<PAGE>
                                                                  Exhibit 10.96

                      NOTE AND COLLATERAL AGENCY AGREEMENT

                       dated as of October 27, 1997, among

                          CORNERSTONE PROPERTIES INC.,

                    certain of its SUBSIDIARIES party hereto,

                            the LENDERS party hereto,

                                       and

                   STICHTING PENSIOENFONDS VOOR DE GEZONDHEID,
               GEESTELIJKE EN MAATSCHAPPELIJKE BELANGEN ("PGGM"),
                             as Administrative Agent


The parties hereto agree as follows:

                                 ARTICLE  I.

                                  Definitions

            SECTION 1.1 Defined Terms. As used in this Note and Collateral
Agency Agreement as amended, supplemented or modified hereafter (the
"Agreement"), the following terms have the meanings specified below:

            "Administrative Agent" means Stichting Pensioenfonds voor de
Gezondheid, Geestelijke en Maatschappelijke Belangen, in its capacity as
administrative agent for the Lenders hereunder.

            "Affiliate" means, with respect to a specified Person, another
Person that directly, or indirectly through one or more intermediaries, Controls
or is Controlled by or is under common Control with the Person specified. With
respect to natural persons, all individuals related by blood, marriage or
adoption shall be deemed to be an Affiliate of such natural person. For purposes
of this Agreement, the Administrative Agent and the Lenders shall not be
Affiliates of the Borrower or any of Borrower's Subsidiaries.

            "Assignment and Acceptance" means an assignment and acceptance
entered into by a Lender and an assignee (with the consent of any party whose
consent is required by Section 8.5), and accepted by the Administrative Agent.

            "Board of Directors" means the board of directors of Borrower or any
committee of that board duly authorized to act hereunder.
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                                      2

            "Borrower" means Cornerstone Properties Inc., a Nevada corporation.

            "Bryce Security Documents" shall mean that certain Deed of Trust and
Security Agreement dated as of the date hereof executed by Bryce Mountain, Inc.
in favor of Administrative Agent, that certain Assignment of Lessor's Interest
in Leases dated as of the date hereof executed by Bryce Mountain, Inc. in favor
of Administrative Agent, that certain Environmental Indemnification Agreement
dated as of the date hereof executed by Bryce Mountain, Inc. in favor of
Administrative Agent, that certain Stock Pledge Agreement (Bryce Mountain, Inc.)
dated as of the date hereof executed by Borrower in favor of Administrative
Agent and any other document, instrument or agreement securing or otherwise
evidencing the obligations in respect of the Guaranty including UCC financing
statements.

            "Business Day" means any day that is not a Saturday, Sunday or other
day on which commercial banks in New York City are authorized or required by law
to remain closed.

            "Capital Lease Obligations" of any Person means the obligations of
such Person to pay rent or other amounts under any lease of (or other
arrangement conveying the right to use) real or personal property, or a
combination thereof, which obligations are required to be classified and
accounted for as capital leases on a balance sheet of such Person under GAAP,
and the amount of such obligations shall be the capitalized amount thereof
determined in accordance with GAAP.

            "Charlotte Office Security Documents" shall mean that certain Deed
of Trust and Security Agreement dated as of the date hereof executed by
Charlotte Office Tower Associates in favor of Administrative Agent, that certain
Assignment of Lessor's Interest in Leases dated as of the date hereof executed
by Charlotte Office Tower Associates in favor of Administrative Agent, that
certain Environmental Indemnification Agreement dated as of the date hereof
executed by Charlotte Office Tower Associates in favor of Administrative Agent,
that certain Stock Pledge Agreement (Charlotte Plaza Properties, Inc.) dated as
of the date hereof executed by Borrower in favor of Administrative Agent, that
certain Stock Pledge Agreement (Balsam Mountain, Inc.) dated as of the date
hereof executed by Borrower in favor of Administrative Agent, that certain
Assignment and Security Agreement (Charlotte Office Tower Associates) dated as
of the date hereof executed by Charlotte Plaza Properties, Inc. in favor of
Administrative Agent, and that certain Assignment and Security Agreement
(Charlotte Office Tower Associates) dated as of the date hereof executed by
Balsam Mountain, Inc. in favor of Administrative Agent and any other document,
instrument or agreement securing or otherwise evidencing the obligations in
respect of the Guaranty including UCC financing statements.

            "Collateral" means all property and assets, now existing or
hereafter acquired, and all cash and non-cash proceeds thereof, in respect of
which any Lien in favor of Lenders is granted or created under the terms of any
of the Collateral Agreements.
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                                      3

            "Collateral Agreements" means, collectively, the Note A Collateral
Agreements, the Note B Collateral Agreements, the Note C Collateral Agreements,
the Note D Collateral Agreements and the Note E Collateral Agreements.

            "Collateral Note Documents" shall mean that certain Collateral
Assignment of Mortgage and Other Documents (Market Square) dated as of the date
hereof executed by Borrower in favor of Administrative Agent and that certain
Collateral Assignment of Note dated as of the date hereof executed by Borrower
in favor of Administrative Agent.

            "Commission" means the Securities and Exchange Commission, as from
time to time constituted, created under the Exchange Act.

            "Control" means the possession, directly or indirectly, of the power
to direct or cause the direction of the management or policies of a Person,
whether through the ability to exercise voting power, by contract or otherwise.
"Controlling" and "Controlled" have meanings correlative thereto.

            "Dearborn Security Documents" shall mean that certain Mortgage and
Security Agreement dated as of the date hereof executed by Dearborn Interests in
favor of Administrative Agent, that certain Assignment of Lessor's Interest in
Leases dated as of the date hereof executed by Dearborn Interests in favor of
Administrative Agent, that certain Environmental Indemnification Agreement dated
as of the date hereof executed by Dearborn Interests in favor of Administrative
Agent; that certain Stock Pledge Agreement (DIHC Marble Place Properties, Inc.)
dated as of the date hereof executed by Borrower in favor of Administrative
Agent; that certain Stock Pledge Agreement (DIHC Dearborn Properties, Inc.)
dated as of the date hereof executed by Borrower in favor of Administrative
Agent; that certain Assignment and Security Agreement (DIHC Dearborn Venture)
dated as of the date hereof executed by DIHC Marble Place Properties, Inc, in
favor of Administrative Agent; that certain Assignment and Security Agreement
(DIHC Dearborn Venture) dated as of the date hereof executed by DIHC Dearborn
Properties, Inc. in favor of Administrative Agent; that certain Assignment of
Security Agreement (Dearborn Interests) dated as of the date hereof executed by
DIHC Dearborn Properties, Inc. in favor of Administrative Agent; that certain
Assignment and Security Agreement (Dearborn Interests) dated as of the date
hereof executed by DIHC Dearborn Venture in favor of Administrative Agent;
instrument or agreement securing or otherwise evidencing the obligations in
respect of the Guaranty, including UCC financing statements.

            "Default" means any event or condition which constitutes an Event of
Default or which upon notice, lapse of time or both would, unless cured or
waived, become an Event of Default.

            "Default Rate" shall have the meaning set forth in Section 2.2(c) of
this Agreement.
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                                      4

            "Dollars" or "$" refers to lawful money of the United States of
America.

            "Environmental Laws" shall mean (1) the Comprehensive Environmental
Response, Compensation and Liability Act of 1980, as amended by the Superfund
Amendments and Reauthorization Act of 1986, 42 U.S.C.A. Section 9601 ("CERCLA"),
(2) the Resource Conservation and Recovery Act, as amended by the Hazardous and
Solid Waste Amendment of 1984, 42 U.S.C.A. Section 6901, (3) the Clean Air Act,
42 U.S.C.A. Section 7401, (4) the Federal Water Pollution Control Act of 1977,
33 U.S.C.A. Section 1251, (5) the Toxic Substances Control Act, 15 U.S.C.A.
2601, (6) all other laws, rules, regulations and ordinances relating to air
pollution, water pollution, and/or the handling, discharge, existence, disposal
or recovery of on-site or off-site hazardous, toxic waste, substances or
materials, as each of the foregoing may be amended from time to time, and (7)
the rules, regulations, and ordinances, court or administrative order of decree
or private agreement or interpretation relating to the use, manufacture,
distribution, labeling, handling, collection, storage, treatment or disposal of
any Hazardous Materials of (A) the city, county and state in which Borrower has
disposed of Hazardous Materials, (B) the Environmental Protection Agency and (C)
all other applicable federal, state, regional and local agencies and bureaus,
whether now or hereafter in existence.

            "ERISA" shall mean the Employee Retirement Income Security Act of
1974, as amended from time to time, or any successor statute, and the
regulations promulgated and the rulings issued thereunder.

            "Event of Default" has the meaning assigned to it in Article VI of
this Agreement.

            "Exchange Act" means the Securities Exchange Act of 1934, as
amended.

            "Excluded Taxes" means, with respect to the Administrative Agent,
any Lender or any other recipient of any payment to be made by or on account of
any obligation of the Borrower or any Guarantor hereunder, (a) income or
franchise taxes imposed on (or measured by) its net income by the United States
of America, or by the jurisdiction under the laws of which such recipient is
organized or in which its principal office is located or, in the case of any
Lender, in which its applicable lending office is located, (b) any branch
profits taxes imposed by the United States of America or any similar tax imposed
by any other jurisdiction in which the Borrower or any Guarantor is located and
(c) in the case of a Foreign Lender, any withholding tax that is imposed on
amounts payable to such Foreign Lender at the time such Foreign Lender becomes a
party to this Agreement or is attributable to such Foreign Lender's failure or
inability to comply with Section 2.6(e), except to the extent that such Foreign
Lender's assignor (if any) was entitled, at the time of assignment, to receive
additional amounts from the Borrower or any Guarantor with respect to such
withholding tax pursuant to Section 2.6(a).

            "Financial Officer" means the chief financial officer, principal
accounting officer, treasurer or controller of the Borrower.
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                                      5

            "Financial Statements" has the meaning ascribed to it in Section 4.1
of this Agreement.

            "Foreign Lender" means any Lender that is organized under the laws
of the jurisdiction other than that in which the Borrower is located. For
purposes of this definition, the United States of America, each State thereof
and the District of Columbia shall be deemed to constitute a single
jurisdiction.

            "GAAP" shall mean generally accepted accounting principles in the
United States of America, consistently applied, that are in effect from time to
time.

            "Governmental Authority" means the government of the United States
of America, any political subdivision thereof, whether state or local, and any
agency, authority, instrumentality, regulatory body, court, central bank or
other entity exercising executive, legislative, judicial, taxing, regulatory or
administrative powers or functions of or pertaining to the government of the
United States of America or any political subdivision thereof.

            "Guarantee" of or by any Person (the "guarantor") means any
obligation, contingent or otherwise, of the guarantor guaranteeing or having the
economic effect of guaranteeing any Indebtedness or other obligation of any
other Person (the "primary borrower") in any manner, whether directly or
indirectly, and including any obligation of the guarantor, direct or indirect,
(a) to purchase or pay (or advance or supply funds for the purchase or payment
of) such Indebtedness or other obligation or to purchase (or to advance or
supply funds for the purchase of) any security for the payment thereof, (b) to
purchase or lease property, securities or services for the purpose of assuring
the owner or such Indebtedness or other obligation of the payment thereof, (c)
to maintain working capital, equity capital or any other financial statement,
condition or liquidity of the primary borrower so as to enable the primary
borrower to pay such Indebtedness or other obligation or (d) as an account party
in respect of any letter of credit or letter of guaranty issued to support such
Indebtedness or obligation; provided, that the term Guarantee shall not include
endorsements for collection or deposit in the ordinary course of business.

            "Guaranty" means, collectively and, as amended, supplemented or
modified from time to time, (i) that certain Guaranty dated as of the date
hereof executed by certain of the Guarantors in favor of Administrative Agent
for the benefit of the Lenders (the "Recourse Guaranty"), (ii) that certain
Non-Recourse Guaranty dated as of the date hereof executed by certain of the
Guarantors in favor of Administrative Agent for the benefit of the Lenders and
(iii) that certain Guaranty dated as of the date hereof executed by Cornerstone
Properties Inc. in favor of the Administrative Agent for the benefit of the
Lenders (the "Cornerstone Guaranty").
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                                      6

            "Guarantor" means, collectively, the Note A Guarantors, the Note B
Guarantors, the Note C Guarantors, the Note D Guarantors and the Note E
Guarantors. The term Guarantor shall also include Madison Avenue in its capacity
as the issuer of Note D.

            "Hazardous Materials" means any hazardous substance, toxic substance
or hazardous waste, the generation, handling, storage, treatment or disposal of
which is regulated by any local or state Governmental Authority in any
jurisdiction in which Borrower has owned, leased or operated real estate or
disposed of hazardous materials, or by the United States Government, including
any material or substance which is (1) defined as a "hazardous waste,"
"hazardous substance," "extremely hazardous waste," or "restricted hazardous
waste" or other similar term or phrase under any such law, (2) petroleum,
radioactive materials, asbestos, radon and lead contaminated materials, (3)
designated as a "hazardous substance" pursuant to Section 311 of the Federal
Water Pollution Control Act, 33 U.S.C.A. 1251 (33 U.S.C.A. 1321), (4) designated
as a toxic substance pursuant to the Toxic Substances Control Act, 15 U.S.C.A.
2601, (5) listed pursuant to Section 307 of the Federal Water Pollution Control
Act (33 U.S.C.A. 1317), (6) de fined as a "hazardous waste" pursuant to Section
1004 of the Resource Conservation and Recovery Act, 42 U.S.C.A. 6901 (42
U.S.C.A. 6903), or (7) defined as a "hazardous substance" pursuant to Section
101 of the Comprehensive Environmental Response, Compensation, and Liability
Act, 42 U.S.C.A. 9601 (42 U.S.C.A. 9601).

