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                                                                  Exhibit 10.117


                     REDEMPTION AND ACQUISITION AGREEMENT

            THIS REDEMPTION AND ACQUISITION AGREEMENT (this "Agreement") made as
of October 27, 1997 by and among MARKET SQUARE DEVELOPMENT INVESTORS (the
"Company"), a District of Columbia general partnership having an office at 200
Galleria Parkway N.W., Suite 2000, Atlanta, Georgia 30339, DUTCH INSTITUTIONAL
HOLDING COMPANY, INC. ("DIHC"), a Delaware corporation, having an office at 200
Galleria Parkway N.W., Suite 2000, Atlanta, Georgia 30339, and DIHC MARKET
SQUARE, INC. ("DIHC-MS"), a Georgia corporation, having an office at 200
Galleria Parkway, N.W., Suite 2000, Atlanta, Georgia 30339, and CORNERSTONE
PROPERTIES INC. ("C-Stone"), a Nevada corporation, having an office at 126 East
56th Street, New York, New York 10022.

                             W I T N E S S E T H:

            WHEREAS, as of the date of this Agreement, M.I. West Pennsylvania
Limited Partnership ("M.I. West") and DIHC-MS are the sole partners in the
Company, which in turn is one of the venturers in Market Square Associates
("MSA"), a District of Columbia general partnership, which in turn is one of the
venturers in Avenue Associates Limited Partnership ("AALP"), a District of
Columbia limited partnership which owns the land and improvements located at 701
and 801 Pennsylvania Avenue located in the District of Columbia (the
"Property");

            WHEREAS, DIHC is the parent corporation of DIHC-MS and DIHC is a
wholly-owned subsidiary of Stichting Pensioenfonds voor de Gezondheid
Geestelijke en Maatschappelijke Belangen ("PGGM");

            WHEREAS, the Company, DIHC and M.I. West entered into that certain
Redemption Agreement dated as of August 15, 1997 (the "M.I. Redemption
Agreement"), pursuant to which, at or prior to the Redemption Date (as
hereinafter defined), a new partner is to be admitted to the Company (the "New
Partner"), and the Company is to redeem from M.I. West all of M.I. West's right,
title and interest in and to the Company (the "M.I. Redemption");

            WHEREAS, DIHC and C-Stone entered into that certain Stock Purchase
Agreement dated as of August 18, 1997 between DIHC, as Seller, and C-Stone, as
Purchaser (the "Stock Purchase Agreement"), and PGGM and C-Stone entered into
that certain Loan Purchase Agreement dated as of August 18, 1997 between PGGM,
as Seller, and C-Stone, as Purchaser (the "Loan Purchase Agreement");


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            WHEREAS, pursuant to the Loan Purchase Agreement, immediately prior
to the execution and delivery of this Agreement, C-Stone acquired all of the
holder's right, title and interest in and to that certain loan originally from
DIHC Finance Corporation to AALP in the original principal amount of
$188,491,750, which loan has been assigned to PGGM and is secured by (among
other things) that certain Deed of Trust and Security Agreement dated as of July
15, 1987 recorded as Instrument No. 38127, among the Land Records of the
District of Columbia, as amended (the "AALP Mortgage"); and pursuant to the
Stock Purchase Agreement, immediately prior to the execution and delivery of
this Agreement, C-Stone acquired all of the holder's beneficial right, title and
interest in and to that certain loan from DIHC Finance Corporation to the
Company in the original principal amount of up to $41,900,000, which loan is
evidenced by that certain Promissory Note and Loan Agreement from the Company to
DIHC Finance Corporation dated as of August 15, 1997 (the "MSDI Loan");

            WHEREAS, the Company desires to admit C-Stone, and C-Stone desires
to be admitted, as the New Partner in accordance with the M.I. Redemption
Agreement;

            WHEREAS, the Company further desires to redeem from DIHC-MS, and
DIHC-MS desires to transfer to the Company, all of the right, title and interest
of DIHC-MS in and to the Company, other than the Retained Interest (as
hereinafter defined), subject to the terms of this Agreement; and

            WHEREAS, C-Stone further desires to purchase from DIHC-MS, and
DIHC-MS desires to sell to C-Stone the Retained Interest of DIHC-MS in the
Company, subject to the terms of this Agreement.

            NOW, THEREFORE, in consideration of the mutual agreements and
covenants contained herein, and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties agree as
follows:

      II. Definitions. For purposes of this Agreement, unless the context
otherwise requires the following terms shall have the following meanings:

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

            D. "Interest" means all right, title and interest of DIHC-MS in and
to the Company, other than the Retained Interest, subject and pursuant to the
Venture Agreement.

            F. "Person" means any individual, partnership, firm, corporation,
association, trust, unincorporated organization or other entity, as well as any
syndicate or


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group that would be deemed to be a person under Section 13(d)(3) of the
Securities Exchange Act of 1934, as amended.

            H. "Redemption Date" means the date upon which the M.I. Redemption
is closed, and upon such date and immediately following the M.I. Redemption, the
Company shall redeem the Interest from DIHC-MS in accordance with the terms of
this Agreement.

            J. "Redemption Instrument" means the instrument of redemption and
assumption pursuant to which the Company redeems the Interest of DIHC-MS in the
Company, in the form of Exhibit "A" annexed hereto.

            L. "Restated Venture Agreement" means the Second Amended and
Restated Joint Venture Agreement of the Company to be mutually agreed upon and
entered into by and between C-Stone and DIHC-MS on the Redemption Date in
accordance with Section 5 hereof.

            N. "Retained Interest" means a Percentage Interest (as defined in
the Venture Agreement) equal to one percent (1%) of the total interests in the
Company, including one percent (1%) of all distributions to the venturers of the
Company and one percent (1%) of the income of the Company, which shall be
retained and owned by DIHC-MS until the Sale Date.

            P. "Sale Date" means a date upon which the closing of C-Stone's
purchase of the Retained Interest shall take place, as designated in a notice by
C-Stone to DIHC-MS at least sixty (60) days prior to such date, which shall be a
date at any time within two (2) years after the Redemption Date; provided that
in the event the Closing Date shall not have occurred within two (2) years after
the Redemption Date for any reason whatsoever other than the willful misconduct
or gross negligence of DIHC-MS, its employees, agents or representatives (the
"Outside Date"), DIHC-MS shall have the right to (a) terminate the remaining
terms of this Agreement applicable to the transfer of the Retained Interest,
upon notice given not later than three (3) business days after the Outside Date
unless, as of the Outside Date, the closing of the transaction contemplated
hereby is prevented or barred by reason of force majeure, court order or
governmental action, or (b) enforce this Agreement by an action for specific
performance and/or damages.

            R. "Sale Instrument" means the instrument of sale and assumption
pursuant to which C-Stone shall purchase the Retained Interest of DIHC-MS in the
Company, in the form of Exhibit "B" annexed hereto.

            T. "Venture Agreement" means the Amended and Restated Joint Venture
Agreement of the Company dated January 27, 1989 between DIHC-MS and M.I. West.


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            V. "Herein", "hereof" or "hereunder" or any similar term used in
this Agreement refers to this entire Agreement rather than only to the
particular provision in which the term is used.

            X. References to Articles, Sections or other provisions are
references to articles, sections or other provisions hereof.

            Z. The singular includes the plural and vice versa, and a reference
to any one gender, masculine, feminine or neuter, includes the other two.

            BB. "Best knowledge of DIHC" or "best knowledge of DIHC-MS" means
the best knowledge of Robert T. Sorrentino, Michael F. Perkins and Craig W.
Johnston.

            DD. Terms which are capitalized in this Agreement but are not
separately defined in this Agreement shall have the same meanings in this
Agreement as in the Stock Purchase Agreement.

      IV. Admission of New Partner. On or immediately prior to the Redemption
Date and subject to Section 11.5 below, C-Stone will make a capital contribution
(the "Contribution") to the Company in an amount equal to Redemption Price (as
defined in the M.I. Redemption Agreement), plus any required interest thereon
pursuant to the M.I. Redemption Agreement, to be paid by the Company to
consummate the M.I. Redemption. The Contribution shall be paid to the Company by
electronic transfer of federal funds pursuant to wire instructions to be
provided to C-Stone by the Company. Upon payment of the Contribution, DIHC-MS
shall admit C-Stone as the New Partner to the Company subject to the terms of
the M.I. Redemption Agreement.

      VI. M.I. Redemption. Upon admission of C-Stone as the New Partner, DIHC
shall cause the M.I. Redemption to be closed in accordance with the terms of the
M.I. Redemption Agreement.

      VIII. Loan to Company. Immediately following the M.I. Redemption, C-Stone
shall loan an amount equal to the DIHC Redemption Price determined in accordance
with Section 6 below to the Company either by advancing additional funds under
the MSDI Loan, if the same can be advanced thereunder without exceeding the
maximum principal balance thereof, or making a new recourse loan to the Company
in such amount, such a new loan to be evidenced by a Promissory Note and Loan
Agreement to be executed by the Company in favor of C-Stone in the form of
Exhibit "C" annexed hereto. The proceeds of any such loan shall be paid to the
Company by electronic transfer of federal funds pursuant to wire instructions to
be provided to C-Stone by the Company.

      X. DIHC Redemption. On the Redemption Date and immediately following the
M.I. Redemption and the funding of the loan referred to in Section 4 above,
DIHC-MS shall


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transfer all of its right, title and interest in and to the Interest to the
Company, and the Company shall redeem the Interest from DIHC-MS for the DIHC
Redemption Price (as defined in Section 6 below) and upon the other terms,
covenants and conditions contained herein (the "DIHC Redemption"). The closing
of the DIHC Redemption shall take place at the offices of Richards & O'Neil,
LLP, 885 Third Avenue, New York, New York or as otherwise agreed to by the
parties. Notwithstanding the foregoing, the closing of the DIHC Redemption may
be effected by mail pursuant to an escrow agreement reasonably satisfactory to
the parties hereto. Immediately following the completion of the M.I. Redemption
and the DIHC Redemption, C-Stone and DIHC-MS shall execute and deliver the
Restated Venture Agreement, pursuant to which C-Stone shall replace DIHC-MS as
the Managing Venturer (as defined in the Venture Agreement) of the Company.

      XII. DIHC Redemption Price. The redemption price (the "DIHC Redemption
Price") to be paid to DIHC-MS for the Interest shall be an amount equal to
$2,867,000.00, plus an amount equal to $434.00 times the number of days between
the date of this Agreement and the Redemption Date, and such additional
adjustments (the "Post-Redemption Adjustments") to be made between the parties
within ninety (90) days after the Redemption Date on account of working capital
prorations under the Venture Agreement, which Post-Redemption Adjustments the
parties agree will be determined by Coopers & Lybrand L.L.P. The DIHC Redemption
Price shall be paid to DIHC-MS or its designee on the Redemption Date by
electronic transfer of federal funds pursuant to wire instructions to be
provided to the Company by DIHC-MS. In the event that the Post- Redemption
Adjustments result in (a) a credit to DIHC-MS, the Company agrees to promptly
wire the amount of such credit to DIHC-MS or its designee in accordance with the
wire instructions to be provided to the Company by DIHC-MS, or (b) a credit to
the Company, DIHC-MS agrees to promptly wire the amount of such credit to the
Company or its designee in accordance with the wire instructions to be provided
to DIHC-MS by the Company. The provisions of this Section 6 shall survive the
execution and delivery of this Agreement and the closing of the transactions
contemplated hereunder.

