of changed telecopy or telex number) of which no notice was given
shall be deemed to be receipt of the notice, demand or request sent. In the
event that registered or certified mail is not being accepted for prompt
delivery, notices may then be served by personal service upon any officer,
director or partner of any Venturer or upon any individual who is a Venturer.

      (d) By giving to the other parties at least ten (10) days' written notice
thereof, the parties hereto and their respective successors and assigns shall
have the right from time to time and at any time during the term of this
Agreement to change their respective addresses and each shall have the right to
specify as its address any other address at which it has a place of business or
up to two (2) other addresses to which it wishes copies of any notice sent.

Section 9.02. Governing Laws

      This Agreement and the obligations of the Venturers hereunder shall be
interpreted, construed and enforced in accordance with the laws of the District
of Columbia.

Section 9.03. Exculpation/Indemnification

      (a) No Venturer (or any partner, director, officer or employee of any
Venturer) shall be personally liable or personally responsible to any other
Venturer or to the Venture beyond its interest in the assets of the Venture for
damages or other liabilities (other than for capital contributions required of
such Venturer under Section 4.02) caused by any act or omission performed or
omitted by it in respect of this Agreement or the Venture or the Property or
arising under any indemnity other than the indemnity set forth in Section
9.03(b) hereof and any other indemnities specifically agreed to by the Venturers
wherein the Venturers' liability to each other is not limited to their interest
in the Venture, unless such damage or liability results from its gross
negligence, fraud or willful misconduct.

      (b) Each Venturer shall defend, indemnify and hold the other Venturer and
its officers, directors, partners, shareholders, agents and employees harmless
from and against any third party


                                      -29-
<PAGE>

claims, demands, losses, damages or liabilities suffered or incurred by any of
them by reason of the fraud, gross negligence or wilful misconduct of such
Venturer, its officers, directors, partners, agents or employees.

      (c) Each Venturer hereby agrees to indemnify and hold harmless the other
Venturers from and against all liability, costs, damages and expenses from any
claims for brokerage commissions or other similar fees in connection with the
transactions covered by this Agreement insofar as such claims shall be based
upon arrangements or agreements made the indemnifying Venturer or on its behalf.

Section 9.04. Entire Agreement

      This Agreement contains the entire agreement between the parties hereto
relative to the formation of a Venture to own and operate the Property. No
variations, modifications or changes herein or hereof shall be binding upon any
party hereto unless set forth in a document duly executed by or on behalf of
such party.

Section 9.05. Waiver

      No consent or waiver, express or implied, by any Venturer to or of any
breach or default by the other in the performance by the other of its
obligations hereunder shall be deemed or construed to be a consent or waiver to
or of any other breach or default in the performance by such other party of the
same or any other obligations of such Venturer hereunder.

Section 9.06. Severability

      If any provision of this Agreement or the application thereof to any
person or circumstances shall be invalid or unenforceable to any extent, the
remainder of this Agreement and the application of such provisions to other
persons or circumstances shall not be affected thereby and shall be enforced to
the greatest extent permitted by law.

Section 9.07. Status Reports

      Recognizing that each party hereto may find it necessary from time to time
to establish to third parties such as accountants, banks, mortgagees or the
like, the then current status of performance hereunder, each party agrees, upon
the written request of any other, made from time to time, to wish promptly a
written statement (in recordable form, if requested) on the state of any matter
pertaining to this Agreement to the best of the knowledge and belief of the
party making such statement.

Section 9.08. Appraisals

      Any valuations of the Property or of the MSA Venture Property or of the
AALP Partnership


                                      -30-
<PAGE>

Property which the Venturers have agreed is to be determined by appraisals shall
be determined in accordance with the appraisal Procedure described in Exhibit I
to the MSA Venture Agreement. The appraised value of a Venturer's interest in
the Venture shall be the amount which such Venturer would have received under
this Agreement if the AALP Partnership Property had been sold for its fair
market value as determined in accordance with such appraisal procedure.