            "Indebtedness" of any Person means, without duplication, (a) all
obligations of such Person for borrowed money or with respect to deposits or
advances of any kind, (b) all obligations of such Person evidenced by bonds,
debentures, notes or similar instruments, (c) all obligations of such Person
upon which interest charges are customarily paid, (d) all obligations of such
Person under conditional sale or other title retention agreements relating to
property acquired by such Person, (e) all obligations of such Person in respect
of the deferred purchase price of property or services (excluding current
accounts payable incurred in the ordinary course of business), (f) all
Indebtedness of others secured by (or for which the holder of such Indebtedness
has an existing right, contingent or otherwise, to be secured by) any Lien on
property owned or acquired by such Person, whether or not the Indebtedness
secured thereby has been assumed, (g) all Guarantees by such Person of
Indebtedness of others, (h) all Capital Lease Obligations of such Person, (i)
all obligations, contingent or otherwise, of such Person as an account party in
respect of letters of credit and letters of guaranty and (j) all obligations,
contingent or otherwise, of such Person in respect of bankers' acceptances. The
Indebtedness of any Person shall include the Indebtedness of any other entity
(including any partnership in which such Person is a general partner) to the
extent such Person is liable therefor as a result of such person's ownership
interest in or other relationship with such entity, except to the extent the
terms of such Indebtedness provide that such Person is not liable therefor.

            "Indemnified Taxes" means Taxes other than Excluded Taxes.
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                                      7

            "Lenders" means the holders of the Notes listed on Schedule 1.1 and
any other Person that shall have become a party hereto pursuant to an Assignment
and Acceptance, other than any such Person that ceases to be a party hereto
pursuant to an Assignment and Acceptance.

            "Lien" means any interest in property securing an obligation owed
to, or a claim by, a Person other than the owner of the property, whether such
interest is based on the common law, statute or contract, and including but not
limited to the security interest lien arising from a mortgage, encumbrance,
charge, pledge, conditional sale or trust receipt or a lease, consignment or
bailment for security purposes. The term "Lien" shall include, with respect to
stock, stockholder agreements, voting trust agreements, buy-back agreements and
all similar arrangements affecting property. For the purposes of this Agreement,
Borrower or a Guarantor shall be deemed to be the owner of any property which it
has acquired or holds subject to a conditional sale agreement, capitalized lease
or other arrangement pursuant to which title to the property has been retained
by or vested in some other Person for security purposes and such retention or
vesting shall constitute a Lien.

            "Loan" means the loan made by the Lenders to the Borrower and
CStone-527 Madison, Inc. pursuant to this Agreement in the aggregate principal
amount of $250,000,000.

            "Loan Documents" means this Agreement, the Notes, the Guaranty and
the Collateral Agreements.

            "Madison Avenue" means CStone-527 Madison, Inc., a Delaware
corporation.

            "Madison Security Documents" shall mean that certain Amended and
Restated Mortgage and Security Agreement dated as of the date hereof executed by
Madison Avenue in favor of Administrative Agent, that certain Assignment of
Lessor's Interest in Leases dated as of the date hereof executed by Madison
Avenue in favor of Administrative Agent, that certain Environmental
Indemnification Agreement dated as of the date hereof executed by Madison Avenue
in favor of Administrative Agent, that certain Stock Pledge Agreement
(CStone-527 Madison Inc.) dated as of the date hereof (the "Additional New York
Mortgage") executed by Borrower in favor of Administrative Agent, that certain
Mortgage and Security Agreement dated as of the date hereof executed by Madison
Avenue in favor of Administrative Agent and any other document, instrument or
agreement securing or otherwise evidencing the obligations in respect of Note D
including UCC financing statements.

            "Maturity Date" shall mean (a) October __, 2000 with respect to Note
A and Note B; (b) October __, 2004 with respect to Note C and Note D, and (c)
October __, 2007 with respect to Note E.

            "Note A" means that certain Deferred Purchase Price Note (Note A)
dated as of the date hereof and executed by the Borrower in the original
principal amount of $55,000,000 and
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                                      8

any replacements or substitutions therefor, each as amended, supplemented or
modified from time to time.

            "Note B" means that certain Deferred Purchase Price Note (Note B)
dated as of the date hereof and executed by the Borrower in the original
principal amount of $10,000,000 and any replacements or substitutions therefor,
each as amended, supplemented or modified from time to time.

            "Note C" means that certain Deferred Purchase Price Note (Note C)
dated as of the date hereof and executed by the Borrower in the original
principal amount of $30,000,000 and any replacements or substitutions therefor,
each as amended, supplemented or modified from time to time.

            "Note D" means that certain Deferred Purchase Price Note (Note D)
dated as of the date hereof and executed by Madison Avenue in the original
principal amount of $35,000,000 and any replacements or substitutions therefor,
each as amended, supplemented or modified from time to time.

            "Note E" means that certain Deferred Purchase Price Note (Note E)
dated as of the date hereof and executed by the Borrower in the original
principal amount of $120,000,000 and any replacements or substitutions therefor,
each as amended, supplemented or modified from time to time.

            "Note A Collateral Agreements" means the Bryce Security Documents
and the Charlotte Office Security Documents.

            "Note B Collateral Agreements" means the Dearborn Security
Documents.

            "Note C Collateral Agreements" means the Oakbrook Security
Documents.

            "Note D Collateral Agreements" means the Madison Security Documents.

            "Note E Collateral Agreements" means the Properties Security
Documents and the Collateral Note Documents.

            "Note A Guarantors" means, collectively, Charlotte Office Tower
Associates, Charlotte Plaza Properties, Inc., Balsam Mountain, Inc. and Bryce
Mountain, Inc.

            "Note B Guarantors" means, collectively, Dearborn Interests, DIHC
Dearborn Venture, DIHC Marble Place Properties, Inc. and DIHC Dearborn
Properties, Inc.

            "Note C Guarantor" means, CStone-Oakbrook, Inc.
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                                      9

            "Note D Guarantors" means CStone-527 Madison, Inc.

            "Note E Guarantors" means, collectively, DIHC of Georgia, Inc. and
DIHC Properties I, Inc.

            "Notes" means, collectively, Note A, Note B, Note C, Note D and Note
E.

            "Oakbrook Security Documents" shall mean that certain Deed of Trust
and Security Agreement dated as of the date hereof executed by CStone-Oakbrook,
Inc. in favor of Administrative Agent, that certain Assignment of Lessor's
Interest in Leases dated as of the date hereof executed by CStone-Oakbrook, Inc.
in favor of Administrative Agent, that certain Environmental Indemnification
Agreement dated as of the date hereof executed by CStone-Oakbrook, Inc. in favor
of Administrative Agent and that certain Stock Pledge Agreement
(CStone-Oakbrook, Inc.) dated as of the dated hereof executed by Borrower in
favor of Administrative Agent and any other document, instrument or agreement
securing or otherwise evidencing the obligations in respect of the Guaranty,
including UCC financing statements.

            "Other Taxes" means any and all present or future stamp or
documentary Taxes or any other excise or property Taxes arising from any payment
made hereunder or from the execution, delivery, or enforcement of, or otherwise
with respect to, this Agreement.

            "Person" means any natural person, corporation, limited liability
company, trust, joint venture, association, company, partnership, Governmental
Authority or other entity.

            "Prime Rate" means the rate of interest per annum publicly announced
from time to time by The Chase Manhattan Bank as its prime rate in effect at its
principal office in New York City; each change in the Prime Rate shall be
effective from and including the date such change is publicly announced as being
effective.

            "Properties Security Documents" shall mean that certain Deed to
Secure Debt and Security Agreement dated as of the date hereof executed by DIHC
Properties I, Inc. in favor of Administrative Agent, that certain Assignment of
Lessor's Interest in Leases dated as of the date hereof executed by DIHC
Properties I, Inc. in favor of Administrative Agent, that certain Environmental
Indemnification Agreement dated as of the date hereof executed by DIHC
Properties I, Inc. in favor of Administrative Agent and that certain Stock
Pledge Agreement (DIHC Properties I, Inc.) dated as of the dated hereof executed
by DIHC of Georgia, Inc. in favor of Administrative Agent and any other
document, instrument or agreement securing or otherwise evidencing the
obligations in respect of the Guaranty, including UCC financing statements.

            "Register" has the meaning set forth in Section 8.5.
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                                      10

            "Related Parties" means, with respect to any specified Person, such
Person's Affiliates and the respective directors, officers, employees, agents
and advisors of such Person and such Person's Affiliates.

            "Required Filing Date" has the meaning ascribed to it in Section 4.1
of this Agreement.

            "Required Lenders" shall mean Lenders holding a majority in
outstanding principal amount of Note A, plus Lenders holding a majority in
outstanding principal amount of Note B, plus a Lenders holding a majority in
principal amount of Note C, plus Lenders holding a majority in principal amount
of Note D, plus Lenders holding a majority in outstanding principal amount of
Note E. For purposes of calculating Required Lenders, the principal amount of
any portion of the Notes held by Borrower or any Affiliate of Borrower shall be
excluded in determining whether Lenders holding a majority of the outstanding
principal amount of that Note consent to an action; provided, however, in the
event that Borrower or an Affiliate of Borrower owns 100% of a Note (for
example, where Borrower is the holder of the full principal amount of Note A),
the foregoing provision shall be inapplicable with respect to a determination as
to whether the holders of that Note consent to an action.

            "Securities" has the meaning set forth in Section 2(1) of the
Securities Act of 1933, as amended.

            "Subsidiary" means, with respect to any Person (the "parent") at any
date, any corporation, limited liability company, partnership, association or
other entity the accounts of which would be consolidated with those of the
parent in the parent's consolidated financial statements if such financial
statements were prepared in accordance with GAAP as of such date, as well as any
other corporation, limited liability company, partnership, association or other
entity (a) of which securities or other ownership interests representing more
than 50% of the equity or more than 50% of the ordinary voting power or, in the
case of a partnership, more than 50% of the general partnership interests are,
as of such date, owned, controlled or held, or (b) that is, as of such date,
otherwise Controlled, by the parent or one or more subsidiaries of the parent or
by the parent and one or more subsidiaries of the parent.

            "Taxes" means any and all present or future taxes, levies, imposts,
duties, deductions, charges or withholdings imposed by any Governmental
Authority.

            "Transactions" means the execution, delivery and performance by the
Borrower and the Guarantors of this Agreement and the other Loan Documents, the
borrowing of Loans, and the use of the proceeds thereof.

            SECTION 1.2 Terms Generally. The definitions of terms herein shall
apply equally to the singular and plural forms of the terms defined. Whenever
the context may require,
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                                      11

any pronoun shall include the corresponding masculine, feminine and neuter
forms. The words "include", "includes" and including" shall be deemed to be
followed by the phrase "without limitation." The word "will" shall be construed
to have the same meaning and effect as the word "shall." Unless the context
requires otherwise (a) any definition of or reference to any agreement,
instrument or other document herein shall be construed as referring to such
agreement, instrument or other document as from time to time amended,
supplemented or otherwise modified (subject to any restrictions on such
amendments, supplements or modifications set forth herein), (b) any reference
herein to any Person shall be construed to include such Person's successors and
assigns, (c) the words "herein", "hereof" and "hereunder", and words of similar
import, shall be construed to refer to this Agreement in its entirety and not to
any particular provision hereof, (d) all references herein to Articles,
Sections, Exhibits and Schedules shall be construed to refer to Articles and
Sections of, and Exhibits and Schedules to, this Agreement and (e) the words
"asset" and "property" shall be construed to have the same meaning and effect
and to refer to any and all tangible and intangible assets and properties,
including cash, securities, accounts and contract rights.

            SECTION 1.3 Accounting Terms; GAAP. Except as otherwise expressly
provided herein, all terms of an accounting or financial nature shall be
construed in accordance with GAAP, as in effect from time to time; provided
that, if the Borrower notifies the Administrative Agent that the Borrower
requests an amendment to any provision hereof to eliminate the effect of any
change occurring after the date hereof in GAAP or in the application thereof on
the operation of such provision (or if the Administrative Agent notifies the
Borrower that the Required Lenders request an amendment to any provision hereof
for such purpose), regardless of whether any such notice is given before or
after such change in GAAP or in the application thereof, then such provision
shall be interpreted on the basis of GAAP as in effect and applied immediately
before such change shall have become effective until such notice shall have been
withdrawn or such provision amended in accordance herewith.


                                 ARTICLE  II.

                                   The Loan

            SECTION 2.1 Loan. Upon the terms and subject to the conditions
hereof and the other Loan Documents, Lenders agree to make the Loan to Borrower
and Madison Avenue in accordance with this Agreement.