      XIV. Purchase and Sale of Retained Interest. On the Sale Date, C-Stone
shall purchase and acquire all of the right, title and interest of DIHC-MS in
and to the Retained Interest in the Company, and DIHC-MS shall sell and convey
the Retained Interest to C-Stone for the Purchase Price (hereinafter defined)
and upon the other terms, covenants and conditions contained herein (the
"Closing"). The Closing shall take place on the Sale Date at in the offices of
King & Spalding, 1185 Avenue of the Americas, New York, New York, or as
otherwise agreed to by the parties. Notwithstanding the foregoing, the Closing
may be effected by mail pursuant to an escrow agreement reasonably satisfactory
to the parties hereto.

      XVI. Purchase Price. The Purchase Price (the "Purchase Price") to be paid
by C-Stone for the Retained Interest shall be an amount equal to $50,000.00. The
Purchase Price shall be paid to DIHC-MS or its designee on the Sale Date by
payment of $18,000.00 in cash by electronic transfer of federal funds pursuant
to wire instructions to be provided to C-Stone


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<PAGE>

by DIHC-MS, and by transfer to DIHC of 2,000 validly issued, fully paid and
nonassessable shares of common stock of C-Stone with no par value (adjusted as
necessary to fully reflect the effect of any stock split, reverse stock split,
or stock dividend with respect to such common shares occurring after the date of
the Stock Purchase Agreement and prior to the date of Closing) having an agreed
value of $16.00 per share and not subject to adjustment notwithstanding any
changes in the stock price between the date of the Stock and Loan Purchase
Agreements and the Closing ("C-Stone Common Shares"), which shares shall be
subject to that certain Registration Rights and Voting Agreement of even date
herewith entered into between DIHC and Cornerstone pursuant to the Stock
Purchase Agreement.

      XVIII.Representations, Warranties and Covenants of DIHC and DIHC-MS. DIHC
and DIHC-MS each hereby make the following representations, warranties and
covenants as of the date hereof (on the condition that all such representations,
covenants and warranties relate to the time period from and after the initial
acquisition of the Interest by DIHC-MS until the Redemption Date, and, with
respect to the Retained Interest, until the Sale Date):

            B. DIHC-MS is a corporation duly organized and in good standing
under the laws of the State of Georgia, and, to the extent necessary, is in good
standing and qualified in the District of Columbia.

            D. DIHC-MS has full corporate power and authority to execute and
deliver this Agreement, to transfer the Interest to the Company and the Retained
Interest to C-Stone and to comply with each of the provisions hereof. The
execution and delivery of this Agreement has been duly authorized and approved
by all necessary corporate action and no further consents or approvals are
required from any governmental authority or Person for DIHC-MS to enter into and
perform its obligations under this Agreement; provided, however, DIHC and
DIHC-MS make no representation as to whether any consent or approval from any of
the other venturers in MSA or AALP is required for DIHC-MS to enter into and
perform its obligations under this Agreement.

            F. To the best knowledge of DIHC and DIHC-MS, except as otherwise
specifically disclosed herein, DIHC-MS is not currently in default, and the
execution, delivery and performance of its obligations under this Agreement will
not constitute a default by DIHC-MS, with respect to any of its obligations
under the Venture Agreement; provided, however, DIHC and DIHC-MS make no
representation as to whether any consent or approval from any of the other
venturers in MSA or AALP is required for DIHC-MS to enter into and perform its
obligations under this Agreement.

            H. DIHC-MS owns the Interest and the Retained Interest free and
clear of all mortgages, pledges, liens, charges, claims, title retention or
other security arrangements or obligations to other Persons, options and
encumbrances of every kind, and DIHC-MS has not heretofore sold, assigned,
pledged, encumbered or in any way transferred or granted any rights


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with respect to the Interest or the Retained Interest other than the AALP
Mortgage and the MSDI Loan; provided, however, DIHC and DIHC-MS make no
representation as to whether any consent or approval from any of the other
venturers in MSA or AALP is required for DIHC-MS to enter into and perform its
obligations under this Agreement.

            J. Except as provided in this Section 9.5, DIHC and DIHC-MS will
defend title to the Interest from and against all lawful claims and demands
whatsoever, at law or in equity, of all Persons; provided, however, DIHC and
DIHC-MS make no representation as to whether any consent or approval from any of
the other venturers in MSA or AALP is required for DIHC-MS to enter into and
perform its obligations under this Agreement, and, provided further, however,
DIHC and DIHC-MS shall have no obligation to defend the transfer of title to the
Interest to the Company or the transfer of title to the Retained Interest to
C-Stone from any claim or demand whatsoever, at law or in equity, under the
Underlying Venture Documents (as hereinafter defined) by any venturer in MSA or
AALP (any such claim or demand by any venturer in MSA or AALP under the
Underlying Venture Documents is hereinafter referred to as a "Venturer Claim").
Notwithstanding the foregoing, in the event of any Venturer Claim, DIHC and
DIHC-MS agree, at the sole cost and expense of C-Stone, to fully cooperate with
the Company, C-Stone and their Affiliates in the defense of any such Venturer
Claim, including, but not limited to, making available all files relating to the
interest of DIHC-MS in the Venture and agreeing to testify in any action or
proceeding relating to any Venturer Claim.

            L. DIHC-MS has timely filed or obtained extensions for all federal
and foreign income tax returns and state, county, and local income, franchise,
property, sales, use, unemployment, and other tax returns in each state and
jurisdiction where such returns are required to be filed on or prior to the date
hereof, the Redemption Date or the Sale Date, as applicable, taking into account
any extensions of the filing deadlines which have been validly granted to
DIHC-MS, and such returns are and will be true and correct in all material
respects. DIHC-MS has paid in full or will pay in full before delinquency all
federal, foreign, state, county, and local income, franchise, property, sales,
use, and all other taxes and assessments (including penalties and interest in
respect thereof, if any) that have become or will become due with respect to any
period ended on or prior to the date hereof, the Redemption Date or the Sale
Date, as applicable, whether shown as due on such returns or not, or is
contesting in good faith or will contest in good faith such taxes and
assessments, in which event DIHC-MS has disclosed or will disclose the details
of such contests in writing to the Company and C-Stone.

            N. To the best knowledge of DIHC-MS, there are no pending, and
DIHC-MS has not received any notice of any, federal, foreign, state, or local
tax disputes in which DIHC-MS is alleged to be liable for additional taxes.

            P. To the best knowledge of DIHC and DIHC-MS, no claim or
investigation is pending or threatened by any state, local, or other
jurisdiction alleging that


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either DIHC or DIHC-MS has a duty to file tax returns and pay taxes or is
otherwise subject to the taxing authority of any jurisdiction in which either
DIHC or DIHC-MS has not filed tax returns, nor has DIHC nor DIHC-MS received any
notice or questionnaire from any such jurisdiction which suggests or asserts
that either DIHC or DIHC-MS may have a duty to file such returns and pay such
taxes, or otherwise is subject to the taxing authority of such jurisdiction.

            R. Neither the execution and delivery of this Agreement nor the
consummation of the transactions contemplated herein in the manner herein
provided will violate any agreement or instrument to which DIHC or DIHC-MS is a
party or by which DIHC or DIHC-MS is bound; provided, however, DIHC and DIHC-MS
make no representation as to whether any consent or approval from any of the
other venturers in the Company, MSA or AALP is required for DIHC-MS to enter
into and perform its obligations under this Agreement.

            T. To the best knowledge of DIHC and DIHC-MS, there is no action,
suit or proceeding pending or threatened against or affecting the Interest or
the Retained Interest in any court or before or by any federal, state, county or
municipal department, commission, board, bureau or agency or other governmental
instrumentality, except for that certain lawsuit by Western Avenue Associates
Limited Partnership filed in United States District Court for the District of
Columbia under case number 1:97CV02452 (the "Western Litigation").

            V. DIHC-MS is not a "foreign person" as defined in Section 1445 of
the Internal Revenue Code (as amended, the "Code").

            X. To the best knowledge of DIHC and DIHC-MS, there are no written
documents, agreements, correspondence or other instruments initiated or prepared
by DIHC or DIHC-MS relating to or dealing with transferability of an interest in
the Company or any venturer therein except for the agreements set forth in
Schedule A annexed hereto (collectively, the "Underlying Venture Agreements").

            Z. Neither DIHC nor DIHC-MS is insolvent or will be rendered
insolvent by the consummation of the transactions contemplated hereunder.

            BB. The Company is a general partnership organized and in good
standing under the laws of the District of Columbia and DIHC-MS and M.I. West
are its sole general partners as of the date hereof, and upon completion of the
M.I. Redemption contemplated herein and the admission of C-Stone as provided in
Section 2 above, the sole general partners of the Company shall be DIHC-MS and
C-Stone.

            DD. The Company has full partnership power and authority to execute
and deliver this Agreement, to accept the transfer of the Interest from DIHC-MS,
and to comply with each of the provisions hereof. The execution and delivery of
this Agreement has been


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duly authorized and approved by the Company by DIHC-MS as its Managing Venturer
and no further consent or approvals are required from any governmental authority
or Person for the Company to enter into and perform its obligations under this
Agreement; provided, however, DIHC and DIHC-MS make no representation as to
whether any consent or approval from any of the other venturers in the Company,
MSA or AALP is required to enter into and perform its obligations under this
Agreement.

            FF. Neither the execution and delivery of this Agreement nor the
consummation of the transactions contemplated herein in the manner herein
provided will violate any agreement or instrument to which the Company is a
party or by which the Company is bound, including, without limitation, the
Underlying Venture Agreements; provided, however, DIHC and DIHC-MS make no
representation as to whether any consent or approval from any of the other
venturers in the Company, MSA or AALP is required to enter into and perform its
obligations under this Agreement.

            HH. The Company is not insolvent and will not be rendered insolvent
by the consummation of the transactions contemplated hereunder.

      XX. Representations, Warranties and Covenants of C-Stone. C-Stone makes
the following representations, warranties and covenants:

            B. C-Stone is a Nevada corporation duly organized and in good
standing under the laws of Nevada, and, to the extent necessary, in the District
of Columbia.

            D. C-Stone has full power and authority to execute and deliver this
Agreement and to comply with each of the provisions hereof. The execution and
delivery of this Agreement has been duly authorized and approved by C-Stone and
no further consents or approvals are required from any governmental authority or
Person for C-Stone to enter into and perform its obligations under this
Agreement.

            F. Neither the execution and delivery of this Agreement nor the
consummation of the transactions contemplated herein in the manner herein
provided will violate any agreement or instrument to which the C-Stone is a
party or by which C-Stone is bound.

            H. C-Stone is not insolvent and will not be rendered insolvent by
the consummation of the transactions contemplated hereunder.