Section 9.09. Attorneys' Fees

      If the Venture or either Venturer obtains a judgment against another
Venturer by reason of its breach of this Agreement or failure to comply with the
provisions hereof, the defaulting Venturer shall pay the reasonable attorneys'
fees of the Venture or the prevailing Venturer.

Section 9.10. Terminology

      All personal pronouns used in this Agreement, whether used in the
masculine, feminine or neuter gender, shall include all other genders; the
singular shall include the plural and vice versa. Titles of Articles and
Sections are for convenience only, and neither limit nor amplify the provisions
of the Agreement itself, and all references herein to Articles, Sections or
subdivisions thereof shall refer to the corresponding Article, Section or
subdivision of this Agreement unless specific reference is made to such Article,
Sections or subdivisions of another document or instrument.

Section 9.11. Binding Agreement

      Subject to the restrictions on transfers and encumbrances set forth
herein, this Agreement shall inure to the benefit of and be binding upon the
undersigned Venturers and their respective successors and permitted assigns.
Whenever in this instrument a reference to any party or Venturer is made, such
reference shall be deemed to include a reference to the heirs, executors, legal
representatives, successors and permitted assigns of such party or Venturer.

Section 9.12. Additional Remedies

      Except as otherwise provided herein, the rights and remedies of the
Venturers hereunder shall not be mutually exclusive, i.e., the exercise of one
or more of the provisions hereof shall not preclude the exercise of any other
provisions hereof.

Section 9.13. Meetings

      Meetings of the Venturers may be called by any Venturer for any matter on
which the Venturers may act pursuant to the terms of this Agreement, upon the
giving of not less than five (5) days' advance written notice. The Venturers
will endeavor to conduct such meetings by telephone.

Section 9.14. Partition


                                      -31-
<PAGE>

      Each Venturer hereby waives any right of partition under the laws of the
District of Columbia.

Section 9.15. Conflict with the MSA Venture Agreement and AALP Partnership
Agreement

      In the event of any conflicts or inconsistencies between the provisions of
this Agreement or the rights and obligations of the Venturers hereunder and the
provisions of the MSA Venture Agreement and/or the AALP Partnership Agreement
and the rights and obligations of the MSA Venturers or AALP Partners, as the
case may be, thereunder, the provisions of the AALP Partnership Agreement shall
govern and prevail over the MSA Venture Agreement and this Agreement, and the
Provisions of the MSA Venture Agreement shall govern and prevail over this
Agreement.

Section 9.l6. Conflicts with the DIHC Purchase Agreement

      In the event of any conflicts or inconsistencies between the provisions of
this Agreement or the rights and obligations of the Venturers hereunder and the
provisions of the DIHC Purchase Agreement and the rights and obligations of the
Venturers thereunder, the provisions of this Agreement shall govern and prevail
over the DIHC Purchase Agreement.

                            [SIGNATURE PAGES FOLLOW]


                                      -32-
<PAGE>

                  IN WITNESS WHEREOF, this Agreement is executed effective as of
the date first set forth above.

                          "C-STONE"

                          CORNERSTONE MARKET SQUARE LLC, a Delaware
                          limited liability company

                          By:  CORNERSTONE PROPERTIES LIMITED
                               PARTNERSHIP, a Delaware limited partnership, its
                               sole member

                               By:  CORNERSTONE PROPERTIES INC., a
                                    Nevada corporation, its sole general partner

                                    By:____________________________________
                                         Name:_____________________________
                                         Title:____________________________


                                       S-1
<PAGE>

                                    "DIHC"

                                    DIHC MARKET SQUARE, INC., a Georgia
                                    corporation, a General Partner

                                    By:____________________________________
                                         Name:_____________________________
                                         Title:____________________________

                                       S-1
<PAGE>

                                    EXHIBIT A

                            Legal Description of Land

                                       A-1