            SECTION 2.2 The Notes. The borrowings hereunder shall be evidenced
by the Notes in the form attached hereto as Schedule 2.2.

            (a) Repayment of Notes. The Borrower and Madison Avenue hereby
unconditionally promise to pay to each Lender directly, in federal funds or
other funds
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                                      12

immediately available, the then unpaid principal amount of each Note issued by
it and held by such Lender on the Maturity Date of such Note to pay all other
sums as when such amounts become due under the terms of such Notes.

            (b) Limitation on Interest. Notwithstanding anything herein to the
contrary, if at any time the interest rate applicable to any Note, together with
all fees, charges and other amounts which are treated as interest on such Note
under applicable law (collectively the "Charges"), shall exceed the maximum
lawful rate (the "Maximum Rate") which may be contracted for, charged, taken,
received or reserved by the Lender holding such Note in accordance with
applicable law, the rate of interest payable in respect of such Note hereunder,
together with all Charges payable in respect thereof, shall be limited to the
Maximum Rate and, to the extent lawful, the interest and Charges that would have
been payable in respect of such Note but were not payable as a result of the
operation of this Section shall be cumulated and the interest and Charges
payable to such Lender in respect of other Notes or periods shall be increased
(but not above the Maximum Rate therefor) until such cumulated amount, together
with interest thereon at the Federal Funds Effective Rate to the date of
repayment, shall have been received by such Lender.

            (c) Late Charges; Default Rate. In the event any payment due under
the Notes is not paid within five (5) business days following the due date for
such payment, Borrower, or Madison Avenue in the case of Note D, shall pay to
the holder of such Note a late charge for the month during which such payment is
not made when due, and for each month or fraction thereof that such sum remains
unpaid, equal to five percent (5%) of such payment. In addition, in the event
Borrower, or Madison Avenue in the case of Note D, fails to pay any installment
of principal and interest on the date due, the unpaid amount shall accrue
interest at the Default Rate until paid. "Default Rate" shall be the higher of
(a) 3% above the nondefault interest rate set forth in each Note or (b) 3% above
the Prime Rate.

            (d) Prepayment. The indebtedness evidenced by any Note (or any
portion of a Note) may not be prepaid, either in whole or in part, without the
express written consent of the Lender holding that Note; provided, however, the
Borrower or Madison Avenue in the case of Note D may prepay the indebtedness
evidenced by any Note without penalty on or after the date which is sixty (60)
days prior to the Maturity Date of such Note.

            SECTION 2.3 The Guaranty. The indebtedness evidenced by the Notes
shall be guaranteed by each Guarantor pursuant to the terms of the Guaranty in
the forms attached hereto as Schedule 2.3. In addition, Borrower shall guarantee
the indebtedness evidenced by Note D pursuant to the terms of the Cornerstone
Guaranty in the form attached hereto as Schedule 2.3A. Borrower shall, and shall
cause each Guarantor to, execute and deliver the Guaranty to the Administrative
Agent and to abide by and to fully perform the obligations contained therein.
<PAGE>

                                      13

            SECTION 2.4 The Collateral Agreements. (a) The indebtedness and
obligations evidenced by the Guaranty and the Notes shall be secured by the
Collateral Agreements. Borrower shall cause Charlotte Office Tower Associates,
Balsam Mountain, Inc. and Charlotte Plaza Properties, Inc. to execute and
deliver the Charlotte Office Security Documents and to abide by and to perform
fully the obligations contained therein. Borrower shall cause Bryce Mountain to
execute and deliver the Bryce Security Documents and to abide by and to perform
fully the obligations contained therein. Borrower shall cause DIHC Properties I,
Inc. and DIHC of Georgia, Inc. to execute and deliver the Properties Security
Documents and to abide by and to perform fully the obligations contained
therein. Borrower shall cause DIHC Dearborn Venture, Dearborn Interests, DIHC
Marble Place Properties, Inc. and DIHC Dearborn Properties, Inc. to execute and
deliver the Dearborn Security Documents and to abide by and perform fully the
obligations contained therein. Borrower shall cause CStone-Oakbrook, Inc. to
execute and deliver the Oakbrook Security Documents and to abide by and to
perform fully the obligations contained therein. Borrower shall cause CStone-527
Madison, Inc. to execute and deliver the Madison Security Documents and to abide
by and to perform fully the obligations contained therein. Borrower shall
execute and deliver the Collateral Note Documents and shall abide by and perform
fully the obligations contained therein.

            (b) The Borrower and Madison Avenue acknowledge that Administrative
Agent is holding an original, fully executed and acknowledged counterpart of the
Additional New York Mortgage, which Additional New York Mortgage is not intended
to be recorded at the time of the closing of the Transactions. The Borrower and
Madison Avenue acknowledge and agree that Administrative Agent has the right, in
its sole and absolute discretion, at any time from and after the date hereof to
record and file the Additional New York Mortgage. The Lenders shall, ratably in
accordance with the aggregate outstanding principal amount of their respective
Notes, pay (or shall reimburse the Administrative Agent for) all costs and
expenses (including payment of all applicable mortgage recording taxes, filing
and recording charges and title charges and premiums relating thereto (the
"Additional New York Mortgage Charges")) and neither Borrower nor Madison Avenue
nor any other Guarantor shall be obligated or liable under any provision of the
Loan Documents for the payment of the New York Mortgage Charges; provided,
however, Madison Avenue agrees that it will be solely responsible for the
payment of, and shall pay or reimburse the Administrative Agent and the Lenders
for the payment of, any and all Additional New York Mortgage Charges incurred
after the continuance of an Event of Default.

            SECTION 2.5 Termination of Guaranty and Collateral Agreements.
Notwithstanding anything to the contrary contained herein, any and all liability
or obligation of the Note A Guarantors under the Guaranty as well as the Note A
Collateral Agreements shall terminate and be discharged in full upon payment and
performance, in full, of Note A, provided, however, no Default or Event of
Default shall have occurred and be continuing at the time of such termination
and discharge, unless such Event of Default will be cured, or cease to exist, as
a result of such termination or discharge; any and all liability or obligation
of Note B Guarantors under the Guaranty as well as the Note B Collateral
Agreements shall terminate and be discharged in full
<PAGE>

                                      14

upon payment and performance, in full, of Note B, provided, however, no Default
or Event of Default shall have occurred and be continuing at the time of such
termination and discharge, unless such Event of Default will be cured, or cease
to exist, as a result of such termination or discharge; and any and all
liability or obligation of the Note C Guarantors under the Guaranty as well as
the Note C Collateral Agreements shall terminate and be discharged in full upon
payment and performance, in full, of Note C, provided, however, no Default or
Event of Default shall have occurred and be continuing at the time of such
termination and discharge, unless such Event of Default will be cured, or cease
to exist, as a result of such termination or discharge; any and all liability or
obligation of the Note D Guarantors or Borrower under the Guaranty as well as
the Note D Collateral Agreements shall terminate and be discharged in full upon
payment and performance, in full, of Note D, provided, however, no Default or
Event of Default shall have occurred and be continuing at the time of such
termination and discharge, unless such Event of Default will be cured, or cease
to exist, as a result of such termination or discharge; and any and all
liability or obligation of the Note E Guarantors under the Guaranty as well as
the Note E Collateral Agreements shall terminate and be discharged in full upon
payment and performance, in full, of Note E, provided, however, no Default or
Event of Default shall have occurred and be continuing at the time of such
termination and discharge, unless such Event of Default will be cured or cease
to exist, as a result of such termination or discharge.

            SECTION  2.6  Taxes.

            (a) Any and all payments by or on account of any obligation of the
Borrower, Madison Avenue or any Guarantor under any Loan Document shall be made
free and clear of and without deduction for any Indemnified Taxes or Other
Taxes; provided that if the Borrower or any Guarantor shall be required to
deduct any Indemnified Taxes or Other Taxes from such payments, then (i) the sum
payable shall be increased as necessary so that after making all required
deductions (including deductions applicable to additional sums payable under
this Section) the Lender receives an amount equal to the sum it would have
received had no such deductions been made, (ii) the Borrower or any Guarantor
shall make such deductions and (iii) the Borrower or any Guarantor shall pay the
full amount deducted to the relevant Governmental Authority in accordance with
applicable law.

            (b) In addition, the Borrower or any Guarantor shall pay any Other
Taxes to the relevant Governmental Authority in accordance with applicable law.

            (c) The Borrower or any Guarantor shall indemnify each Lender within
10 days after written demand therefor, for the full amount of any Indemnified
Taxes or Other Taxes (including Indemnified Taxes or Other Taxes imposed or
asserted on or attributable to amounts payable under this Section) paid by such
Lender and any penalties, interest and reasonable expenses arising therefrom or
with respect thereto, whether or not such Indemnified Taxes or Other Taxes were
correctly or legally imposed or asserted by the relevant Governmental
<PAGE>

                                      15

Authority. A certificate as to the amount of such payment or liability delivered
to the Borrower or any Guarantor by a Lender shall be conclusive absent manifest
error.

            (d) As soon as practicable after any payment of Indemnified Taxes or
Other Taxes by the Borrower or any Guarantor to a Governmental Authority, the
Borrower or any Guarantor shall deliver to the Lender the original or a
certified copy of a receipt issued by such Governmental Authority evidencing
such payment, a copy of the return reporting such payment or other evidence of
such payment reasonably satisfactory to the Lender.

            (e) Any Foreign Lender that is entitled to an exemption from or
reduction of withholding tax under the law of the jurisdiction in which the
Borrower or any Guarantor is located, or any treaty to which such jurisdiction
is a party, with respect to payments under this Agreement shall deliver to the
Borrower, at the time or times prescribed by applicable law or reasonably
requested by the Borrower or any Guarantor, such properly completed and executed
documentation prescribed by applicable law as will permit such payments to be
made without withholding or at a reduced rate.

            (f) Each Lender and the Administrative Agent shall reasonably
cooperate with Borrower or any Guarantor (at the cost and expense of the
Borrower) in challenging or contesting the imposition of any Tax which Borrower
or Guarantor reasonably believes is not due.

            SECTION  2.7  Payments Generally; Pro Rata Treatment; Sharing of
Set-offs.

            (a) The Borrower and Madison Avenue shall make each payment required
to be made by it hereunder or any Note (whether of principal, interest, or
otherwise) prior to 12:00 noon, New York City time, on the date when due, in
immediately available funds, without set-off, deduction or counterclaim. Any
amounts received after such time on any date may, in the discretion of the
Lender, be deemed to have been received on the next succeeding Business Day for
purposes of calculating interest thereon. All such payments shall be made
directly to each Lender at its address specified in Schedule 1.1 hereto or at
such other address as may be designated by such Lender from time to time by
written notice at least five (5) Business Days prior to any payment date. The
Administrative Agent shall distribute any such payments received by it for the
account of any other Person to the appropriate recipient promptly following
receipt thereof. If any payment hereunder shall be due on a day that is not a
Business Day, the date for payment shall be extended to the next succeeding
Business Day, and, in the case of any payment accruing interest, interest
thereon shall be payable for the period of such extension. All payments
hereunder shall be made in Dollars.

            (b) (i) If any Lender or the Administrative Agent obtains any
proceeds of the Collateral which is the subject of the Note A Collateral
Agreements and which either the Administrative Agent or any Lender is entitled
to apply to the Indebtedness evidenced by the
<PAGE>

                                      16

Notes, then such proceeds shall be applied first, to pay any costs or fees of
the Administrative Agent in obtaining or realizing such proceeds, second, to
reduce any costs or fees then due under Note A, applied ratably among the
holders of Note A in accordance with the amounts of costs and fees then due to
such holders, third, to pay accrued and unpaid interest due under Note A,
applied ratably among the holders of Note A in accordance with the amounts of
interest then due to such holders, and fourth, to pay principal then due under
Note A, applied ratably among the holders of Note A in accordance with the
amounts of principal then due to such holders.

            (ii) If any Lender or the Administrative Agent obtains any proceeds
of the Collateral which is the subject of the Note B Collateral Agreements and
which either the Administrative Agent or any Lender is entitled to apply to the
indebtedness evidenced by the Notes, then such proceeds shall be applied first,
to pay any costs or fees of the Administrative Agent in obtaining and realizing
on any such proceeds, second, to reduce any costs or fees then due under Note B,
applied ratably among the holders of Note B in accordance with the amounts of
costs and fees then due to such holders, third, to pay accrued and unpaid
interest due under Note B, applied ratably among the holders of Note B in
accordance with the amounts of interest then due to such holders, and fourth, to
pay principal then due under Note B, applied ratably among the holders of Note B
in accordance with the amounts of principal then due to such holders.

            (iii) If any Lender or the Administrative Agent obtains any proceeds
of the Collateral which is the subject of the Note C Collateral Agreements and
which either the Administrative Agent or any Lender is entitled to apply to the
indebtedness evidenced by the Notes, then such proceeds shall be applied first,
to pay any costs or fees of the Administrative Agent in obtaining and realizing
on any such proceeds, second, to reduce any costs or fees then due under Note C,
applied ratably among the holders of Note C in accordance with the amounts of
costs and fees then due to such holders, third, to pay accrued and unpaid
interest due under Note A, applied ratably among the holders of Note C in
accordance with the amounts of interest then due to such holders, and fourth, to
pay principal then due under Note C, applied ratably among the holders of Note C
in accordance with the amounts of principal then due to such holders.