      XXII. Additional Agreements.


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            B. Conduct of Business of the Company Prior to Redemption: Competing
Transactions. DIHC and DIHC-MS covenant and agree that, between the date hereof
and the Redemption Date:

                  2. DIHC and DIHC-MS (a) shall cause the Company, MSA, AALP and
      the Property to be operated in the ordinary and usual course of business
      and consistent with the Company's prior practice; (b) shall not, directly
      or indirectly through any officer, trust manager, employee, agent,
      investment banker, financial advisor, attorney, accountant, broker or
      other representative, initiate, solicit or effect the sale or listing for
      sale of any direct or indirect interest in the Company, MSA, AALP or the
      Property without the prior written consent of C-Stone, which shall not be
      unreasonably withheld; (c) shall use their commercially reasonable efforts
      to preserve the good will and advantageous relationships of the Company
      with tenants, customers, suppliers, independent contractors and other
      Persons material to the operation of the Property; (d) shall perform their
      material obligations under any contracts or agreements affecting the
      Property; and (e) shall not wilfully or knowingly take or permit any
      action or omission which would cause any of their representations or
      warranties contained herein to become inaccurate in any material respect
      or any of the covenants made by them to be breached in any material
      respects;

                  4. DIHC and DIHC-MS will not cause or permit any default to
      occur by the Company, MSA or AALP under any indebtedness of the Company,
      MSA or AALP, or any indebtedness secured by the Property, or cause or
      permit any increase in the outstanding principal balance thereof (other
      than the MSDI Loan), or cause or permit the Company, MSA or AALP to incur
      any additional indebtedness or make any loans, advances or capital
      contributions in or to any other Person, without the prior written consent
      of C-Stone, which shall not be unreasonably withheld.

                  6. DIHC and DIHC-MS shall cause the Company, MSA and AALP to
      continue to maintain all of its insurance policies with respect to the
      Property in full force and effect.

                  8. DIHC-MS shall not effect any change in its capital
      structure or initiate, solicit or effect any merger, consolidation, share
      exchange, business combination, or similar transaction with any Person or
      sell, or grant any option or right in respect of, any shares of its common
      stock, any of its other voting securities or any of its securities
      convertible into, or any rights, warrants or options to acquire, any such
      shares, voting securities or convertible securities, except that, with the
      prior written consent of C-Stone, which consent shall not be unreasonably
      withheld, DIHC-MS may undertake internal restructuring transactions.

                  10. DIHC-MS shall not, and shall not permit the Company, MSA
      or AALP to, amend the articles or certificate of incorporation, charter,
      bylaws,


                                      10
<PAGE>

      partnership agreement, or other comparable charter or organizational
      documents of the Company, MSA or AALP, except to the extent necessary to
      carry out internal restructuring transactions referred to in Subsection
      11.1.4 above that are consented to by C-Stone in accordance herewith.

                  12. DIHC and DIHC-MS will not cause or permit any default to
      occur by the Company, MSA or AALP under any of the contracts or agreements
      affecting the Property, and shall cause the Company, MSA and AALP to
      perform their obligations under such contracts and agreements, and shall
      not permit the Company, MSA or AALP to modify, amend or terminate any such
      contracts or agreements without the prior written consent of C-Stone,
      which shall not be unreasonably withheld.

                  14. Without the prior written consent of C-Stone (which shall
      not be unreasonably withheld), DIHC and DIHC-MS shall not permit the
      Company, MSA or AALP to (i) enter into any new contract or agreement
      regarding the Company, MSA, AALP or the Property or grant concessions
      regarding any existing contract or agreement affecting the Company, MSA,
      AALP or the Property, or (ii) enter into any lease for space in the
      Property, or modify, amend, renew or terminate (except in connection with
      a tenant default) any existing lease for space in the Property.

                  16. Notwithstanding the provisions of this Section 11.1, the
      parties acknowledge and agree that, with respect to the Company, MSA and
      AALP, neither DIHC nor DIHC-MS own (directly or indirectly) all of the
      equity interest in such entities and therefore do not unilaterally control
      all actions and decisions of such entities, except that as of the date
      hereof and up until the Redemption Date DIHC-MS is and shall remain the
      Managing Venturer of the Company pursuant to the Venture Agreement.
      Accordingly, the parties agree that, with respect to the Company, MSA and
      AALP, DIHC and DIHC-MS shall be deemed to have complied with the foregoing
      covenants in the event that DIHC or DIHC- MS performs such covenants
      consistent with their rights under, and subject to any limitations on
      their authority or fiduciary duties under, the joint venture or
      partnership agreements for such entities or applicable law.

            D. Commercially Reasonable Efforts; Notification. Subject to the
terms and conditions of this Agreement, the parties shall (a) use all
commercially reasonable efforts to cooperate with one another in (i) determining
which filings are required to be made prior to the Redemption Date or the Sale
Date with, and which consents, approvals, permits or authorizations are required
to be obtained prior to the Redemption Date or the Sale Date from, governmental
or regulatory authorities of the United States, the several states and foreign
jurisdictions and any third parties in connection with the transactions
contemplated by this Agreement, and (ii) timely making all such filings and
timely seeking all such consents, approvals, permits and authorizations; (b) use
all commercially reasonable efforts to obtain in writing any consents required
from third parties to effectuate the transactions contemplated by


                                      11
<PAGE>

this Agreement, such consents to be in form reasonably satisfactory to the
parties hereto; and (c) use all commercially reasonable efforts to take, or
cause to be taken, all other action and do or cause to be done, all other things
necessary, proper or appropriate to consummate and make effective the
transactions contemplated by this Agreement. Prior to the Redemption Date and
the Sale Date, as applicable, the parties hereto shall deliver to the others
information supplementing or amending the representations and warranties set
forth in Articles 9 and 10 of this Agreement to set forth the information
relating to any event or circumstance arising after the date of this Agreement,
in order to make such representations and warranties complete and accurate as of
the date of such supplement or amendment.

            F. Transfer and Gains Taxes. The parties hereto shall cooperate in
the preparation, execution and filing of all returns, questionnaires,
applications or other documents regarding any transfer or gain, sales, use,
recording, intangible, value added, stock transfer and stamp taxes, any
transfer, recording, registration and other fees and any similar taxes which
become payable in connection with the transactions contemplated hereby,
excluding state and federal income taxes (together with any related interest,
penalties or additions to such taxes, "Transfer and Gains Taxes"). Any Transfer
and Gains Taxes due and payable in connection with the transactions contemplated
by this Agreement shall be shared equally between DIHC-MS and C-Stone.

            H. Access to Information.

                  2. From the date hereof until the Redemption Date, upon
      reasonable notice, each party and their respective officers, directors,
      employees, agents, accountants and counsel shall: (i) afford the officers,
      employees and authorized agents, accountants, counsel, financing sources
      and representatives of the other party reasonable access, during normal
      business hours, to the properties, offices, other facilities, books and
      records of such party and to those officers, directors, employees, agents,
      accountants and counsel of such party who have any knowledge relating to
      such party or its properties, and (ii) furnish to the officers, employees
      and authorized agents, accountants, counsel, financing sources and
      representatives of the other party such additional financial and operating
      data and other information regarding it and its properties as the other
      party may from time to time reasonably request.

                  4. In order to facilitate the resolution of any claims made
      against or incurred by DIHC or DIHC-MS prior to the Redemption Date, for a
      period of seven (7) years after the Redemption Date, C-Stone or the
      Company shall (i) retain the books and records of DIHC and DIHC-MS which
      are transferred to C-Stone or the Company pursuant to this Agreement, if
      any, relating to periods prior to the Redemption Date in a manner
      reasonably consistent with the prior practices of DIHC and DIHC-MS, and
      (ii) upon reasonable notice, afford the officers, employees and authorized
      agents and representatives of DIHC and DIHC-MS reasonable access
      (including the right to make,


                                      12
<PAGE>

      at their expense, photocopies), during normal business hours, to such
      books and records.

                  6. In order to facilitate the resolution of any claims made by
      or against or incurred by C-Stone or the Company after the Redemption Date
      or for any other reasonable purpose, for a period of seven (7) years
      following the Redemption Date, DIHC and DIHC-MS, as applicable, shall (i)
      retain all books and records of DIHC and DIHC-MS which are not transferred
      to C-Stone or the Company pursuant to this Agreement and which relate to
      the Company, MSA, AALP or the Property for the period prior to the
      Redemption Date (including, without limitation, employee files relating to
      the employees of DIHC and DIHC-MS which do not become employees of
      C-Stone), and (ii) upon reasonable notice, afford the officers, employees
      and authorized agents and representatives of C-Stone and the Company
      reasonable access (including the right to make photocopies at their
      expense), during normal business hours, to such books and records.

                  8. Notwithstanding the provisions of this Section 11.4, the
      parties acknowledge and agree that, with respect to the Company, MSA and
      AALP, neither DIHC nor DIHC-MS own (directly or indirectly) all of the
      equity interest in such entities and therefore do not unilaterally control
      all actions and decisions of such entities, except that as of the date
      hereof and up until the Redemption Date DIHC-MS is and shall remain the
      Managing Venturer of the Company pursuant to the Venture Agreement.
      Accordingly, the parties agree that, with respect to the Company, MSA and
      AALP, DIHC and DIHC-MS shall be deemed to have complied with the foregoing
      covenants regarding access to and retention of records in the event that
      DIHC or DIHC-MS performs such covenants consistent with their rights
      under, and subject to any limitations on their authority or fiduciary
      duties under, the joint venture or partnership agreements for such
      entities or applicable law.

            J. Performance under MI Redemption Agreement. Upon the making by
C-Stone of the Contribution as specified in Section 2 above, DIHC and DIHC-MS
shall cause the Company to redeem the interest of M.I. West in the Company
pursuant to the M.I. Redemption Agreement, the Percentage Interest of C-Stone in
the Company shall be increased to equal the former Percentage Interest of M.I.
West. C-Stone covenants to make the Contribution as and when requested by DIHC
and DIHC-MS upon no less than ten (10) days' prior written notice and within the
permissible time periods for a "Closing" under the M.I. Redemption Agreement,
and DIHC and DIHC-MS covenant and agree that, upon the making by C-Stone of the
Contribution, DIHC shall perform its obligations under the M.I. Redemption
Agreement as provided therein in a timely manner, and shall cause the redemption
of the interest of M.I. West in the Company and the resultant increase in the
Percentage Interest of C-Stone in the Company. C-Stone agrees to indemnify DIHC
and its Affiliates as of the date hereof for all obligations and liabilities of
DIHC under Section 10 of the M.I. Redemption Agreement in respect of capital
calls by the Company, and agrees to fund all


                                     13
<PAGE>

capital calls required to be made on behalf of M.I. West pursuant to Section 10
of the M.I. Redemption Agreement. Any such capital calls funded by C-Stone on
behalf of M.I. West and any other payments made by C-Stone pursuant to the
indemnity in this Section 11.5 shall be treated as a loan to the Company, and
either treated as an advance under the MSDI Loan, if the same can be advanced
thereunder without exceeding the maximum principal balance thereof, or as a new
recourse loan to the Company to be evidenced by a Promissory Note and Loan
Agreement from the Company in favor of C-Stone substantially in the form of
Exhibit "C" annexed hereto. In the event the Closing under the M.I. Redemption
Agreement is not closed solely due to a wilful default by DIHC, DIHC shall
reimburse C-Stone for any such loan made by C-Stone, and this Agreement shall
thereupon be terminated and of no further force or effect.

            L. Western Litigation. The parties acknowledge that Western Avenue
Associates Limited Partnership, one of the partners in AALP, has filed the
Western Litigation against, among others, the Company, DIHC and DIHC-MS. The
Company, DIHC and DIHC-MS hereby covenant and agree, for the period between the
date hereof and the completion of the DIHC Redemption, to keep C-Stone fully
informed of the progress of all matters occurring in connection with the Western
Litigation.