            (iv) If any Lender or the Administrative Agent obtains any proceeds
of the Collateral which is the subject of the Note D Collateral Agreements and
which either the Administrative Agent or any Lender is entitled to apply to the
indebtedness evidenced by the Notes, then such proceeds shall be applied first,
to pay any costs or fees of the Administrative Agent in obtaining and realizing
on any such proceeds, second, to reduce any costs or fees then due under Note D,
applied ratably among the holders of Note D in accordance with the amounts of
costs and fees then due to such holders, third, to pay accrued and unpaid
interest due under Note D, applied ratably among the holders of Note D in
accordance with the amounts of interest then due to such holders, and fourth, to
pay principal then due under Note D, applied ratably
<PAGE>

                                      17

among the holders of Note D in accordance with the amounts of principal then due
to such holders.

            (v) If any Lender or the Administrative Agent obtains any proceeds
of the Collateral which is the subject of the Note E Collateral Agreements and
which either the Administrative Agent or any Lender is entitled to apply to the
indebtedness evidenced by the Notes, then such proceeds shall be applied first,
to pay any costs or fees of the Administrative Agent in obtaining and realizing
on any such proceeds, second, to reduce any costs or fees then due under Note E,
applied ratably among the holders of Note E in accordance with the amounts of
costs and fees then due to such holders, third, to pay accrued and unpaid
interest due under Note E, applied ratably among the holders of Note E in
accordance with the amounts of interest then due to such holders, and fourth, to
pay principal then due under Note E, applied ratably among the holders of Note E
in accordance with the amounts of principal then due to such holders.

            (vi) After application in accordance with the preceding paragraphs
of this Section 2.7(b), to the extent any proceeds remain, then such proceeds
shall be applied first to the Administrative Agent to pay any costs or fees then
due, second to reduce any costs or fees then due under the Notes, applied
ratably among the holders of the Notes in accordance with the amount of costs
and fees then due to such holders, third to pay accrued and unpaid interest due
under the Notes, applied ratably among the holders of the Notes in accordance
with the amount of interest then due to such holders and fourth, to pay
principal then due under the Notes, applied ratably among the holders of the
Notes in accordance with the amount of principal then due to such holders.

            (vii) After application in accordance with the preceding paragraphs
of this Section 2.7(b), to the extent any proceeds remain, then such proceeds
shall be delivered as the owner of such property shall direct (including to any
creditor or such owner as directed under any agreement by such owner).

            (c) If at any time insufficient funds are received by and available
to the Administrative Agent to pay fully all amounts of principal, interest and
fees then due under the Notes, such funds shall be applied (i) first, to pay
interest and fees then due under the Notes, ratably among the parties entitled
thereto in accordance with the amounts of interest and fees then due to such
parties, and (ii) second, to pay principal then due under the Notes, ratably
among the parties entitled thereto in accordance with the amounts of principal
under the Notes then due to such parties.

            (d) If any Lender shall, by exercising any right of set-off or
counterclaim or otherwise, obtain payment in respect of any principal of or
interest on any of the Notes resulting in such Lender receiving payment of a
greater proportion of the aggregate amount of the Notes held by such Lender and
accrued interest thereon than the proportion received by any other
<PAGE>

                                      18

Lender, then the Lender receiving such greater proportion shall purchase (for
cash at face value) participation in the Notes of other Lenders to the extent
necessary so that the benefit of all such payments shall be shared by the
Lenders ratably in accordance with the aggregate amount of principal of and
accrued interest on their respective Notes; provided that (i) if any such
participation is purchased and all or any portion of the payment giving rise
thereto is recovered, such participation shall be rescinded and the purchase
price restored to the extent of such recovery, without interest, and (ii) the
provisions of this paragraph shall not be construed to apply to any payment made
by the Borrower or any Guarantor pursuant to and in accordance with the express
terms of this Agreement or any payment obtained by a Lender as consideration for
the assignment of or sale of a participation in any of its Notes to any assignee
or participant, other than to the Borrower or any Subsidiary or Affiliate
thereof (as to which the provisions of this paragraph shall apply). The Borrower
and each Guarantor consents to the foregoing and agrees, to the extent it may
effectively do so under applicable law, that any Lender acquiring a
participation pursuant to the foregoing arrangement may exercise against the
Borrower or any Guarantor rights of set-off and counterclaim with respect to
such participation as fully as if such Lender were a direct creditor of the
Borrower or any Guarantor in the amount of such participation.


                                ARTICLE  III.

                        Representations and Warranties

            The Borrower and each Guarantor represent and warrant to the
Administrative Agent and the Lenders that:

            SECTION 3.1 Organization; Powers. Each of the Borrower and the
Guarantors is duly organized, validly existing and in good standing under the
laws of the jurisdiction of its organization, has all requisite power and
authority to carry on its business as now conducted and, is qualified to do
business in, and is in good standing in, every jurisdiction where such
qualification is required.

            SECTION 3.2 Authorization; Enforceability. The Transactions are
within the Borrower's and each Guarantor's corporate powers and have been duly
authorized by all necessary action (including those by partners and
shareholders). This Agreement has been duly executed and delivered by the
Borrower and constitutes a legal, valid and binding obligation of the Borrower,
enforceable in accordance with its terms, subject to applicable bankruptcy,
insolvency, reorganization, moratorium or other laws affecting creditors' rights
generally and subject to general principles of equity, regardless of whether
considered in a proceeding in equity or at law.
<PAGE>

                                      19

            SECTION 3.3 Governmental Approvals; No Conflicts. The Transactions
(a) do not require any consent or approval of, registration or filing with, or
any other action by, any Governmental Authority, except such as have been
obtained or made and are in full force and effect, (b) will not violate any
applicable law or regulation or the charter, by-laws or other organizational
documents of the Borrower or any of the Guarantors or any order of any
Governmental Authority, and (c) will not violate or result in a default under
any indenture, agreement or other instrument binding upon the Borrower or any of
the Guarantors or its assets, or give rise to a right thereunder to require any
payment to be made by the Borrower or any of the Guarantors.

            SECTION 3.4 Litigation. There are no actions, suits or proceedings
pending or, to the best of Borrower's and each Guarantor's knowledge, threatened
against Borrower or any Guarantor, or involving the Collateral, at law or in
equity, or before any governmental or administrative agency, except actions,
suits and proceedings which are fully covered by insurance or which, if
adversely determined, would not impair the ability of Borrower or any Guarantor
to perform its obligations under and by virtue of the Loan Documents.

            SECTION 3.5 Default. Except as set forth on Schedule 3.5, neither
the Borrower nor any Guarantor is in default under or with respect to any
obligation in any respect which default or defaults would be reasonably expected
in the aggregate to impair the ability of Borrower or any Guarantor to perform
its obligations under and by virtue of the Loan Documents.


                                 ARTICLE  IV.

                             Affirmative Covenants

            Until the principal of and interest on each of the Notes and all
amounts under the Loan Documents shall have been paid in full, the Borrower and
each Guarantor covenant and agree with the Administrative Agent and the Lenders
that:

            SECTION 4.1 Provision of Financial Information. Whether or not
Borrower is subject to Section 13 or 15(d) of the Exchange Act, Borrower will,
to the extent permitted under the Exchange Act, file with the Commission the
annual reports, quarterly reports and other documents which Borrower would have
been required to file with the Commission pursuant to such Section 13 or 15(d)
(the "Financial Statements") if Borrower were so subject, such documents to be
filed with the Commission on or prior to the respective dates (the "Required
Filing Dates") by which Borrower would have been required so to file such
documents if Borrower were so subject.
<PAGE>

                                      20

            Borrower will also in any event (x) within 15 days of each Required
Filing Date (i) transmit by mail to Lenders without cost to Lenders, copies of
the annual reports and quarterly reports which Borrower would have been required
to file with the Commission pursuant to Section 13 or 15(d) of the Exchange Act
if Borrower were subject to such Sections, and (y) if filing such documents by
Borrower with the Commission is not required under the Exchange Act, promptly
upon written request and payment of the reasonable cost of duplication and
delivery, supply copies of such documents to Lenders.

            SECTION 4.2 Statement as to Compliance. Borrower shall deliver to
Lenders within 120 days after the end of each fiscal year, a written statement
signed a Financial Officer of Borrower, stating that:

            (a) a review of the activities of Borrower and each Guarantor during
      such year and of its performance under the Loan Documents has been made
      under his or her supervision, and

            (b) to the best of his or her knowledge, based on such review, (i)
      Borrower and each Guarantor has complied with all the conditions and
      covenants imposed on it under the Loan Documents throughout such year, or,
      if there has been a default in the fulfillment of any such condition or
      covenant, specifying each such default known to him or her and the nature
      and status thereof, and (ii) no Default or Event of Default has occurred
      and is continuing, or if such a Default or Event of Default has occurred
      and is continuing, specifying each such event known to him and the nature
      and status thereof.

            SECTION 4.3 Existence. Borrower and each Guarantor will do or cause
to be done all things necessary to preserve and keep in full force and effect
the existence, rights and franchises of the Borrower and each Guarantor;
provided, however, that Borrower and the Guarantors shall not be required to
preserve any right or franchise if the Board of Directors shall determine that
the preservation thereof is no longer desirable in the conduct of the business
of the Borrower and the Guarantors and that the loss thereof is not
disadvantageous in any material respect to the Administrative Agent or the
Lenders. The foregoing shall not prohibit any merger, consolidation, liquidation
or dissolution permitted under Section 5.2.

            SECTION 4.4 Payment of Taxes and Other Claims. Borrower and each
Guarantor will pay or discharge or cause to be paid or discharged, before the
same shall become delinquent, (i) all taxes, assessments and governmental
charges levied or imposed upon it or any Guarantor or upon the income, profits
or property of Borrower or any Guarantor, and (ii) all lawful claims for labor,
materials and supplies which, if unpaid, might by law become a lien upon the
property of Borrower or any Guarantor; provided, however, that Borrower and each
Guarantor shall not be required to pay or discharge or cause to be paid or
discharged any such tax, assessment, charge or claim whose amount, applicability
or validity is being contested in good faith by appropriate proceedings.
<PAGE>

                                      21

            SECTION 4.5 Books and Records; Inspection Rights. The Borrower will,
and will cause each of the Guarantors to, keep proper books of record and
account in which full, true and correct entries are made of all dealings and
transactions in relation to its business and activities. The Borrower will, and
will cause each of the Guarantors, permit any representatives designated by the
Administrative Agent or any Lender, upon reasonably prior notice, to visit and
inspect its properties, to examine and make extracts from its books and records,
and to discuss its affairs, finances and condition with its officers and
independent accountants, all at such reasonable times and as often as reasonably
required.

            SECTION 4.6 Compliance with Laws. Borrower will promptly comply and
will cause each Guarantor to comply promptly with all laws, ordinances or
governmental rules and regulations to which it is subject, including, without
limitation, the Occupational Safety and Health Act of 1970, as amended, ERISA,
the Americans with Disabilities Act of 1990, as amended, and all Environmental
Laws, the violations of which could reasonably be expected to materially and
adversely affect the properties, business, cash flow or financial condition of
Borrower and its Subsidiaries taken as a whole.


                                 ARTICLE  V.

                              Negative Covenants

            Until the principal of and interest on each of the Notes and all
amounts under the Loan Documents shall have been paid in full, the Borrower and
each Guarantor covenants and agrees with the Administrative Agent and the
Lenders that:

            SECTION 5.1 Indebtedness. The Borrower will not permit any Guarantor
under the Recourse Guaranty to create, incur, assume or permit to exist any
Indebtedness, except: (a) Indebtedness under the Loan Documents, (b) unsecured
Indebtedness to the Borrower or any Subsidiary of the Borrower subordinated to
the obligations under the Loan Documents, (c) Indebtedness existing on the date
hereof and extensions, renewals and replacements or any such Indebtedness that
do not increase the outstanding principal amount thereof and (d) unsecured
Indebtedness incurred to finance improvements to or operate the Collateral
(including but not limited to tenant improvements, leasing commissions or leases
with respect to the Collateral).

            SECTION 5.2 Restriction on Fundamental Changes. Borrower will not,
and will not permit any Guarantor to, enter into any merger or consolidation, or
liquidate, wind-up or dissolve (or suffer any liquidation or dissolution), or
convey, lease, sell, transfer or otherwise dispose of, in one transaction or
series of transactions, all or any substantial part of the Collateral unless no
Default or Event of Default shall be continuing at the time thereof or would
result therefrom and either (1) Borrower or one of the Guarantors is the
surviving or continuing entity resulting from such merger or transfer, or (2)
the surviving or continuing entity of such merger or
<PAGE>

                                      22

transfer agrees in writing to assume the obligations and indebtedness evidenced
by the Notes, the Guaranties and the Collateral Agreements subject to the
provisions of Section 8.11 hereof.

            SECTION 5.3 Transactions with Affiliates. The Borrower shall
conduct, and cause each of the Guarantors to conduct, all transactions with any
Affiliate of Borrower or the Guarantors only on terms that are in writing, fair
and reasonable and no less favorable to Borrower or such Guarantor than it would
obtain in a comparative arm's-length transaction with an independent third
Person; provided however, that nothing herein shall restrict or prohibit any
transaction between or among the Borrower and its Subsidiaries not involving any
other Affiliate.

            SECTION 5.4 Single-Purpose Guarantors. Each Guarantor, other than
DIHC of Georgia, Inc., shall engage in no activity or have any business other
than ownership of the Collateral and activities and businesses reasonably
incidental thereto.

            SECTION 5.5 Guarantors. Until the obligations under the Loan
Documents of any Guarantor is fully terminated and discharged pursuant to
Section 2.5, such Guarantor (other than the Borrower and DIHC of Georgia, Inc.)
shall not be a "Guarantor" under that certain Revolving Credit and Guaranty
Agreement among the Borrower, certain subsidiaries of the Borrower, the lenders
signatory thereto, Bankers Trust Company, as Administrative Agent and Chase
Securities, Inc., as Syndication Agent.

            SECTION 5.6 Changes. The Borrower and each Guarantor will not change
(a) the location of its chief executive office or office where it keeps its
books and records or (b) its name, identity or corporate structure, in each
case, unless (x) it shall have given prior written notice thereof to the
Administrative Agent and (y) it shall have taken all necessary action to
maintain the validity, perfection and priority of the Administrative Agent's
Lien with respect to the Collateral.


                                 ARTICLE  VI.

                               Events of Default

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

            SECTION 6.1 Borrower or Madison Avenue in the case of Note D fails
to pay any installment of principal or interest, or any part thereof, payable
hereunder or under any of the Notes, when and as the same shall become due and
payable, and with respect to payments of interest, such failure is not cured
within five (5) days;
<PAGE>

                                      23

            SECTION 6.2 Borrower or any Guarantor fails to pay any other sums
covenanted to be paid by Borrower or any Guarantor hereunder or under any of the
Notes or any Loan Document or any other instrument or document now or hereafter
evidencing or securing the Notes, when and as the same shall become due and
payable, and such failure is not cured within ten (10) days after written notice
thereof from Lenders to Borrower;

            SECTION 6.3 An involuntary proceeding shall be commenced or an
involuntary petition shall be filed seeking (i) liquidation, reorganization or
other relief in respect of the Borrower or any Guarantor or its debts, or of a
substantial part of its assets, under any federal, state or foreign bankruptcy,
insolvency, receivership or similar law now or hereafter in effect or (ii) the
appointment of a receiver, trustee, custodian, sequestrator, conservator or
similar official for the Borrower or any Guarantor or for a substantial part of
its assets, and, in any such case, such proceeding or petition shall continue
undismissed for 60 days or an order or decree approving or ordering any of the
foregoing shall be entered.

            SECTION 6.4 The Borrower or any Guarantor shall (i) voluntarily
commence any proceeding or file any petition seeking liquidation, reorganization
or other relief under any federal, state or foreign bankruptcy, insolvency,
receivership or similar law now or hereafter in effect, (ii) consent to the
institution of, or fail to contest in a timely and appropriate manner, any
proceeding or petition described in Section 6.3 of this Agreement, (iii) apply
for or consent to the appointment of a receiver, trustee, custodian,
sequestrator, conservator or similar official for the Borrower or any Guarantor
or for a substantial part of its assets, (iv) file an answer admitting the
material allegations of a petition filed against it in any such proceeding, (v)
make a general assignment for the benefit of creditors or (vi) take any action
for the purpose of effecting any of the foregoing.

            SECTION 6.5 The Borrower or any Guarantor shall become unable, admit
in writing or fail generally to pay its debts as they become due.

            SECTION 6.6 Any warranty, covenant, representation or statement of
Borrower or Guarantor, or which is or has been made on behalf of Borrower or
Guarantor, in this Agreement, the Notes, the Guaranty or the Collateral
Agreements or in any loan commitment, affidavit, certificate or other instrument
or document now or hereafter evidencing, securing or otherwise relating to the
Indebtedness evidenced by the Notes, or any part thereof, proves untrue or
misleading in any material respect; or Borrower or any Guarantor fails to keep,
observe, perform, carry out and execute in every particular any other covenant,
agreement, obligation or condition contained herein, in any of the Notes, the
Guaranty, the Collateral Agreements or any other instrument or document now or
hereafter evidencing or securing the Indebtedness evidenced by the Notes or any
part thereof, and such untruth, misleading matter, failure or default is not
cured within thirty (30) days after the earlier of the Borrower's or any
Guarantor's knowledge thereof or written notice thereof from the Administrative
Agent or any Lender to Borrower or any Guarantor.
<PAGE>

                                      24

            SECTION 6.7 The Collateral Agreements shall for any reason (other
than pursuant to the terms thereof (except due solely to the act or omission of
the Administrative Agent or the Lenders)) cease to create a valid and perfected
Lien on the Collateral. The Guaranty shall for any reason become invalid or
unenforceable or the Borrower or any Guarantor shall so assert in writing.

            SECTION 6.8 Any "Event of Default" shall occur under any of the
Notes, the Guaranty or the Collateral Agreements.

            SECTION 6.9 Acceleration of Maturity; Recession and Annulment. In
the event of an occurrence and continuation of an Event of Default hereunder,
then, and in every such event (other than an event with respect to the Borrower
or Madison Avenue described in Sections 6.3 and 6.4) and at any time thereafter
during the continuance of such event, the Administrative Agent may, and at the
request of the Lenders holding a majority in outstanding principal amount of any
Note shall, by notice to the Borrower or, in the case of Note D, Madison Avenue,
take either or both of the following actions, at the same or different times:
(i) declare any such Note then outstanding to be due and payable in whole (or in
part, in which case any principal not so declared to be due and payable may
thereafter be declared to be due and payable), and thereupon the principal of
the Notes so declared to be due and payable, together with accrued interest
thereon and all fees and other obligations of the Borrower or Madison Avenue
accrued hereunder with respect to such Note, shall become due and payable
immediately, without presentment, demand, protest or other notice of any kind,
all of which are hereby waived by the Borrower; and in case of any Event of
Default with respect to the Borrower described in Sections 6.3 and 6.4, the
principal of the Notes then outstanding, together with accrued interest thereon
and all fees and other obligations of the Borrower accrued hereunder, shall
automatically become due and payable, without presentment, demand, protest or
other notice of any kind, all of which are hereby waived by the Borrower; and in
the case of any Event of Default with respect to Madison Avenue described in
Sections 6.3 and 6.4, the principal amount of Note D then outstanding, together
with accrued interest thereon and all fees and other obligations of Madison
Avenue accrued hereunder with respect to such Note, shall automatically become
due and payable, without presentment, demand, protest or other notice of any
kind, all of which are hereby waived by Madison Avenue, and (ii) may exercise
any other rights or remedies available under the other Loan Documents including
but not limited to the Collateral Agreements, at law or in equity.

            SECTION 6.10 Waiver of Past Defaults. The Required Lenders, by
notice to the Administrative Agent, may waive an existing Default or Event of
Default and its consequences, except a Default in the payment of principal or of
interest on any Note. Upon any such waiver, such Default shall cease to exist,
and any Event of Default arising therefrom shall be deemed to have been cured,
for every purpose of this Agreement; but no such waiver shall extend to any
subsequent or other Default or Event of Default or impair any right consequent
thereto.
<PAGE>

                                      25

            SECTION 6.11 Control by Required Holders. Subject to Article VII,
the Required Lenders may direct the time, method and place of conducting any
proceeding for any remedy available to the Administrative Agent or exercising
any trust or power conferred on the Administrative Agent.

            SECTION 6.12 Limitations on Suits and Actions. A Lender may not
pursue any remedy with respect to this Agreement or the Notes unless:

            (i) the Lender gives to the Administrative Agent written notice of a
      continuing Event of Default;

            (ii) the Required Lenders request to the Administrative Agent to
      pursue the remedy;

            (iii) such Lenders offer to the Administrative Agent reasonable
      indemnity against any costs, liability or expense to be incurred in
      compliance with such request;

            (iv) the Administrative Agent does not comply with the request
      within 60 days after receipt of the request and the offer of indemnity;
      and

            (v) during such 60-day period, the Required Lenders do not give the
      Administrative Agent a direction that is inconsistent with the request.


                                ARTICLE  VII.

                           The Administrative Agent

            Each of the Lenders hereby irrevocably appoints the Administrative
Agent as its agent and authorizes the Administrative Agent to take such actions
on its behalf and to exercise such powers as are delegated to the Administrative
Agent by the terms hereof, together with such actions and powers as are
reasonably incidental thereto.

            The Person serving as the Administrative Agent hereunder shall have
the same rights and powers in its capacity as a Lender as any other Lender and
may exercise the same as though it were not the Administrative Agent, and such
Person and its Affiliates may hold equity in, accept deposits from, lend money
to and generally engage in any kind of business with the Borrower or any
Subsidiary or other Affiliate thereof as if it were not the Administrative Agent
hereunder.

            Each Lender hereby authorizes the Administrative Agent, in its sole
discretion, to consent or withhold consent with respect to Sections 8, 9, 13 and
18 of the Security Deeds,
<PAGE>

                                      26

Deeds of Trust or Mortgages executed by Guarantors without seeking any direction
or input from any Lender.

            The Administrative Agent shall not have any duties or obligations
except those expressly set forth herein. Without limiting the generality of the
foregoing, (a) the Administrative Agent shall not be subject to any fiduciary or
other implied duties, regardless of whether a Default has occurred and is
continuing, (b) the Administrative Agent shall not have any duty to take any
discretionary rights and powers expressly contemplated hereby that the
Administrative Agent is required to exercise in writing by the Required Lenders,
and (c) except as expressly set forth herein, the Administrative Agent shall not
have any duty to disclose, and shall not be liable for the failure to disclose,
any information relating to the Borrower or any of its Subsidiaries that is
communicated to or obtained by the Person serving as Administrative Agent or any
of its Affiliates in any capacity. The Administrative Agent shall not be liable
for any action taken or not taken by it with the consent or at the request of
the Required Lenders or in the absence of its own gross negligence or wilful
misconduct. The Administrative Agent shall be deemed not to have knowledge of
any Default unless and until written notice thereof is given to the
Administrative Agent by the Borrower or a Lender, and the Administrative Agent
shall not be responsible for or have any duty to ascertain or inquire into (i)
any statement, warranty or representation made in or in connection with this
Agreement, (ii) the contents of any certificate, report or other document
delivered hereunder or in connection herewith, (iii) the performance or
observance of any of the covenants, agreements or other terms or conditions set
forth herein, (iv) the validity, enforceability, effectiveness or genuineness of
this Agreement or any other agreement, instrument or document or (v) the
satisfaction of any condition set forth herein, other than to confirm receipt of
items expressly required to be delivered to the Administrative Agent.

            The Administrative Agent shall be entitled to rely upon, and shall
not incur any liability for relying upon, any notice, request, certificate,
consent, statement, instrument, document or other writing believed by it to be
genuine and to have been signed or sent by the proper Person. The Administrative
Agent also may rely upon any statement made to it orally or by telephone and
believed by it to be made by the proper Person, and shall not incur any
liability for relying thereon. The Administrative Agent may consult with legal
counsel (who may be counsel for the Borrower), independent accountants and other
experts selected by it, and shall not be liable for any action taken or not
taken by it in accordance with the advice of any such counsel, accountants or
experts.

            The Administrative Agent may perform any and all its duties and
exercise its rights and powers by or through any one or more sub-agents
appointed by the Administrative Agent. The Administrative Agent and any such
sub-agent may perform any and all its duties and exercise its rights and powers
through their respective Related Parties. The exculpatory provisions of the
preceding paragraphs shall apply to any such sub-agent and to the Related
Parties of the Administrative Agent and any such sub-agent, and shall apply to
their respective activities provided for herein.
<PAGE>

                                      27

            Subject to the appointment and acceptance of a successor
Administrative Agent as provided in this paragraph, the Administrative Agent may
resign at any time by notifying the Lenders and the Borrower. Upon any such
resignation, the Required Lenders shall have the right, in consultation with the
Borrower, to appoint a successor. If no successor shall have been so appointed
by the Required Lenders and shall have accepted such appointment within 30 days
after the retiring Administrative Agent gives notice of its resignation, then
the retiring Administrative Agency may, on behalf of the Lenders, appoint a
successor Administrative Agent. Upon the acceptance of its appointment as
Administrative Agent hereunder by a successor, such successor shall succeed to
and become vested with all the rights, powers, privileges and duties of the
retiring Administrative Agent, and the retiring Administrative Agent shall be
discharged from its duties and obligations hereunder. The fees payable by the
Borrower to a successor Administrative Agent shall be the same as those payable
to its predecessor unless otherwise agreed between the Borrower and such
successor. After the Administrative Agent's resignation hereunder, the
provisions of this Article shall continue in effect for its benefit in respect
of any actions taken or omitted to be taken by it while it was acting as
Administrative Agent.

            Each Lender acknowledges that it has, independently and without
reliance upon the Administrative Agent or any other Lender and based on such
documents and information as it has deemed appropriate, made its own credit
analysis and decision to enter into this Agreement. Each Lender also
acknowledges that it will, independently and without reliance upon the
Administrative Agent or any other Lender and based on such documents and
information as it shall from time to time deem appropriate, continue to make its
own decisions in taking or not taking action under or based upon this Agreement,
any related agreement or any document furnished hereunder or thereunder.