      XXIV. Conditions to Obligations.

            B. Conditions to Obligations of DIHC and DIHC-MS. The obligations of
DIHC and DIHC-MS to consummate the transactions contemplated by this Agreement
shall be subject to the fulfillment, at or prior to the Redemption Date or the
Sale Date, as applicable, of each of the following conditions unless waived by
DIHC and DIHC-MS:

                  2. The representations and warranties of C-Stone contained in
      this Agreement shall have been true and correct when made and shall be
      true and correct in all material respects as of the Redemption Date or the
      Sale Date, as applicable, with the same force and effect as if made as of
      the Redemption Date or the Sale Date, other than such representations and
      warranties as are made as of another date; the covenants and agreements
      contained in this Agreement to be complied with by C-Stone on or before
      the Redemption Date or the Sale Date, as applicable, shall have been
      complied with in all material respects, and DIHC and DIHC-MS shall have
      received a certificate from C-Stone to such effect signed by an
      appropriate officer of C-Stone. This condition shall be deemed satisfied
      unless breaches of C-Stone's representations, warranties and covenants in
      this Agreement are, in the aggregate, reasonably expected to have or have
      had a Purchaser Material Adverse Effect or adversely affect any of the
      Seller's collateral under the Purchase Money Mortgages in any material
      respect.

                  4. Other than the claims made in the Western Litigation as of
      the date hereof, no Action shall have been commenced by or before any
      Governmental Authority against any party to this Agreement, seeking to
      restrain or materially and


                                      14
<PAGE>

      adversely alter the transactions contemplated by this Agreement which, in
      the reasonable, good faith determination of DIHC and DIHC-MS, is likely to
      render it impossible or unlawful to consummate such transactions;
      provided, however, that the provisions of this Section 12.1.2 shall not
      apply if DIHC or DIHC-MS has directly or indirectly solicited or
      encouraged any such Action.

                  6. Since the date of this Agreement, there shall not have been
      any change, circumstance or event in the business or prospects of C-Stone
      which has had or would reasonably be expected to have a Purchaser Material
      Adverse Effect or adversely affect any of the Seller's collateral under
      the Purchase Money Mortgages in any material respect and DIHC shall have
      received a certificate of the chief executive officer or chief financial
      officer of C-Stone certifying to such effect.

                  8. All consents and waivers (including, without limitation,
      waivers of rights of first refusal) from third parties necessary in
      connection with the consummation of the transactions contemplated by this
      Agreement shall have been obtained, other than such consents and waivers
      from third parties, which, if not obtained, would not result individually
      or in the aggregate, in a Seller Material Adverse Effect or a Purchaser
      Material Adverse Effect.

                  10. DIHC and DIHC-MS shall have received a copy of (i) the
      Certificate of Incorporation of C-Stone certified by the Secretary of
      State of Nevada as of a date not earlier than fifteen (15) business days
      prior to the Redemption Date or Sale Date, as applicable, and accompanied
      by a certificate of the Secretary or Assistant Secretary of C-Stone, dated
      as of the Redemption Date or Sale Date, as applicable, stating that no
      amendments have been made to such Certificate of Incorporation since such
      date; and (ii) by Bylaws of C-Stone, certified by the Secretary or
      Assistant Secretary of C-Stone.

                  12. The execution of this Agreement or consummation of the
      M.I. Redemption and the DIHC Redemption will not, in the reasonable
      opinion of counsel to DIHC and DIHC-MS, result in a termination of the
      Company pursuant to Section 708 of the Internal Revenue Code of 1986, as
      amended ("IRC"). In the event counsel for DIHC and DIHC-MS reasonably
      determine that such a termination is likely to occur, DIHC, DIHC-MS and
      C-Stone agree to cooperate in good faith with each other and with M.I.
      West to restructure the transactions contemplated hereunder in such a
      mutually agreeable manner as will most closely accomplish the purpose and
      intent of the transactions contemplated hereunder without resulting in
      such a termination of the Company.

            D. Conditions to Obligations of C-Stone. The obligations of C-Stone
to consummate the transactions contemplated by this Agreement shall be subject
to the


                                      15
<PAGE>

fulfillment, at or prior to the Redemption Date or the Sale Date, as applicable,
of each of the following conditions unless waived by C-Stone:

                  2. The representations and warranties of DIHC and DIHC-MS
      contained in this Agreement shall have been true and correct when made and
      shall be true and correct in all material respects as of the Redemption
      Date or the Sale Date, as applicable, with the same force and effect as if
      made as of the Redemption Date or the Sale Date, other than such
      representations and warranties as are made as of another date; the
      covenants and agreements contained in this Agreement to be complied with
      by DIHC or DIHC-MS on or before the Redemption Date or the Sale Date, as
      applicable, shall have been complied with in all material respects, and
      C-Stone shall have received certificates from DIHC and DIHC-MS to such
      effect signed by appropriate officers thereof. This condition shall be
      deemed satisfied unless breaches of the representations, warranties and
      covenants of DIHC and DIHC-MS in this Agreement are, in the aggregate,
      reasonably expected to have or have had a Seller Material Adverse Effect.

                  4. Other than the claims made in the Western Litigation as of
      the date hereof, no Action shall have been commenced by or before any
      Governmental Authority against any party to this Agreement, seeking to
      restrain or materially and adversely alter the transactions contemplated
      by this Agreement which C-Stone believes, in its sole discretion, is
      likely to render it impossible or unlawful to consummate such transactions
      or which could have a Seller Material Adverse Effect; provided, however,
      that the provisions of this Section 12.2.2 shall not apply if C-Stone has
      solicited or encouraged any such Action.

                  6. Since the date of this Agreement, there shall not have been
      any change, circumstance or event in the Property or the business or
      prospects of the Company which has had or would reasonably be expected to
      have a Seller Material Adverse Effect and C-Stone shall have received a
      certificate of an appropriate officer of DIHC or DIHC-MS certifying to
      such effect.

                  8. All consents and waivers (including, without limitation,
      waivers of rights of first refusal) from third parties necessary in
      connection with the consummation of the transactions contemplated by this
      Agreement shall have been obtained, other than such consents and waivers
      from third parties, which, if not obtained, would not result individually
      or in the aggregate, in a Seller Material Adverse Effect or a Purchaser
      Material Adverse Effect.

                  10. C-Stone shall have received a copy of the Venture
      Agreement of the Company accompanied by a certificate of DIHC-MS dated as
      of the Redemption Date stating that no amendments have been made to such
      Venture Agreement since the date thereof.


                                      16
<PAGE>

                  12. C-Stone shall have received a rent roll with respect to
      the Property (prepared by the Property manager) certified as to knowledge
      of DIHC-MS to be true and correct in all material respects by an
      appropriate officer of DIHC-MS including a description of all Space Leases
      in effect as of the Redemption Date, the rentals payable by each tenant
      thereunder (including, without limitation, reimbursements for common area
      expenses), the original and current balance of each security deposit
      delivered under each Space Lease, and all delinquencies and defaults under
      each Space Lease.

      XXVI. Documents Upon DIHC Redemption.

            B. In addition to the documents and instruments contemplated
elsewhere in this Agreement, upon the DIHC Redemption, and as a condition
thereof, DIHC and DIHC-MS, as applicable, shall deliver:

                  2. A duly executed and acknowledged counterpart of the
      Redemption Instrument.

                  4. A duly executed and acknowledged counterpart of the
      Restated Venture Agreement.

                  6. A duly executed and acknowledged Certification
      substantially in the form attached hereto as Exhibit "D", certifying that
      the representations and warranties of DIHC and DIHC-MS set forth in
      Article 9 hereof are true and correct in all material respects as of the
      Redemption Date.

                  8. A duly executed and acknowledged Certification of
      Non-Foreign Status of DIHC-MS as described in Treasury Regulation Section
      1.1445-2(b).

                  10. A Secretary's Certificate of DIHC-MS regarding its
      Corporate Resolution to enter into the DIHC Redemption.

                  12. A Certificate of Incumbency of DIHC-MS.

                  14. A Certificate of Good Standing (or its equivalent) for
      DIHC-MS.

                  16. A Certificate of Good Standing (or its equivalent) for the
      Company.

            D. In addition to the payments, documents and instruments
contemplated elsewhere in this Agreement, upon the DIHC Redemption, and as a
condition thereof, the Company and C-Stone, as applicable, shall:



                                      17
<PAGE>

                  2. Pay the DIHC Redemption Price in accordance with and
      subject to the terms of Section 6 of this Agreement.

                  4. A duly executed and acknowledged counterpart of the
      Restated Venture Agreement.

                  6. Deliver a duly executed and acknowledged Certification
      substantially in the form attached hereto as Exhibit "E", certifying that
      the representations and warranties of C-Stone set forth in Article 10
      hereof are true and correct in all material respects as of the Redemption
      Date.

                  8. Deliver a Secretary's Certificate of C-Stone regarding its
      Corporate Resolution to enter into the DIHC Redemption.

                  10. Deliver a Certificate of Incumbency of C-Stone.

                  12. Deliver a duly executed and acknowledged counterpart of
      the Redemption Instrument.

                  14. Deliver a Certificate of Good Standing (or its equivalent)
      for C-Stone.

      XXVIII. Documents Upon Closing.

            B. In addition to the documents and instruments contemplated
elsewhere in this Agreement, upon the Closing of C-Stone's purchase of the
Retained Interest, and as a condition thereof, DIHC and DIHC-MS, as applicable,
shall deliver:

                  2. A duly executed and acknowledged counterpart of the Sale
      Instrument.

                  4. A duly executed and acknowledged Certification
      substantially in the form attached hereto as Exhibit "D", certifying that
      the representations and warranties of DIHC and DIHC-MS set forth in
      Article 9 hereof are true and correct in all material respects as of the
      Sale Date.

                  6. A duly executed and acknowledged Certification of
      Non-Foreign Status of DIHC-MS as described in Treasury Regulation Section
      1.1445-2(b).

                  8. A Secretary's Certificate of DIHC-MS regarding its
      corporation resolution to consummate the sale of the Retained Interest.


                                      18
<PAGE>

                  10.   A Certificate of Incumbency of DIHC-MS.

                  12. A Certificate of Good Standing (or its equivalent) for
      DIHC-MS.

            D. In addition to the payments, documents and instruments
contemplated elsewhere in this Agreement, upon the Closing of C-Stone's purchase
of the Retained Interest, and as a condition thereof, the Company or C-Stone, as
the case may be, shall:

                  2. Pay the cash portion of the Purchase Price to DIHC-MS or
      its designee and deliver stock certificates evidencing the C-Stone Common
      Shares to be issued to DIHC in accordance with and subject to the terms of
      Section 8 of this Agreement.

                  4. Deliver a duly executed and acknowledged Certification
      substantially in the form attached hereto as Exhibit "E", certifying that
      the representations and warranties of C-Stone set forth in Article 10
      hereof are true and correct in all material respects as of the Sale Date.

                  6. Deliver a Secretary's Certificate of C-Stone regarding its
      Corporate Resolution to consummate the purchase of Retained Interest.