                                ARTICLE  VIII.

                                 Miscellaneous

            SECTION 8.1 Notices. Any and all notices, elections or demands
permitted or required to be made under this Agreement 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 below, or at such other address as may be
supplied in writing in accordance with the terms of this paragraph. The date of
personal delivery or the second business day following the date of mailing, as
the case may be, shall be the date of such notice, election or demand. For the
purposes of this Agreement:
<PAGE>

                                      28

            The address of Borrower is:

            Cornerstone Properties Inc.
            126 East 56th Street
            New York, New York 10022
            Telecopier: (212) 605-7199
            Attention:  Mr. John S. Moody

            with a copy to:

            King & Spalding
            191 Peachtree Street
            Atlanta, Georgia 30303
            Telecopier: (404) 572-5148
            Attention:  William B. Fryer, Esq.

            The address of Administrative Agent is:

            Pensioenfonds PGGM
            Kroostweg-Noord 149
            Zeist, The Netherlands
            Telecopier: 011-31-30-696-3388
            Attention:  Mr. Jan van der Vlist
                        Ms. Anneke C. van de Puttelaar

            with a copy to:

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

or such other address as any party hereto may give the other pursuant to the
provisions hereof.

            SECTION 8.2 Waivers; Amendments.

            (a) No failure or delay by the Administrative Agent or any Lender in
exercising any right or power hereunder shall operate as a waiver thereof, nor
shall any single or partial exercise of any such right or power, or any
abandonment or discontinuance of steps to enforce such a right or power,
preclude any other or further exercise thereof or the exercise of any other
right or power. The rights and remedies of the Administrative Agent and the
Lenders hereunder
<PAGE>

                                      29

are cumulative and are not exclusive of any rights or remedies that they would
otherwise have. No waiver of any provision of this Agreement or consent to any
departure by the Borrower therefrom shall in any event be effective unless the
same shall be permitted by paragraph (b) of this Section, and then such waiver
or consent shall be effective only in the specific instance and for the purpose
for which given.

            (b) Neither this Agreement nor any provision hereof may be waived,
amended or modified except pursuant to an agreement or agreements in writing
entered into by the Borrower and the Required Lenders or by the Borrower and the
Administrative Agent with the consent of the Required Lenders; provided that no
such agreement shall (i) reduce the principal amount of any Note or reduce the
rate of interest thereon, or reduce any fees payable hereunder, without the
written consent of each Lender affected thereby, (ii) postpone the scheduled
date of payment of the principal amount of any Note, or any interest thereon, or
any fees payable hereunder, or reduce the amount of, waive or excuse any such
payment, without the written consent of each Lender affected thereby, (iii)
amend or alter the prepayment provision of any Note without the written consent
of each Lender affected thereby, (iv) change Section 2.7 in a manner that would
alter the pro rata sharing of payments required thereby, without the written
consent of each Lender, (v) change any of the provisions of this Section or the
definition of "Required Lenders" or any other provision hereof specifying the
number or percentage of Lenders required to waive, amend or modify any rights
hereunder or make any determination or grant any consent hereunder, without the
written consent of each Lender; (vi) release all or substantially all of the
Collateral which is the subject of the Note A Collateral Agreements or release
or discharge Note A Guarantors from any liability or indebtedness incurred under
the Loan Documents without the written consent of each holder of Note A, (vii)
release all or substantially all of the Collateral which is the subject of the
Note B Collateral Agreements or release or discharge any Note B Guarantors from
any liability or indebtedness incurred under the Loan Documents without the
written consent of each holder of Note B, (viii) release all or substantially
all of the Collateral which is the subject of the Note C Collateral Agreements
or release or discharge Note C Guarantors from any liability or indebtedness
incurred under the Loan Documents without the written consent of each holder of
Note C, or (ix) release all or substantially all of the Collateral which is the
subject of the Note D Collateral Agreements or release or discharge Note D
Guarantors from any liability or indebtedness incurred under the Loan Documents
without the written consent of each holder of Note D, provided further that no
such agreement shall amend, modify or otherwise affect the rights or duties of
the Administrative Agent hereunder without the prior written consent of the
Administrative Agent.

            SECTION  8.3  Expenses.

            (a) The Borrower and each Guarantor shall pay all reasonable
out-of-pocket expenses incurred by the Administrative Agent, including the
reasonable actually incurred fees, charges and disbursements, reasonably
actually incurred, of counsel for the Administrative Agent, in connection with
the enforcement or protection of its rights in connection with the Loan
<PAGE>

                                      30

Documents, including its rights under this Section 8.3, or in connection with
the Loans made hereunder.

            (b) Borrower and Madison Avenue shall indemnify and hold the
Administrative Agent and each Lender (each, an "Indemnified Party") harmless
from and against all obligations, liabilities, losses, costs, expenses, fines,
penalties or damages (including reasonable attorneys' fees and disbursements)
which the Administrative Agent or any Lender may actually incur by reason of
being the Administrative Agent or a Lender under any Loan Document or with
regard to the Collateral other than loss, obligations, liabilities, costs,
expenses, fines, penalties or damages caused by such Indemnified Party's willful
misconduct or gross negligence. Borrower and Madison Avenue shall defend each
Indemnified Party against any claim or litigation involving such Indemnified
Party for the same, and should such Indemnified Party incur such obligation,
liability, loss, cost, expense, fine, penalty or damage, then Borrower and
Madison Avenue shall reimburse such Indemnified Party upon demand.

            (c) To the extent permitted by applicable law, neither the Borrower
nor Madison Avenue shall assert, and each hereby waives, any claim against any
Indemnified Party, on any theory of liability, for special, indirect,
consequential or punitive damages (as opposed to direct or actual damages)
arising out of, in connection with, or as a result of, any Loan Document, the
Transactions, any Loan or the use of the proceeds thereof.

            SECTION 8.4 Replacement of Notes; Exchange of Notes. Upon receipt of
evidence reasonably satisfactory to Borrower of the loss, theft, destruction or
mutilation of any of the Notes, and in the case of any such loss, theft or
destruction, upon delivery of an indemnity agreement reasonably satisfactory to
Borrower or, in the case of any such mutilation, upon surrender and cancellation
of the Note, Borrower at Lender's expense will issue, in lieu thereof, a new
Note of like tenor, with appropriate recitations with respect to its replacement
of another note. The Borrower and Madison Avenue shall, from time to time at the
expense of the Lender requesting the same, issue one or more new Notes in
exchange for any Note. Such new Notes shall be Notes under the Loan Documents,
shall have an aggregate principal amount not exceeding the principal amount of
the Note for which such new Notes are exchanged and shall otherwise have the
same terms and conditions as the Note for which such new Notes; provided such
new Notes may be dated as of the date of such exchange.

            SECTION 8.5 Successors and Assigns.

            (a) The provisions of this Agreement shall be binding upon and inure
to the benefit of the parties hereto and their respective successors and assigns
permitted hereby, except that the Borrower may not assign or otherwise transfer
any of its rights or obligations hereunder without the prior written consent of
each Lender (and any attempted assignment or transfer by the Borrower without
such consent shall be null and void). Nothing in this Agreement, expressed or
implied, shall be construed to confer upon any Person (other than the parties
hereto, their
<PAGE>

                                      31

respective successors and assigns permitted hereby and, to the extent expressly
contemplated hereby, the Related Parties of each of the Administrative Agent and
the Lenders) and legal or equitable right, remedy or claim under or by reason of
this Agreement.

            (b) Any Lender may assign to one or more assignees all or a portion
of its rights and obligations under this Agreement and any Loan Document
(including all or a portion of the Notes at the time owing to it); provided that
(i) except in the case of an assignment to a Lender or an Affiliate of a Lender,
the Administrative Agent must give their prior written consent to such
assignment (which consent shall not be unreasonably withheld), (ii) except in
the case of an assignment to a Lender or an Affiliate of a Lender or an
assignment of the entire remaining amount of the indebtedness owed to the
assigning Lender, the amount of the indebtedness owed to the assigning Lender
subject to each such assignment (determined as of the date the Assignment and
Acceptance with respect to such assignment is delivered to the Administrative
Agent) shall not be less than $5,000,000 unless each of the Borrower and the
Administrative Agent otherwise consent, (iii) each partial assignment shall be
made as an assignment of a proportionate part of all the assigning Lender's
rights and obligations under this Agreement and any Loan Document, (iv) the
parties to each assignment shall execute and deliver to the Administrative Agent
an Assignment and Acceptance. Upon acceptance and recording, from and after the
effective date specified in each Assignment and Acceptance, the assignee
thereunder shall be a party hereto and, to the extent of the interest assigned
by such Assignment and Acceptance, have the rights and obligations of a Lender
under this Agreement and any Loan Document, and the assigning Lender thereunder
shall, to the extent of the interest assigned by such Assignment and Acceptance,
be released from its obligations under this Agreement and any Loan Document
(and, in the case of an Assignment and Acceptance covering all of the assigning
Lender's rights and obligations under this Agreement, such Lender shall cease to
be a party hereto but shall continue to be entitled to the benefits of Sections
2.6 and 8.3). Any assignment or transfer by a Lender of rights or obligations
under this Agreement that does not comply with this paragraph 8.5 shall be
treated for purposes of this Agreement as a sale by such Lender of a
participation in such rights and obligations in accordance with paragraph (e) of
this Section.

            (c) The Administrative Agent, acting for this purpose as an agent of
the Borrower, shall maintain at one of its offices a copy of each Assignment and
Acceptance delivered to it and a register for the recordation of the names and
addresses of the Lenders, and principal amount of the Notes owing to, each
Lender pursuant to the terms hereof from time to time (the "Register"). The
entries in the Register shall be conclusive, and the Borrower, the
Administrative Agent and the Lenders may treat each Person whose name is
recorded in the Register pursuant to the terms hereof as a Lender hereunder for
all purposes of this Agreement, notwithstanding notice to the contrary. The
Register shall be available for inspection by the Borrower and any Lender, at
any reasonable time and from time to time upon reasonable prior notice.

            (d) Upon its receipt of a duly completed Assignment and Acceptance
executed by an assigning Lender and an assignee, and any written consent to such
assignment required by
<PAGE>

                                      32

paragraph (b) of this Section, the Administrative Agent shall accept such
Assignment and Acceptance and record the information contained therein in the
Register. No assignment shall be effective for purposes of this Agreement unless
it has been recorded in the Register as provided in this paragraph.

            (e) Any Lender may, without the consent of the Borrower or the
Administrative Agent, sell participations to one or more banks or other entities
(a "Participant") in all or a portion of such Lender's rights and obligations
under this Agreement (including all or a portion of the Notes owing to it);
provided that (i) such Lender's obligations under this Agreement shall remain
unchanged, (ii) such Lender shall remain solely responsible to the other parties
hereto for the performance of such obligations and (iii) the Borrower, the
Administrative Agent and the other Lenders shall continue to deal solely and
directly with such Lender in connection with such Lender's rights and
obligations under this Agreement. Any agreement or instrument pursuant to which
a Lender sells such a participation shall provide that such Lender shall retain
the sole right to enforce this Agreement and to approve any amendment,
modification or waiver of any provision of this Agreement; provided that such
agreement or instrument may provide that such Lender will not, without the
consent of the Participant, agree to any amendment, modification or waiver
described in the first proviso to Section 8.5(b) that affects such Participant.
Subject to paragraph (f) of this Section, the Borrower agrees that each
Participant shall be entitled to the benefits of Sections 2.6 and 8.3 to the
same extent as if it were a Lender and had acquired its interest by assignment
pursuant to paragraph (b) of this Section.

            (f) A Participant shall not be entitled to receive any greater
payment under Section 2.6 than the applicable Lender would have been entitled to
receive with respect to the participation sold to such Participant, unless the
sale of the participation to such Participant is made with the Borrower's prior
written consent. A Participant that would be a Foreign Lender if it were a
Lender shall not be entitled to the benefits of Section 2.6 unless the Borrower
is notified of the participation sold to such Participant and such Participant
agrees, for the benefit of the Borrower, to comply with Section 2.6 as though it
were a Lender.

            (g) Any Lender may at any time pledge or assign a security interest
in all or any portion of its rights under this Agreement and the Loan Documents
to secure obligations of such Lender, including any such pledge or assignment to
a Federal Reserve Bank, and this Section shall not apply to any such pledge or
assignment of a security interest; provided that no such pledge or assignment of
a security interest shall release a Lender from any of its obligations hereunder
or substitute any such assignee for such Lender as a party hereto.

            SECTION 8.6 Survival. All covenants, agreements, representations and
warranties made by the Borrower herein and in the certificates or other
instruments delivered in connection with or pursuant to this Agreement shall be
considered to have been relied upon by the other parties hereto and shall
survive the execution and delivery of this Agreement and the Loan Documents and
the making of any Notes regardless of any investigation made by any such other
<PAGE>

                                      33

party or on its behalf and notwithstanding that the Administrative Agent or any
Lender may have had notice or knowledge of any Default or incorrect
representation or warranty at the time any credit is extended hereunder, and
shall continue in full force and effect as long as the principal of or any
accrued interest on any Note or any fee or any other amount payable under this
Agreement is outstanding and unpaid. The provisions of Sections 2.6 and 8.3 and
shall survive and remain in full force and effect regardless of the consummation
of the transactions contemplated hereby, the repayment of the Notes or the
termination of this Agreement or any provision hereof.