                  8. Deliver a Certificate of Incumbency of C-Stone.

                  10. Deliver a duly executed and acknowledged counterpart of
      the Sale Instrument.

                  12. Deliver a Certificate of Good Standing (or its equivalent)
      for C-Stone.

                  14. Deliver a Certificate of Good Standing (or its equivalent)
      for the Company.

      XXX. Closing Costs. Except as set forth in Section 11.3, all costs
incurred by either party in connection with the closing of the transactions
hereunder, whether or not specifically mentioned herein (including, but not
limited to, legal fees and expenses in connection with the preparation,
negotiation and closing of the transactions contemplated herein or any other
transaction between the parties or their Affiliates) shall be paid for by the
party which incurred such cost or expense. The provisions of this Article 15
shall survive the consummation of the transactions contemplated herein.

      XXXII. Indemnification.


                                      19
<PAGE>

            B. Survival of Representations and Warranties. The representations
and warranties of DIHC, DIHC-MS and C-Stone contained in this Agreement shall
survive the consummation of the transactions contemplated in this Agreement
until March 31, 1999. Neither the period of survival nor the liability of either
party hereto with respect to such party's representations and warranties shall
be reduced by any investigation made at any time by or on behalf of the party
seeking indemnification. If written notice of a claim has been given prior to
the expiration of the applicable representations and warranties by the party
seeking indemnification to the other party, then the relevant representations
and warranties shall survive as to such claim until the claim has been finally
resolved.

            D. Indemnification.

                  2. C-Stone and its Affiliates (including, without limitation,
      the Company from and after the Redemption Date), officers, directors,
      employees, agents, successors and assigns (each a "C-Stone Indemnified
      Party") shall be indemnified and held harmless by DIHC and DIHC-MS for any
      and all Loss (as hereinafter defined) arising out of or resulting from the
      breach of any representation or warranty made by DIHC or DIHC-MS contained
      in this Agreement or the breach of any covenant or agreement by DIHC or
      DIHC-MS contained in this Agreement.

                  4. DIHC, DIHC-MS and their respective Affiliates, officers,
      directors, employees, agents, successors and assigns (each a "DIHC
      Indemnified Party"; a C-Stone Indemnified Party or a DIHC Indemnified
      Party sometimes herein referred to as an "Indemnified Party") shall be
      indemnified and held harmless by C-Stone for any and all Loss arising out
      of or resulting from the breach of any representation or warranty made by
      C-Stone contained in this Agreement or the breach of any covenant or
      agreement by C-Stone contained in this Agreement.

                  6. As used herein the term "Loss" or "Losses" means and
      Liabilities, losses, damages, claims, costs and expenses, interests,
      awards, judgments and penalties (including, without limitation, attorneys'
      and consultants' fees and expenses) actually suffered or incurred by any
      Indemnified Party (including, without limitation, any Action brought or
      otherwise initiated by any Indemnified Party). In the event of any Loss
      incurred by DIHC or any Affiliate thereof, for purposes of determining the
      amount DIHC is entitled to recover hereunder on account of such Loss (but
      not for purposes of determining the threshold amount of Losses or the cap
      on liability under Section 16.3), DIHC's Loss shall be "grossed up" to an
      amount equal to the quotient of (i) the amount of such Loss divided by
      (ii) a fraction the numerator of which is the aggregate number of issued
      and outstanding shares of C-Stone Common Shares and Purchaser Preferred
      Shares (as defined in the Stock Purchase Agreement) owned by Persons other
      than DIHC and PGGM as of the date on which any payment is made by C-Stone
      on account of such Loss, and the denominator of which is the


                                      20
<PAGE>

      aggregate amount of issued and outstanding C-Stone Common Shares and
      Purchaser Preferred Shares as of such date.

                  8. To the extent that either party's undertakings set forth in
      this Section 16.2 may be unenforceable, the party which is liable for the
      undertaking shall contribute the maximum amount that it is permitted to
      contribute under applicable law to the payment and satisfaction of all
      Losses incurred by the Indemnified Party.

                  10. An Indemnified Party shall give the party from which it is
      seeking indemnification hereunder (the "Indemnitor") notice of any matter
      which an Indemnified Party has determined has given or could give rise to
      a right of indemnification under this Agreement, within thirty (30) days
      of such determination, stating the amount of the Loss, if known, and
      method of computation thereof, and containing a reference to the
      provisions of this Agreement in respect of which such right of
      indemnification is claimed or arises. The obligations and liabilities of
      the Indemnitor under this Article 16 with respect to Losses arising from
      claims of any third party which are subject to the indemnification
      provided for in this Article 16 ("Third Party Claims") shall be governed
      by and contingent upon the following additional terms and conditions: if
      an Indemnified Party shall receive notice of any Third Party Claim, the
      Indemnified Party shall give the Indemnitor notice of such Third Party
      Claim within thirty (30) days of the receipt by the Indemnified Party of
      such notice; provided, however, that the failure to provide such notice
      shall not release the Indemnitor from any of its obligations under this
      Article 16 except to the extent the Indemnitor is materially prejudiced by
      such failure and shall not relieve the Indemnitor from any other
      obligation or liability that it may have to any Indemnified Party
      otherwise than under this Article 16. If the Indemnitor acknowledges in
      writing its obligation to indemnify the Indemnified Party hereunder
      against any Losses that may result from such Third Party Claim, then the
      Indemnitor shall be entitled to assume and control the defense of such
      Third Party Claim at its expense and through counsel of its choice if it
      gives notice of its intention to do so to the Indemnified Party within
      five (5) days of the receipt of such notice from the Indemnified Party;
      provided, however, that if there exists or is reasonably likely to exist a
      conflict of interest that would make it inappropriate in the reasonable
      judgment of the Indemnified Party for the same counsel to represent both
      the Indemnified Party and the Indemnitor, then the Indemnified Party shall
      be entitled to retain its own counsel, in each jurisdiction for which the
      Indemnified Party determines counsel is required, at the expense of the
      Indemnitor. In the event the Indemnitor exercises the right to undertake
      any such defense against any such Third Party Claim as provided above, the
      Indemnified Party shall cooperate with the Indemnitor in such defense and
      make available to the Indemnitor, at the Indemnitor's expense, all
      witnesses, pertinent records, materials and information in the Indemnified
      Party's possession or under the Indemnified Party's control relating
      thereto as is reasonably required by the Indemnitor. Similarly, in the
      event the Indemnified Party is, directly or indirectly, conducting the
      defense against any such Third Party


                                      21
<PAGE>

      Claim, the Indemnitor shall cooperate with the Indemnified Party in such
      defense and make available to the Indemnified Party, at the Indemnitor's
      expense, all such witnesses, records, materials and information in the
      Indemnitor's possession or under the Indemnitor's control relating thereto
      as is reasonably required by the Indemnified Party. No such Third Party
      Claim may be settled by the Indemnitor without the written consent of the
      Indemnified Party, which will not be unreasonably withheld or delayed.

            F. Limitations on Recovery. With respect to any claim for the breach
of representations and warranties hereunder, no claim may be made by an
Indemnified Party against an Indemnitor for indemnification hereunder with
respect to any individual item of Loss unless the aggregate of all Losses for
which the Indemnified Party is seeking recovery from an Indemnitor under this
Article 16 for breaches of representations or warranties plus any Losses for
which such Indemnified Party or any Affiliate thereof is seeking indemnity under
Article VII of the Stock Purchase Agreement and Article VII of the Loan Purchase
Agreement for breaches of representations or warranties shall exceed Ten Million
and No/100 Dollars ($10,000,000.00), except in the event the Indemnified Party
is seeking indemnity as a result of a wilful and intentional breach by the
Indemnitor of any of its material representations or warranties set forth in
this Agreement, in which such case the foregoing limitations shall not be
applied and the Indemnified Party shall be entitled to recover its Losses to the
full extent thereof. In the event the Indemnified Party is entitled to seek
recovery for breaches of representations or warranties hereunder, the indemnity
shall be for the full extent of all the Losses to the Indemnified Party
resulting from such breach exceeding and excluding the first $10,000,000.00
under this Agreement and the Stock Purchase Agreement and the Loan Purchase
Agreement aggregated. Notwithstanding the foregoing, the aggregate liability for
Losses for breaches or representations and warranties of any Indemnitor (and its
Affiliates) under this Article 16 and Article VII of the Stock Purchase
Agreement and Article VII of the Loan Purchase Agreement shall be limited to an
aggregate amount of One Hundred Million and No/100 Dollars ($100,000,000.00),
except in the event the Indemnified Party is seeking indemnity hereunder as a
result of the wilful and intentional breach by the Indemnitor of any of its
material representations or warranties set forth in this Agreement in which
event the foregoing limitation on liability shall not be applicable and the
Indemnified Party shall be entitled to recover its Losses to the full extent
thereof.

                  Payments made by an Indemnitor hereunder shall be limited to
the amount of the Losses that remain after deducting therefrom any insurance
proceeds and any indemnity, contribution or other payment actually received by
the Indemnified Party from any Person with respect thereto.

            H. Western Litigation. Notwithstanding the foregoing, the provisions
of this Article 16 shall not apply to any claims made by a C-Stone or DIHC
Indemnified Party with respect to the Western Litigation. Any such claim shall
be governed by and subject to that certain Indemnity Agreement of even date
herewith between DIHC and C-Stone.



                                      22
<PAGE>

      XXXIV. Termination.

            B. Termination. This Agreement may be terminated at any time prior
to the completion of the DIHC Redemption:

                  2. by mutual written consent duly authorized by the respective
      Boards of Directors of DIHC and C-Stone;

                  4. by C-Stone, upon a material breach of any representation,
      warranty, covenant or agreement on the part of DIHC or DIHC-MS set forth
      in this Agreement if such breach is reasonably expected to, or has, a
      Seller Material Adverse Effect or a Purchaser Material Adverse Effect, or
      if any material representation or warranty of DIHC or DIHC-MS shall have
      become untrue in any material respect such that the conditions set forth
      in Section 12.2 would be incapable of being satisfied prior to the
      Redemption Date;

                  6. by DIHC and DIHC-MS, upon a material breach of any
      representation, warranty, covenant or agreement on the part of C-Stone set
      forth in this Agreement if such breach is reasonably expected to, or has,
      a Purchaser Material Adverse Effect, or if any material representation or
      warranty of C-Stone shall have become untrue in any material respect such
      that the conditions set forth in Section 12.1 would be incapable of being
      satisfied prior to the Redemption Date;

                  8. by C-Stone, if any judgment, injunction, order, decree or
      action by any Governmental Authority preventing the consummation of the
      transactions contemplated hereby or requiring actions as a condition
      precedent to the consummation of such transactions which would result in a
      Purchaser Material Adverse Effect or Seller Material Adverse Effect shall
      have become final and nonappealable;

                  10. by DIHC and DIHC-MS, if any judgment, injunction, order,
      decree or action by any Governmental Authority preventing the consummation
      of the transactions contemplated hereby or requiring actions as a
      condition precedent to the consummation of such transactions which would
      result in a Purchaser Material Adverse Effect (or the impairment in any
      material respect of any of the Seller's collateral under the Purchase
      Money Mortgages) shall have become final and nonappealable; or

                  12. by C-Stone, if the M.I. Redemption Agreement is terminated
      prior to the completion of the M.I. Redemption for any reason, other than
      a default by C-Stone of its obligations under this Agreement.

            D. Effect of Termination. In the event of termination of this
Agreement as provided in Section 17.1, this Agreement shall forthwith become
void and have no effect


                                      23
<PAGE>

(except for the provisions hereof which expressly survive termination of this
Agreement, together with the definitions set forth herein which are operative
with respect to such provisions and the operative provisions hereof such as
"Notices" and "Governing Law" and the like, which shall survive termination
subject to any limitations on or survival described therein), without any
liability or obligation on the part of the parties except to the extent that
such termination results from a wilful and intentional breach by a party of any
of its material representations, warranties, covenants or agreements set forth
in this Agreement. In the event of a wilful, intentional breach by a party of
any of its material representations, warranties, covenants or agreements, the
non-defaulting party(ies) shall have the right to seek specific performance of
this Agreement and shall have the right to pursue any and all other rights or
remedies available at law, in equity or under this Agreement (including, without
limitation, to seek indemnification under Article 16) without regard to the
limitations set forth in Section 16.3.

      XXXVI. Transfer of Rights. C-Stone shall have the right to transfer its
rights under this Agreement to become the New Partner and/or to purchase the
Retained Interest to any of its Affiliates without the consent of DIHC-MS, so
that instead of C-Stone becoming the New Partner or purchasing the Retained
Interest, such Affiliate may become the New Partner, or purchase the Retained
Interest from DIHC-MS for an amount equal to the Redemption Price, and otherwise
upon the terms and conditions set forth herein; provided, however,
notwithstanding any transfer of C-Stone's rights under this Agreement to any
Affiliate, C-Stone shall remain liable with respect to all representations,
warranties, covenants, indemnities, obligations and liabilities provided by
C-Stone to DIHC-MS pursuant to the terms hereof; and provided further, however,
any such transfer of rights to an Affiliate shall only be effective in the event
the Affiliate expressly assumes the liability of C-Stone with respect to the
obligations transferred to it pursuant to the terms hereof and the Affiliate and
C-Stone shall be jointly and severally liable therefor. Any other transfer may
be denied by DIHC-MS for any reason.

      XXXVIII. Capital Calls and Indemnity. C-Stone hereby agrees that, if the
Company receives a notice after the date hereof to make a capital contribution
to MSA pursuant to the Joint Venture Agreement for MSA, DIHC-MS shall have no
obligation to fund its proportionate share of any such capital contribution and
DIHC-MS shall be relieved and released from any such obligation, unless the
closing of the DIHC Redemption or C-Stone's purchase of the Retained Interest
contemplated hereunder does not close solely due to a wilful default by DIHC.
C-Stone agrees to cause to be made any such capital contribution required from
DIHC-MS subsequent to the date hereof. C-Stone further agrees to indemnify and
hold harmless DIHC-MS and its Affiliates 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 timely make any such
capital contribution or any other matter relating to the Company, MSA, AALP
and/or the Property arising from and after the closing of the DIHC Redemption
and not caused by the wilful acts or gross negligence of DIHC or DIHC-MS. Any
such capital calls funded by C-Stone on behalf of DIHC-MS and any other


                                      24
<PAGE>

payments made by C-Stone pursuant to the indemnity in this Section 19 shall be
treated as a loan to the Company, and either treated as an advance under the
MSDI Loan, if the same can be advanced thereunder without exceeding the maximum
principal balance thereof, or as a new recourse loan to the Company to be
evidenced by a Promissory Note and Loan Agreement from the Company in favor of
C-Stone substantially in the form of Exhibit "C" annexed hereto. In the event
this Agreement is terminated solely due to a wilful default by DIHC-MS, DIHC-MS
shall reimburse C-Stone for any such loan made by C-Stone and any other payments
made by C-Stone pursuant to the indemnity under this Section 19. Except as
expressly set forth above, C-Stone hereby waives any claims it may have against
DIHC or DIHC-MS, if any, for failure on the part of DIHC or DIHC-MS or any
Affiliate thereof to fund or make captial contributions to the Company.

      XL. Notices. All notices, demands, or requests ("Notices") required or
desired to be given hereunder shall be given in writing and sent in the manner
provided under the Venture Agreement except that:

            B. Notices to DIHC and DIHC-MS (and to the Company prior to the
closing of the DIHC Redemption) shall be sent to the address for DIHC set forth
above, Attention: Mr. Robert T. Sorrentino, with a copy sent in like manner to
Richards & O'Neil, LLP, 885 Third Avenue, New York, New York 10022, Attention:
Robert M. Safron, Esq.; and

            D. Notices to C-Stone (and to the Company after the date of the
closing of the DIHC Redemption) shall be sent to the address for C-Stone set
forth above, Attention Mr. John S. Moody, with a copy sent in like manner to
King & Spalding, 191 Peachtree Street, N.E., Atlanta, Georgia 30303, Attention:
William B. Fryer, Esq.

      XLII. Broker. Each party represents and warrants to the other that there
is no broker in connection with this transaction and hereby agrees to indemnify,
save harmless and defend the other from and against all claims, losses,
liabilities and expenses, including reasonable attorneys' fees, arising out of
any claim made by a broker, finder or other intermediary who claims to have been
engaged by such party in connection with the transaction which is the subject of
this Agreement. The provisions of this Article 21 shall survive the Closing
Date.

      XLIV. Miscellaneous.

            B. Subject to the limitations on assignment set forth herein, the
provisions of this Agreement shall inure to the benefit of and bind the heirs,
executors, administrators, successors and assigns of the respective parties.

            D. This Agreement shall be governed by, and construed in accordance
with, the laws of the District of Columbia.


                                      25
<PAGE>

            F. The parties shall each execute, acknowledge and deliver to the
others such instruments and take such action, in addition to the instruments and
actions provided for herein, as the others may reasonably request in order to
effectuate the express purposes or provisions of this Agreement or the
transactions contemplated hereunder.

            H. Each party hereby represents that, except as set forth in this
Agreement or in the other instruments and documents executed and delivered
pursuant to this Agreement, no party has made any representations or warranties
to any other party with respect to the Interest, the Retained Interest or the
Company.

            J. The invalidity or unenforceability of any one or more provisions
of this Agreement shall in no way affect any other provisions of this Agreement.

            L. To the extent there are any warranties, representations,
agreements, obligations, guaranties or benefits (collectively, the "Benefits")
which inure to the benefit of the Company from any Person or governmental
authority, effective as of the Redemption Date, DIHC-MS shall assign to the
Company (without any representation, warranty or recourse whatsoever) all of the
right, title and interest of DIHC-MS, if any, in the Benefits, except to the
extent any of the Benefits relates to the Retained Interest, and as of the Sale
Date, DIHC-MS shall assign to C-Stone (without any representation, warranty or
recourse whatsoever) all of the right, title and interest of DIHC-MS, if any, in
the Benefits relating to the Retained Interest.

            N. Upon the closing of the DIHC Redemption, DIHC-MS shall be deemed
to have waived any rights and/or privileges that it has or may have under
Articles VII and VIII of the Venture Agreement. The Company represents and
warrants that it has not received any notices from the other venturer in MSA
exercising any rights under such Articles. Upon the closing of the DIHC
Redemption, DIHC-MS shall be deemed to have further waived any rights it may
have under the Venture Agreement with respect to Major Decisions (as defined in
the Venture Agreement) or otherwise relating to the management or decision
making process under the Venture Agreement.

            P. This Agreement may not be modified or amended except by a written
agreement signed by the parties hereto.

            R. This Agreement, together with the Schedules and Exhibits attached
hereto and the Stock and Loan Purchase Agreements, sets forth the entire
agreement between the parties hereto with respect to the subject matter hereof
and all prior understandings or communications (written or oral) between the
parties with respect thereto are merged in this Agreement.

            T. Except as otherwise provided herein, nothing in this Agreement is
intended, nor shall anything herein be construed, to confer any rights, legal or
equitable, in any Person other than the parties hereto and their respective
successors and permitted assigns.

            V. This Agreement may be signed in counterparts by the parties and
shall be binding and effective upon the parties even if so signed and delivered.


                                      26
<PAGE>

            X. Except as otherwise provided in this Agreement, the provisions of
this Agreement shall survive the consummation of the transactions contemplated
hereunder.

            Z. Closing the Books. The parties agree that profits and losses of
the Company shall be allocated based upon the closing of the books method
described in IRC ss.706(d)(2).


                                      27
<PAGE>

      IN WITNESS WHEREOF, parties hereto have hereunto set their hands and seals
the day and year above written.

                              Company:

                              MARKET SQUARE DEVELOPMENT INVESTORS,
                              a District of Columbia general partnership

                              By:   DIHC MARKET SQUARE, INC., a Georgia
                                    corporation, as authorized general partner

                                    By:/s/ Robert T. Sorrentino
                                       -----------------------------------
                                            Name: Robert T. Sorrentino
                                            Title: Vice President

                              DIHC:

                              DUTCH INSTITUTIONAL HOLDING COMPANY,
                              INC., a Delaware corporation

                                    By:/s/ Robert T. Sorrentino
                                       -----------------------------------
                                       Name: Robert T. Sorrentino
                                       Title: Vice President

                              DIHC-MS:

                              DIHC MARKET SQUARE, INC., a Georgia
                              corporation

                                    By:/s/ Robert T. Sorrentino
                                       -----------------------------------
                                       Name: Robert T. Sorrentino
                                       Title: Vice President


                                      1
<PAGE>

                              C-Stone:

                              CORNERSTONE PROPERTIES INC., a Nevada
                              corporation

                                    By:/s/ John S. Moody
                                       -----------------------------------
                                       Name: John S. Moody
                                       Title:  President

                                    By:/s/ Rodney C. Dirreck
                                       -----------------------------------
                                       Name: Rodney C. Dirreck
                                       Title:  Executive Vice President



                                      2
<PAGE>

                                   Schedule A

AVENUE ASSOCIATES LIMITED PARTNERSHIP

Third Amended and Restated Agreement of Limited Partnership for Avenue
Associates Limited Partnership, dated July 15, 1987, Market Square Associates,
as general partner, Market Square Associates, as Class A limited partner, and
Western Associates Limited Partnership, as Class B limited partner.

MARKET SQUARE ASSOCIATES

(a) Joint Venture Agreement for Market Square Associates, dated May 21, 1987, by
and among Crow-Pennsylvania Avenue Limited Partnership and DIHC Market Square,
Inc.

(b) Addendum to Joint Venture Agreement For Market Square Associates, dated May
21, 1987, by and among Crow-Pennsylvania Avenue Limited Partnership and DIHC
Market Square, Inc.

(c) Amendment to Joint Venture Agreement For Market Square Associates, dated
July 15, 1987, by and among Crow-Pennsylvania Avenue Limited Partnership and
DIHC Market Square, Inc.

(d) First Amendment to Joint Venture Agreement For Market Square Associates,
dated January 27, 1989, by and among Crow-Pennsylvania Avenue Limited
Partnership and DIHC Market Square, Inc.

(e) Second Amendment to Joint Venture Agreement For Market Square Associates,
dated April 17, 1991, by and among Crow-Pennsylvania Avenue Limited Partnership
and Mar quare Development Investors.

(f) Third Amendment to Joint Venture Agreement For Market Square Associates,
dated January 4, 1994, by and among Crow-Pennsylvania Avenue Limited Partnership
and Market Square Development Investors.