            SECTION 8.7 Counterparts; Integration; Effectiveness. This Agreement
may be executed in counterparts (and by different parties hereto on different
counterparts), each of which shall constitute an original, but all of which when
taken together shall constitute a single contract. This Agreement shall become
effective when it shall have been executed by the Administrative Agent and when
the Administrative Agent shall have received counterparts hereof which, when
taken together, bear the signatures of each of the other parties hereto, and
thereafter shall be binding upon and inure to the benefit of the parties hereto
and their respective successors and assigns. Delivery of an executed counterpart
of a signature page of this Agreement by telecopy shall be effective as delivery
of a manually executed counterpart of this Agreement.

            SECTION 8.8 CHOICE OF LAW. THE TERMS OF THIS AGREEMENT SHALL BE
GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF
THE STATE OF NEW YORK (EXCLUSIVE OF ANY RULES AS TO CONFLICT OF LAWS) AND THE
LAWS OF THE UNITED STATES APPLICABLE THEREIN. SERVICE OF PROCESS ON THE BORROWER
OR MADISON AVENUE IN ANY ACTION ARISING OUT OF OR RELATING TO THIS AGREEMENT OR
THE TRANSACTION SHALL BE EFFECTIVE IF MAILED TO THE PARTY IN ACCORDANCE WITH
SECTION 8.1 HEREOF. NOTHING HEREIN SHALL PRECLUDE THE ADMINISTRATIVE AGENT OR
ANY LENDER FROM BRINGING SUIT OR TAKING OTHER LEGAL ACTION IN ANY OTHER
JURISDICTION.

            SECTION 8.9 WAIVER OF JURY TRIAL. EACH PARTY HERETO HEREBY WAIVES,
TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY RIGHT IT MAY HAVE TO A
TRIAL BY JURY IN ANY LEGAL PROCEEDING DIRECTLY OR INDIRECTLY ARISING OUT OF OR
RELATING TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY (WHETHER
BASED ON CONTRACT, TORT OR ANY OTHER THEORY). EACH PARTY HERETO (A) CERTIFIES
THAT NO REPRESENTATIVE, AGENT OR ATTORNEY OR ANY OTHER PARTY HAS REPRESENTED,
EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PARTY WOULD NOT, IN THE EVENT OF
LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER AND (B) ACKNOWLEDGES THAT IT
AND THE OTHER PARTIES HERETO HAVE BEEN INDUCED TO ENTER INTO THIS AGREEMENT BY,
AMONG OTHER THINGS, THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION.
<PAGE>

                                      34

            SECTION 8.10 Headings. Article and Section headings and the Table of
Contents used herein are for convenience of reference only, are not part of this
Agreement and shall not affect the constitution of, or be taken into
consideration in interpreting, this Agreement.

            SECTION 8.11 Non-Recourse. Except as specifically provided for in
this Section 8.11, none of the Borrower, DIHC of Georgia, Inc., Charlotte Plaza
Properties, Inc., Balsam Mountain, Inc., DIHC Marble Place Properties, DIHC
Dearborn Properties, Inc., DIHC Dearborn Venture nor any of their respective
officers, directors, shareholders, agents, employees or representatives
(collectively, the "Exculpated Parties") shall be personally liable for the
payment of any sums due hereunder or the performance of any obligations of the
Borrower or any Guarantor hereunder, or under the other Loan Documents. No
judgment for the repayment of the Notes or interest thereon or any other amount
payable pursuant to any of the Loan Documents will be enforced against any of
the Exculpated Parties personally, or any property of any of the Exculpated
Parties other than the Collateral and any other security now or hereafter
expressly granted under the Loan Documents in any action to enforce this Loan
Agreement or otherwise realize upon any security now or hereafter expressly
granted under the Loan Documents or to collect any amount payable hereunder or
under the other Loan Documents. Notwithstanding the foregoing:

            1. Nothing herein contained shall be construed as prohibiting the
      Administrative Agent or any Lender from exercising any and all remedies
      which the Loan Documents permit, including the right to bring actions or
      proceedings against the Borrower, DIHC of Georgia, Inc., Charlotte Plaza
      Properties, Inc., Balsam Mountain, Inc., DIHC Marble Place Properties,
      DIHC Dearborn Properties, Inc., DIHC Dearborn Venture and other Exculpated
      Parties and to enter a judgment against any Borrower, DIHC of Georgia,
      Inc., Charlotte Plaza Properties, Inc., Balsam Mountain, Inc., DIHC Marble
      Place Properties, DIHC Dearborn Properties, Inc., DIHC Dearborn Venture
      and other Exculpated Parties, so long as the exercise of any remedy does
      not extend to execution against or recovery out of any property of the
      Borrower, DIHC of Georgia, Inc., Charlotte Plaza Properties, Inc., Balsam
      Mountain, Inc., DIHC Marble Place Properties, DIHC Dearborn Properties,
      Inc., DIHC Dearborn Venture or any other Exculpated Party other than the
      Collateral expressly granted under the Loan Documents;

            2. Each of the Borrower, DIHC of Georgia, Inc., Charlotte Plaza
      Properties, Inc., Balsam Mountain, Inc., DIHC Marble Place Properties,
      DIHC Dearborn Properties, Inc., and DIHC Dearborn Venture shall be fully
      and personally liable for, and the other Exculpated Parties (to the extent
      the other Exculpated Parties would be liable outside of the provisions of
      this paragraph), shall be fully and personally liable for (i) misapplying
      any condemnation awards or insurance awards attributable to the
      Collateral, to the full extent of such awards so misapplied, (ii)
      misapplying any security deposits attributable to the Collateral, to the
      full extent of such deposits so misapplied, (iii) collecting any rents
      more than forty (40) days in advance in violation of any covenant
      contained in the Loan
<PAGE>

                                      35

      Documents, to the full extent of such rents so collected in advance, (iv)
      committing fraud or intentional misrepresentation in connection with the
      operation of the Collateral or the making of the Loans, to the full extent
      of any loss, damage, expense or costs (including reasonable attorneys'
      fees) actually incurred by the Administrative Agent or any Lender
      resulting from such fraud or misrepresentation, (v) failing to pay in
      order of priority: real estate taxes or assessments, (or escrow accounts
      established therefor), operating and maintenance expenses relating to the
      Collateral, other sums required by the Loan Documents, deposits into a
      required reserve account, capital expenditures, management fees, leasing
      fees and expenses, marketing and advertising costs and debt service or
      other amounts due on the Indebtedness, but only to the extent of any gross
      revenues from the Collateral that were available to pay such expenses but
      were not so used during the period beginning six (6) months prior to
      either (A) any Exculpated Party's receipt of notice of default under any
      of the Loan Documents or (B) the occurrence of a Default and continuing
      through the date the Administrative Agent or any Lender takes title to the
      Collateral; (vi) the seizure or forfeiture of the Collateral due to the
      criminal activity by the Borrower or any Guarantor, any constituent
      partner of the Borrower or any Guarantor, or any of their respective
      shareholders, partners, officers, employees or agents, in the full amount
      of the loss incurred by the Administrative Agent or any Lender as a result
      of such seizure or forfeiture.

            This Section shall impose no limitation on any other Exculpated
Party's personal liability under and the exercise of any of the Administrative
Agent's rights under any indemnity from any Exculpated Party to the
Administrative Agent including but not limited to, the Environmental
Indemnification Agreement of even date herewith from any Guarantor and the
Borrower to the Administrative Agent with regard to the Collateral except as may
be expressly set forth therein.

            This Section shall impose no limitation on or prejudice to the
rights of the Administrative Agent or the Lender to proceed against any entity
or person whatsoever, including the Exculpated Parties, with respect to the
enforcement of any sums due hereunder or under any of the other Loan Documents
or any part thereof, any master leases, or any similar rights of payment that
may be entered into after the date hereof, except as may be expressly set forth
therein.

            SECTION 8.12 Confidentiality. Each of the Administrative Agent and
the Lenders agrees to maintain the confidentiality of the Information (as
defined below), except that Information may be disclosed (a) to its and its
Affiliates, directors, officers, employees and agents, including accountants,
legal counsel and other advisors (it being understood that the Persons to whom
such disclosure is made will be informed of the confidential nature of such
Information and instructed to keep such Information confidential), (b) to the
extent requested by any regulatory authority, (c) to the extent required by
applicable laws or regulations or by any subpoena or similar legal process, (d)
to any other party to this Agreement, (e) in connection with the exercise
<PAGE>

                                      36

of any remedies hereunder or any suit, action or proceeding relating to this
Agreement or the enforcement of rights hereunder, (f) subject to an agreement
containing provisions substantially the same as those of this Section, to any
assignee of or Participant in, or any prospective assignee of or Participant in,
any of its rights or obligations under this Agreement, (g) with the consent of
the Borrower or (h) to the extent such Information (i) becomes publicly
available other than as a result of a breach of this Section or (ii) becomes
available to the Administrative Agent or any Lender on a nonconfidential basis
from a source other than the Borrower. For the purposes of this Section,
"Information" means all information received from the Borrower relating to the
Borrower or its business, other than any such Information that is available to
the Administrative Agent or any Lender on a nonconfidential basis prior to
disclosure by the Borrower; provided that, in the case of Information received
from the Borrower after the date hereof, such Information is clearly identified
at the time of delivery as confidential. Any Person required to maintain the
confidentiality of Information as provided in this Section shall be considered
to have complied with its obligation to do so if such Person has exercised the
same degree of care to maintain the confidentiality of such Information as such
Person would accord to its own confidential information.

            SECTION  8.13  Intercompany Indebtedness.  The Borrower and each
Guarantor agrees and shall cause each of their respective subsidiaries to agree
that all obligations and liabilities owing to them ("Junior Claims") from any
Guarantor party to the Recourse Guarantor (a "Recourse Guarantor") shall be
subordinate and junior in right of payment to such Recourse Guarantor's
obligations under the Recourse Guaranty. So long as any amounts owing by the
Recourse Guarantor under the Recourse Guaranty are due and remain unpaid, no
direct or indirect payment, whether in cash or otherwise, shall be made by such
Recourse Guarantor on account of any Junior Claim. Any payment or distribution
in contravention of the foregoing shall be deemed received in trust by the
Borrower or any Guarantor or any subsidiary thereof and shall be immediately
turned over to the Administrative Agent for application to the amounts owing by
such Recourse Guarantor under the Recourse Guaranty.
<PAGE>

                                      37

            IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be duly executed by their respective authorized officers as of the day and year
first above written.

                                    CORNERSTONE PROPERTIES INC.


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


                                    By:   /s/ R. Dimock
                                         -----------------------
                                    Name: R. Dimock
                                    Title:


                                    CHARLOTTE PLAZA PROPERTIES, INC.
                                    a Georgia corporation


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

                                                [CORPORATE SEAL]


                                    BALSAM MOUNTAIN, INC.,
                                    a Georgia corporation


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

                                                [CORPORATE SEAL]
<PAGE>

                                      38

                                    DIHC OF GEORGIA, INC.,
                                    a Georgia corporation


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

                                                [CORPORATE SEAL]


                                    DIHC MARBLE PLACE PROPERTIES, INC.,
                                    a Georgia corporation


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

                                                [CORPORATE SEAL]


                                    DIHC DEARBORN PROPERTIES, INC.,
                                    a Georgia corporation

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

                                                [CORPORATE SEAL]
<PAGE>

                                      39

                                    DIHC DEARBORN VENTURE
                                    By:   DIHC Marble Place Properties, Inc.

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

                                                      [SEAL]

                                    By:   DIHC Dearborn Properties, Inc.

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

                                                      [SEAL]

                                    CHARLOTTE OFFICE TOWER
                                    ASSOCIATES,
                                    a North Carolina partnership

                                    By:   Balsam Mountain, Inc.,
                                          a general partner

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

                                                            [SEAL]

                                    By:   Charlotte Plaza Properties, Inc.,
                                          a general partner

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

                                                            [SEAL]
<PAGE>

                                      40

                                    BRYCE MOUNTAIN, INC.,
                                    a Georgia corporation

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

                                                      [CORPORATE SEAL]

                                    DIHC PROPERTIES I, INC.,
                                    a Georgia corporation

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

                                                [CORPORATE SEAL]


                                    DEARBORN INTERESTS,
                                    a Georgia general partnership

                                    By:   DIHC Dearborn Properties, Inc.,
                                    a general partner


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

                                                      [SEAL]
<PAGE>

                                      41

                                    By:   DIHC Dearborn Venture
                                          a Georgia general partnership

                                          By:   DIHC Dearborn Properties, Inc.,
                                                      a general partner


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

                                                            [SEAL]


                                          By:   DIHC Marble Place
                                                Properties, Inc.,
                                                a general partner


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

                                     [SEAL]



                                    CSTONE-OAKBROOK, INC.,
                                    a Delaware corporation


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


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

                                                      [CORPORATE SEAL]
<PAGE>

                                      42

                                    CSTONE-527 MADISON, INC.,
                                    a Delaware corporation


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


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

                                                      [CORPORATE SEAL]


                                    STICHTING PENSIOENFONDS VOOR DE
                                    GEZONDHEID, GEESTELIJKE EN
                                    MAATSCHAPPELIJKE BELANGEN,
                                    individually and as Administrative Agent


                                    By:    /s/ Jan H.W.R. van der Vlist
                                          ------------------------------
                                    Name: Jan H.W.R. van der Vlist
                                    Title: Attorney-in-Fact


                                    By:    /s/ Anneke C. van de Puttelaar
                                          --------------------------------
                                    Name: Anneke C. van de Puttelaar
                                    Title: Attorney-in-Fact



                                    DUTCH INSTITUTIONAL HOLDING
                                    COMPANY, INC.