<PAGE>

                                                                     EXHIBIT "A"

                    INSTRUMENT OF REDEMPTION AND ASSUMPTION

      DIHC MARKET SQUARE, INC., a Georgia corporation, having an address at 200
Galleria Parkway, N.W., Suite 2000, Atlanta, Georgia 30339 (the "DIHC-MS"), in
consideration of the sum of Ten Dollars ($10.00) and other good and valuable
consideration, the receipt and legal sufficiency of which is hereby
acknowledged, hereby transfers to MARKET SQUARE DEVELOPMENT INVESTORS, a
District of Columbia general partnership having an office at 126 East, 56th
Street, New York, New York 10022 (the "Company"), all of the right, title and
interest of DIHC-MS as a partner in the Company, and all of the rights of
DIHC-MS to the assets and profits thereto and distributions therefrom, to have
and to hold the same unto the Company from and after the date hereof (the
"Redeemed Interest"), provided that DIHC-MS shall retain one percent (1%) of the
total interest in the Company.

      All capitalized terms used herein and not otherwise defined shall have the
meaning given to them in that certain Redemption and Acquisition Agreement dated
as of October _, 1997 between Inc. (the "Redemption Agreement").

      The Company and DIHC-MS each hereby covenant and agree to file all
necessary certificates and/or amendments to the Partnership Agreement in the
District of Columbia or other governmental subdivisions in which the Company has
done or is doing business to reflect the redemption of the Redeemed Interest,
and to execute and deliver the Restated Venture Agreement in accordance with the
terms of the Redemption Agreement.

      The transfer of the Redeemed Interest is without representation by or
recourse against DIHC-MS except as set forth in the Redemption Agreement.

      This Instrument shall be binding upon and inure to the benefit of the
parties hereto and their respective representatives, successors and assigns.

      This Instrument shall be governed by, and construed in accordance with,
the laws of the District of Columbia.


                                      A-1
<PAGE>

      IN WITNESS WHEREOF, DIHC-MS and the Company have caused this Instrument to
be executed and delivered by its duly authorized officers as of the day of
January, 1998.

                                  DIHC MARKET SQUARE, INC., a Georgia
                                  corporation

                                  By:
                                     -----------------------------------
                                        Name: __________________________
                                        Title: _________________________

                                  MARKET SQUARE DEVELOPMENT INVESTORS,
                                  a District of Columbia general partnership

                                  By:   CORNERSTONE PROPERTIES INC., a
                                        Nevada corporation, as managing general
                                        partner

                                        By:
                                              --------------------------
                                              Name: ____________________
                                              Title: ___________________

STATE OF NEW YORK       )
                        )     ss.:
COUNTY OF NEW YORK      )

      On the ___ day of January, 1998, before me personally came _________, to
me known who, being by me duly sworn, did depose and say that he resides at
___________________ ____________, that he is the ________ President of DIHC
MARKET SQUARE, INC., the corporation described in and which executed the
foregoing instrument; and that he signed his name thereto by order of the Board
of Directors of said corporation.


                                    _________________________________
                                    Notary Public



                                      A-2
<PAGE>

STATE OF NEW YORK       )
                        )     ss.:
COUNTY OF NEW YORK      )

      On the ____ day of January, 1998, before me personally came _____________,
to me known who, being by me duly sworn, did depose and say that he resides at
_______________ ___________________, that he is the _______ President of
CORNERSTONE PROPERTIES INC., the corporation described in and which executed the
foregoing instrument, acting in its capacity as the managing general partner of
MARKET SQUARE DEVELOPMENT INVESTORS, the general partnership described in and
which executed the foregoing instrument; and that he executed the foregoing
instrument by order of the Board of Directors of said corporation, as and for
the act and deed of said general partnership.


                                  _________________________________
                                  Notary Public



                                      A-3
<PAGE>

                                                                     EXHIBIT "B"

                       INSTRUMENT OF SALE AND ASSUMPTION

      DIHC MARKET SQUARE, INC., a Georgia corporation, having an address at 200
Galleria Parkway, N.W., Suite 2000, Atlanta, Georgia 30339 (the "DIHC-MS"), in
consideration of the sum of Ten Dollars ($10.00) and other good and valuable
consideration, the receipt and legal sufficiency of which is hereby
acknowledged, hereby bargains, sells, transfers and sets over to CORNERSTONE
PROPERTIES INC., a Nevada corporation having an office at 126 East 56th Street,
New York, New York 10022 ("C-Stone"), all of the right, title and interest of
DIHC-MS as a partner in MARKET SQUARE DEVELOPMENT INVESTORS, a District of
Columbia general partnership (the "Company"), and all of the rights of DIHC-MS
to the assets and profits thereto and distributions therefrom, to have and to
hold the same unto C-Stone from and after the date hereof (the "Transferred
Interest").

      All capitalized terms used herein and not otherwise defined shall have the
meaning given to them in that certain Redemption and Acquisition Agreement dated
as of October__, 1997 between the Company, Dutch Institutional Holding Company,
Inc.. DIHC-MS, and Cornerstone Properties Inc. (the "Redemption Agreement").

      C-Stone and DIHC-MS each hereby covenant and agree to file all necessary
certificates and/or amendments to the Partnership Agreement in the District of
Columbia or other governmental subdivisions in which the Company has done or is
doing business to reflect the sale and transfer of the Transferred Interest.

      The transfer of the Transferred Interest is made without representation by
or recourse against DIHC-MS except as set forth in the Redemption Agreement.

      This Instrument shall be binding upon and inure to the benefit of the
parties hereto and their respective representatives, successors and assigns.

      This Instrument shall be governed by, and construed in accordance with,
the laws of the District of Columbia.


                                      B-1
<PAGE>

      IN WITNESS WHEREOF, DIHC-MS and C-Stone have caused this Instrument to be
executed and delivered by its duly authorized officers as of the ___ day of.
_____________, ____

                                       DIHC MARKET SQUARE, INC., a Georgia
                                       corporation

                                       By:
                                             ---------------------------------
                                             Name: ___________________________
                                             Title: __________________________

                                       CORNERSTONE PROPERTIES INC., a
                                       Nevada corporation, as managing general
                                       partner

                                       By:
                                             ---------------------------------
                                             Name: ___________________________
                                             Title: __________________________

STATE OF NEW YORK       )
                        )     ss.:
COUNTY OF NEW YORK      )

      On the ____ day of _______, ___, before me personally came _____________,
to me known who, being by me duly Sworn, did depose and say that he resides at
______________ ______________________, that he is the President of DIHC MARKET
SQUARE, INC., the corporation described in and which executed the foregoing
instrument; and that he signed his name thereto by order of the Board of
Directors of said corporation.

                                    __________________________________
                                    Notary Public


                                      B-2
<PAGE>

STATE OF NEW YORK       )
                        )     ss.:
COUNTY OF NEW YORK      )

      On the _____ day of _________, ___, before me personally came to
_____________, to me known who, being by me duly sworn, did depose and say that
he resides at _____________ ________________, that he is the _______ President
of CORNERSTONE PROPERTIES INC., the corporation described in and which executed
the foregoing instrument; and that he executed the foregoing instrument by order
of the Board of Directors of said corporation.

                                    __________________________________
                                    Notary Public


                                      B-3
<PAGE>

                                                                     EXHIBIT "C"

                       PROMISSORY NOTE AND LOAN AGREEMENT

Principal Sum: $_____________                           Date:  January ___, 1998
                                                              New York, New York

      FOR VALUE RECEIVED, MARKET SQUARE DEVELOPMENT INVESTORS ("Maker"), a
District of Columbia limited partnership, promises to pay to CORNERSTONE
PROPERTIES INC. ("Payee"), a Nevada corporation having an office at 126 East
56th Street, New York, New York 10022, or to order, or at such other place as
may be designated in writing by the holder hereof, the principal sum of
______________________________ AND NO/100 DOLLARS ($________________) with
interest thereon, or on the amount thereof from time to time outstanding, to be
computed as hereinafter provided, until the said principal sum shall be fully
paid, to be due and payable as hereinafter provided. The said principal sum, or
the amount thereof outstanding, with accrued and unpaid interest thereon, shall
be due and payable on the Maturity Date (as hereinafter defined).

      1. Interest. Interest shall accrue from the date hereof to and through the
date on which all principal and interest hereunder is paid in full, shall be
computed on the basis of actual days elapsed in a 365-day year, and shall be
calculated on the outstanding principal balance hereunder at an annual rate of
interest equal to eleven percent (11%) percent per annum (the "Interest Rate").

      2. Installments.

            a. No installments of interest or principal shall be payable under
this Note for the period commencing on the date hereof and ending on August 1,
1999 (the "Deferral End Date"). During such period, all interest on this Note
shall accrue and, to the extent permitted by law, such accrued and unpaid
interest shall bear interest at the Interest Rate, compounded monthly.


                                      C-1
<PAGE>

            b. Installments of principal and interest at the Interest Rate (the
"Installment Payments"), in the amount necessary to amortize in equal monthly
payments the sum of (a) the then-outstanding principal sum hereof and (b) the
amount of all interest accrued and deferred pursuant to the preceding sentence
as of the Deferral End Date, and the interest accrued thereon as of Deferral End
Date, less any sums paid on account of such accrued and deferred interest and on
account of principal as hereinafter provided, together with interest on such
sum, over a period of twenty (20) years (the "Amortization Period"), shall be
due and payable commencing on September 1, 1999 and continuing on the first day
of each and every calendar month thereafter ensuing until September 1, 2002 (the
"Maturity Date"), at which time the entire outstanding principal sum hereof, all
accrued interest and all other sums due and payable hereunder shall be fully
paid. Payee shall calculate the amount of such installments and give notice
thereof to Maker. Payee's calculation of the amount of such installments shall
be definitive absent manifest error.

            c. Maker agrees that in the event that Maker has any net cash flow
from any source, such net cash flow shall be applied first on account of any
interest accrued and deferred hereunder; second, on account of any Installment
Payments then due hereunder; and third, on account of the outstanding principal
amount of this Note prior to being used for any other purpose.

            d. Payee expressly acknowledges that (i) in no event shall the
obligations of Maker under this Note or the Security Documents (as hereinafter
defined) be enforced against DIHC Market Square, Inc. ("DIHC-MS"), any interest
of DIHC-MS in Maker, or any shareholder, officer, director or agent of DIHC-MS
(collectively, the "Exculpated Parties") and (ii) Payee shall not seek any
judgment against the Exculpated Parties in respect of this Note, the Security
Documents or otherwise relating to the indebtedness evidenced hereby.


                                      C-2
<PAGE>

      3. Default Interest Rate. In the event Maker fails to pay any installment
of principal or interest within ten (10) days after its due date, the unpaid
amount shall accrue interest at the rate (the "Default Rate") equal to the
lesser of (a) five percent (5%) in excess of the "prime rate" announced from
time to time by Bankers Trust Company at its offices in the City of New York or
(b) the maximum interest rate permitted by law to be charged to Maker until
paid.

      4. Security. Upon the request of Payee, Maker shall deliver (a) to Payee a
pledge of Maker's partnership interest under the joint venture agreement for
Market Square Associates, a District of Columbia general partnership ("MSA"), as
security for Maker's obligations under this Note pursuant to a pledge and
security agreement satisfactory to Payee, and (b) such other security documents
as Payee may reasonably request to secure Maker's obligations hereunder,
including, but not limited to, UCC-1 Financing Statements (collectively, the
"Security Documents").

      5. Event of Default. The occurrence of any one of the following events
shall constitute an "Event of Default" hereunder:

            a. Maker fails to pay any installment of principal or interest, or
any other sum due hereunder, when and as the same shall become due and payable,
and such failure is not cured within fifteen (I 5) days after written notice
thereof from Payee to Maker;

            b. Maker, or any endorser makes any assignment for the benefit of
creditors; or a receiver, liquidator or trustee of Maker, or of substantially
all property of Maker or such endorser, is appointed; or any voluntary or
involuntary petition for the bankruptcy, reorganization or arrangement of, or
for the composition, extension, arrangement or adjustment of any of the
obligations of, Maker or such endorser, pursuant to the Federal Bankruptcy Code,
or any similar statute, is filed and not dismissed within 60 days; or Maker or
such endorser shall have been adjudicated a bankrupt or insolvent; or any
voluntary or involuntary petition by or against Maker or such endorser, as
debtor


                                      C-3
<PAGE>

seeking an order for relief pursuant to the Federal Bankruptcy Code, or any
similar statute, is pending or filed and not dismissed within 60 days; or a
court enters an order for relief for Maker or such endorser, as debtor; or Maker
or any such endorser, is insolvent by reason of its inability to pay its debts
as they become due; or a writ of attachment is issued against any of the
property of Maker or such endorser, and not dismissed within 60 days-, or if
possession is taken to assume control of all or any substantial part of such
part of such property or of the business of Maker or such endorser by any
government or governmental agency; and/or

            c. Any warranty, representation or statement of Maker in this Note
or any of the Security Documents or any other instrument or document now or
hereafter evidencing, securing or otherwise relating to the indebtedness
evidenced by this Note proves untrue or misleading in any material respect; or
Maker fails to keep, observe, and perform any other covenant, agreement,
obligation or condition contained herein, the Security Documents or in any other
instrument or document now or hereafter evidencing or securing the indebtedness
evidenced by this Note or any part thereof, and such untruth, misleading matter,
failure or default is not cured within thirty (30) days after written notice
thereof from Payee to Maker or such additional period as may be reasonably
needed as long as Payee commences the cure of same within the thirty (30) day
period and thereafter diligently prosecutes the cure to completion.

      6. Rights of Payee upon Default. Upon and after the occurrence of an Event
of Default, it is expressly agreed that the principal sum of this Note (and all
accrued interest thereon and other sums payable hereunder) shall become
immediately due and payable at the option of Payee.

      7. Prepayment. This Note may be prepaid in whole or in part without fee or
penalty (but with accrued interest on the amount so prepaid) at any time upon
not less than ten (10) days' prior written notice by Maker to Payee.


                                      C-4
<PAGE>

      8. Applicable Law. This Note has been negotiated, executed, made and
delivered in the City, Country and State of New York. Maker agrees that this
Note shall be governed, construed and interpreted in accordance with the laws of
the State of New York.

      9. Waiver.

            a. Maker and any endorsers, sureties and guarantors hereof or hereon
hereby waive presentment for payment, demand, protest, notice of non-payment or
dishonor and of protest, and agree to remain bound until the principal sum of
this Note or the amount thereof outstanding and interest and all other sums
payable hereunder are paid in full notwithstanding any extensions of time for
payment which may be granted, even though the period of extension may be
indefinite, and notwithstanding any inaction by, or failure to assert any legal
right available to, Payee.

            b. It is further expressly agreed that any waiver by Payee, other
than a waiver in writing signed by Payee, of any term or provision hereof, of
the Security Documents or of any right, remedy or option under this Note or the
Security Documents shall not be controlling, nor shall it prevent or estop Payee
from thereafter enforcing such term, provision, right, remedy or option, and the
failure or refusal of Payee to insist in any one or more instances upon the
strict performance of any of the terms or provisions of this Note, or the
Security Documents shall not be construed as a waiver or relinquishment for the
future of any such term or provision, but the same shall continue in full force
and effect, it being understood and agreed that Payee's rights, remedies and
options under this Note and the Security Documents are and shall be cumulative
and are in addition to all other rights, remedies and options of Payee at law or
in equity or under any other agreement.

            c. No modification or waiver by Payee of any right or remedy under
this Note shall be effective unless made in writing. No delay by Payee in
exercising any right or remedy hereunder, or otherwise afforded by law, shall
operate as a waiver thereof or preclude the exercise thereof upon


                                      C-5
<PAGE>

the occurrence of an Event of Default. No failure by Payee to insist upon the
strict performance by Maker of each and every covenant and agreement of Maker
under this Note shall constitute a waiver of any such covenant or agreement, and
no waiver by Payee of any Event of Default shall constitute a waiver of or
consent to any subsequent Event of Default. No failure of Payee to exercise its
option to accelerate the maturity of the indebtedness evidenced hereby, nor any
forbearance by Payee before or after the exercise of such option shall be
construed as a waiver of an option, power, right or remedy of Payee hereunder.

      10. Successors. The term "Payee" shall mean the then holder of this Note
from time to time and its successors and permitted assigns.

      11. Costs of Collection. Maker shall pay all costs of collection when
incurred, including, without limitation, the reasonable attorneys' fees and
disbursements of the Payee's counsel and court costs, which costs may be added
to the indebtedness evidenced hereby and must be paid promptly on demand,
together with interest thereon at the Default Rate.

      12. Interest Not to Exceed Maximum Allowed by Law. If from any
circumstances whatsoever, the fulfillment of any provision of this Note or of
any other instrument evidencing or securing the indebtedness evidenced hereby,
at the time performance of such provision shall be due, shall involve
transcending the limit of validity presently prescribed by any applicable usury
statute or any other applicable law with regard to obligations of like character
and amount, then ipso facto, the obligation to be fulfilled shall be reduced to
the limit of such validity so that in no event shall any exaction be possible
under this Note or under any other instrument evidencing or securing the
indebtedness evidenced hereby that is in excess of the current limit of such
validity, but such obligation shall be fulfilled to the limit of such validity.
In the event of any such reduction of said obligation, the unpaid principal
balance of this Note together with all accrued interest thereon and any other
sums


                                      C-6
<PAGE>

advanced hereunder or under any instruments securing the indebtedness evidenced
hereby shall at the option of Payee become immediately due and payable.

      13. Assignment. Payee's right, title and interest in and to this Note are
freely assignable by Payee to Cornerstone Properties Inc. ("CPP"), or any
affiliate or subsidiary of CPP without the consent or approval of any person or
entity, and any such assignment hereof by Payee shall operate to vest in such
assignee all rights, titles, interests and powers herein conferred upon Payee.
Notwithstanding the foregoing, Maker acknowledges that Payee may, at any time
and from time to time, sell this Note or any interest herein, pledge or assign
this Note or any interest herein as security in connection with any financing
arrangement and enter into any participation or similar cooperative arrangements
with respect hereto.

      14. Time of the Essence. Time is of the essence with respect to each and
every covenant, agreement and obligation of Maker under this Note.

      15. Successors and Assigns. Each and every covenant, warranty and
agreement of Maker herein, if Maker be more than one, shall be jointly and
severally binding upon and enforceable against Maker, and each of them except as
otherwise provided in this Note. As used herein the terms "Maker" and "Payee"
shall include the Maker and the named Payee and their respective heirs,
executors, administrators, legal representatives, successors, successors in
title and permitted assigns.

      16. Severability. If any provision, paragraph, sentence, clause, phrase or
word of this Note, or the application thereof in any circumstance, is held
invalid or unenforceable, the validity and enforceability of the remainder of
this Note, and of the application of any such provision, paragraph, sentence,
clause, phrase or word in any other circumstance, shall not be affected thereby,
it being intended that all rights, powers and privileges of Payee hereunder
shall be enforceable to the fullest extent permitted by law.


                                      C-7
<PAGE>

      17. Notices. Any and all notices, elections or demands permitted or
required to be made under this Note (collectively, "Notices") shall be in
writing and shall be delivered personally, or sent by registered or certified
mail, to the other party at the address set forth above, or at such other
address as may be supplied in writing in accordance with the terms of this
paragraph. The date of personal delivery, the third (3rd) business day following
the date of mailing or the first (1st) business day following a transmission by
overnight courier, as the case may be, shall be the date of the Notice.

      18. Captions. Titles or captions of articles and paragraphs contained in
this Note are inserted only as a matter of convenience and for reference, and in
no way define, limit, extend or describe the scope of this Note or the intent of
any provision hereof.

      19. Number and Gender. Whenever required by the context, the singular
number shall include the plural and the gender of any pronoun shall include the
other genders.

      IN WITNESS WHEREOF, Maker has executed this Note as of the ___ day of
January, 1998.

                                MARKET SQUARE DEVELOPMENT
                                INVESTORS, a District of Columbia general
                                partnership

                                By:   CORNERSTONE PROPERTIES INC., a
                                      Nevada corporation, as authorized general
                                      partner

                                      By:
                                            -------------------------------
                                            Name: _________________________
                                            Title: ________________________

                                By:   DIHC MARKET SQUARE, INC., a
                                      Georgia corporation, general partner

                                      By:
                                            -------------------------------
                                            Name: _________________________
                                            Title: ________________________



                                      C-8
<PAGE>

                                                                     EXHIBIT "D"

                                 CERTIFICATION

      The undersigned hereby certifies that all of the representations and
warranties made by it pursuant to Article 9 of that certain Redemption and
Acquisition Agreement dated as of October __, 1997 between Market Square
Development Investors, Dutch Institutional Holding Company, Inc., DIHC Market
Square, Inc., and Cornerstone Properties Inc. are true and correct in all
material respects as of this day, except as set forth on Schedule I annexed
hereto.

Dated: as of the ____ day of _________, ____

                                      DIHC MARKET SQUARE, INC., a Georgia
                                      corporation

                                      By:
                                            -------------------------------
                                            Name: _________________________
                                            Title: ________________________

STATE OF NEW YORK       )
                        )     ss.:
COUNTY OF NEW YORK      )

      On the ____ day of _________, ____, before me personally came
_____________, to me known who, being by me duly sworn, did depose and say that
he resides at ________________ ______________________________, that he is the
________ President of DIHC MARKET SQUARE, INC., the corporation described in and
which executed the foregoing instrument; and that he signed his name thereto by
order of the Board of Directors of said corporation.


                                    ______________________________
                                    Notary Public


                                      D-1
<PAGE>

                                                                     EXHIBIT "E"

                                  CERTIFICATION

      The undersigned hereby certifies that all of the representations and
warranties made by it pursuant to Article 10 of that certain Redemption and
Acquisition Agreement dated as of October __, 1997 between Market Square
Development Investors, Dutch Institutional Holding Company, Inc., DIHC Market
Square, Inc., and Cornerstone Properties Inc. are true and correct in all
material respects as of this day, except as set forth on Schedule I annexed
hereto.

Dated: as of the ____ day of _________, ____

                     CORNERSTONE PROPERTIES, INC., a Nevada

                                    corporation

                                      By:
                                            -------------------------------
                                            Name: _________________________
                                            Title: ________________________

STATE OF NEW YORK       )
                        )     ss.:
COUNTY OF NEW YORK      )

      On the ____ day of _________, ____, before me personally came
_____________, to me known who, being by me duly sworn, did depose and say that
he resides at ________________ ______________________________, that he is the
________ President of CORNERSTONE PROPERTIES, INC., the corporation described in
and which executed the foregoing instrument; and that he signed his name thereto
by order of the Board of Directors of said corporation.


                                    _______________________________________
                                    Notary Public


                                      E-1