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

                                 SCHEDULE 1.1

                                    LENDERS



                        Stichting Pensioenfonds Voor de Gezondheid,
                        Geestelijke en Maatschappelijke Belangen
                        Kroostweg-Noord 149
                        Zeist, The Netherlands

                        Dutch Institutional Holding Company, Inc.
                        c/o DIHC Management Corporation
                        200 Galleria Parkway, N.W., Suite 200
                        Atlanta, Georgia 30339
<PAGE>

                                  SCHEDULE 2.2
                                  FORM OF NOTES

THIS SECURITY (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A TRANSACTION EXEMPT
FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), AND ALL APPLICABLE STATE SECURITIES LAWS (THE "STATE
LAWS") AND MAY NOT BE SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH
REGISTRATION OR AN APPLICABLE EXEMPTION THEREFROM. THE EXEMPTION PROVIDED BY
RULE 144A UNDER THE SECURITIES ACT MAY BE AVAILABLE TO PERMIT SALE OR TRANSFER
OF THIS SECURITY TO QUALIFIED INSTITUTIONAL BUYERS (AS DEFINED IN RULE 144A
UNDER THE SECURITIES ACT) WITHOUT REGISTRATION. THE HOLDER HEREOF, BY PURCHASING
THIS SECURITY, AGREES FOR THE BENEFIT OF THE OBLIGOR THAT (A) THIS SECURITY MAY
BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT REGISTRATION, ONLY (1) TO
THE OBLIGOR, (2) TO A PERSON WHO THE SELLER REASONABLY BELIEVES IS A QUALIFIED
INSTITUTIONAL BUYER PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A
QUALIFIED INSTITUTIONAL BUYER THAT IS AWARE THAT THE RESALE, PLEDGE OR OTHER
TRANSFER IS BEING MADE IN RELIANCE ON RULE 144A, (3) PURSUANT TO AN EXEMPTION
FROM REGISTRATION UNDER THE SECURITIES ACT IN ACCORDANCE WITH REGULATION S, RULE
144 OR RULE 145 UNDER THE SECURITIES ACT OR (4) PURSUANT TO ANOTHER APPLICABLE
EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND STATE
LAWS (IF AVAILABLE) TO THE EXTENT IT DELIVERS TO THE OBLIGOR AND THE OBLIGEE AN
OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE OBLIGOR THAT SUCH TRANSFER IS
IN COMPLIANCE WITH THE SECURITIES ACT AND STATE LAWS, AND THAT (B) THE HOLDER
WILL, AND WILL REQUIRE AS A CONDITION OF TRANSFER EACH SUBSEQUENT HOLDER TO
AGREE IN WRITING TO, NOTIFY ANY PURCHASER OF ANY SECURITY FROM IT OF THE RESALE
RESTRICTIONS SET FORTH IN (A) ABOVE.

                          DEFERRED PURCHASE PRICE NOTE
                                    (Note A)
$55,000,000                                              Dated: October __, 1997

      FOR VALUE RECEIVED, the undersigned CORNERSTONE PROPERTIES INC., a Nevada
corporation (the "Obligor"), HEREBY PROMISES TO PAY to the order of DUTCH
INSTITUTIONAL HOLDING COMPANY, INC., a Delaware corporation, and its successors
and assigns (the "Obligee") having an address at 200 Galleria Parkway, N.W.,
Suite 2000, Atlanta, Georgia 30339, or at such other place as the holder of this
Note may designate from time to time in writing, the sum of FIFTY-FIVE MILLION
AND NO/100 DOLLARS ($55,000,000), together with all accrued and unpaid interest
thereon.
<PAGE>

      Interest shall accrue from the date hereof to and including 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 seven and 28/100 percent (7.28%) per annum. Principal shall be due and
payable in full on October _, 2000 (the "Maturity Date"). Accrued interest shall
be due and payable quarterly in arrears on January 1, April 1, July 1 and
October 1 of each calendar year until the Maturity Date, at which time all
accrued and unpaid interest shall be due and payable in full. Both principal and
interest are payable in lawful money of the United States of America in same day
funds.

      In the event any payment is not paid by Obligor within five (5) Business
Days following the due date for such payment, Obligor shall pay to Obligee a
late charge for the month during which such payment is not made when due, and
for each month or fraction thereof that such sum remains unpaid, equal to five
percent (5%) of such payment. In addition, in the event Obligor fails to pay any
installment of principal and interest on the date due, the unpaid amount shall
accrue interest at the Default Rate until paid. "Default Rate" shall be the
higher of (a) 10.28% or (b) 3% above the "prime rate" as announced by The Chase
Manhattan Bank from time to time.

      The indebtedness evidenced by this Note may not be prepaid, either in
whole or in part, without the express written consent of the Obligee; provided,
however, the Obligor may prepay the indebtedness evidenced by this Note without
any penalty on or after the date which is sixty (60) days prior to the Maturity
Date.

      This Deferred Purchase Price Note is issued and delivered pursuant to that
certain Note and Collateral Agency Agreement dated as of the date hereof
executed by and between Obligor, certain of its subsidiaries, Obligee and
Stichting Pensioenfonds voor de Gezondheid, Geestelijke en Maatschappelijke
Belangen, on its own behalf and as administrative agent, as amended,
supplemented or modified (the "Loan Agreement") and shall be governed by the
provisions of the Loan Agreement. Upon and after the occurrence of an Event of
Default under the Loan Agreement (as such term is defined therein), this Note
may, and without demand, notice or legal process of any kind, be declared and
immediately shall become due and payable. This Note is guarantied and secured by
the Guaranty and the Collateral Agreements referred to in the Loan Agreement and
is entitled to the benefits thereof.

      Except as provided for herein, Obligee's right, title and interest in and
to this Note are freely assignable without the consent of Obligor by Obligee, in
whole or in part, and any such assignment hereof by Obligee shall operate to
vest in such assignee all rights, titles, interests and powers herein conferred
upon Obligee. Without limiting the generality of the foregoing, Obligor
acknowledges that Obligee 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.


                                       2
<PAGE>

      The liability of the Obligor hereunder is subject to the non-recourse
limitations set forth in Section 8.11 of the Loan Agreement.

      If at any time the interest rate applicable to this Note, together with
all fees, charges and other amounts which are treated as interest on this Note
under applicable law (collectively the "Charges"), shall exceed the maximum
lawful rate (the "Maximum Rate") which may be contracted for, charged, taken,
received or reserved by Obligee in accordance with applicable law, the rate of
interest payable in respect of this Note, together with all Charges payable in
respect hereof, shall be limited to the Maximum Rate and, to the extent lawful,
the interest and Charges that would have been payable in respect of this Note
but were not payable as a result of the operation of this provision shall be
cumulated and the interest and Charges payable to the Obligor in respect of
other Notes or periods shall be increased (but not above the Maximum Rate
therefor) until such cumulated amount, together with interest thereon at the
Federal Funds Effective Rate to the date of repayment, shall have been received
by Obligor.

      Time is of the essence hereunder.

      To the extent permitted by applicable law, Obligor and, by its acceptance
hereof the holder hereof, irrevocably waives all right to trial by jury in any
action, proceeding or counterclaim arising out of or relating to this Note,

      The terms of this Note shall be governed by, and shall be construed and
enforced in accordance with, the laws of the State of New York (exclusive of any
rules as to conflict of laws) and the laws of the United States applicable
therein. Service of process on the Obligor in any action arising out of or
relating to this Note shall be effective if mailed to the Obligor in accordance
with Section 8.1 of the Loan Agreement. Nothing herein shall preclude the
Obligee from bringing suit or taking other legal action in any other
jurisdiction.

      Capitalized terms used and not defined herein shall have the meaning
ascribed to them in the Loan Agreement.

      This Note has been executed, delivered and accepted at New York, New York.

                                    CORNERSTONE PROPERTIES INC.,
                                    a Nevada corporation

                                    By:__________________________
                                    Its:_________________________

                                    By:__________________________
                                    Its:_________________________

                                                [CORPORATE SEAL]

                                       3
<PAGE>

THIS SECURITY (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A TRANSACTION EXEMPT
FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), AND ALL APPLICABLE STATE SECURITIES LAWS (THE "STATE
LAWS") AND MAY NOT BE SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH
REGISTRATION OR AN APPLICABLE EXEMPTION THEREFROM. THE EXEMPTION PROVIDED BY
RULE 144A UNDER THE SECURITIES ACT MAY BE AVAILABLE TO PERMIT SALE OR TRANSFER
OF THIS SECURITY TO QUALIFIED INSTITUTIONAL BUYERS (AS DEFINED IN RULE 144A
UNDER THE SECURITIES ACT) WITHOUT REGISTRATION. THE HOLDER HEREOF, BY PURCHASING
THIS SECURITY, AGREES FOR THE BENEFIT OF THE OBLIGOR THAT (A) THIS SECURITY MAY
BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT REGISTRATION, ONLY (1) TO
THE OBLIGOR, (2) TO A PERSON WHO THE SELLER REASONABLY BELIEVES IS A QUALIFIED
INSTITUTIONAL BUYER PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A
QUALIFIED INSTITUTIONAL BUYER THAT IS AWARE THAT THE RESALE, PLEDGE OR OTHER
TRANSFER IS BEING MADE IN RELIANCE ON RULE 144A, (3) PURSUANT TO AN EXEMPTION
FROM REGISTRATION UNDER THE SECURITIES ACT IN ACCORDANCE WITH REGULATION S, RULE
144 OR RULE 145 UNDER THE SECURITIES ACT OR (4) PURSUANT TO ANOTHER APPLICABLE
EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND STATE
LAWS (IF AVAILABLE) TO THE EXTENT IT DELIVERS TO THE OBLIGOR AND THE OBLIGEE AN
OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE OBLIGOR THAT SUCH TRANSFER IS
IN COMPLIANCE WITH THE SECURITIES ACT AND STATE LAWS, AND THAT (B) THE HOLDER
WILL, AND WILL REQUIRE AS A CONDITION OF TRANSFER EACH SUBSEQUENT HOLDER TO
AGREE IN WRITING TO, NOTIFY ANY PURCHASER OF ANY SECURITY FROM IT OF THE RESALE
RESTRICTIONS SET FORTH IN (A) ABOVE.

                          DEFERRED PURCHASE PRICE NOTE
                                    (Note B)
$10,000,000                                              Dated: October __, 1997

      FOR VALUE RECEIVED, the undersigned CORNERSTONE PROPERTIES INC., a Nevada
corporation (the "Obligor"), HEREBY PROMISES TO PAY to the order of DUTCH
INSTITUTIONAL HOLDING COMPANY, INC., a Delaware corporation, and its successors
and assigns (the "Obligee") having an address at 200 Galleria Parkway, N.W.,
Suite 2000, Atlanta, Georgia 30339, or at such other place as the holder of this
Note may designate from time to time in writing, the sum of TEN MILLION AND
NO/100 DOLLARS ($ 10,000,000), together with all accrued and unpaid interest
thereon.

      Interest shall accrue from the date hereof to and including 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 seven and 28/100 percent (7.28%) per annum; provided, however, that during
the

                                       1
<PAGE>

period from the date hereof up to and including the date which is earlier of (1)
the date upon which the Obligor sells, transfers and conveys its interest in the
parcel of undeveloped real property which is the subject of the Dearborn
Security Documents or (2) October __, 2000, no interest shall accrue on the
indebtedness evidenced by this Note. Principal shall be due and payable in full
on October __, 2000 (the "Maturity Date"). Accrued interest shall be due and
payable quarterly in arrears on January 1, April 1, July 1 and October 1 of each
calendar year until the Maturity Date, at which time all accrued and unpaid
interest shall be due and payable in full.

      In the event any payment is not paid by Obligor within five (5) Business
Days following the due date for such payment, Obligor shall pay to Obligee a
late charge for the month during which such payment is not made when due, and
for each month or fraction thereof that such sum remains unpaid, equal to five
percent (5%) of such payment. In addition, in the event Obligor fails to pay any
installment of principal and interest on. the date due, the unpaid amount shall
accrue interest at the Default Rate until paid. "Default Rate" shall be the
higher of (a) 10.28% or (b) 3% above the "prime rate" as announced by The Chase
Manhattan Bank from time to time.

      The indebtedness evidenced by this Note may not be prepaid, either in
whole or in part, without the express written consent of the Obligee; provided,
however, the Obligor may prepay the indebtedness evidenced by this Note without
any penalty on or after the date which is sixty (60) days prior to the Maturity
Date.

      This Deferred Purchase Price Note is issued and delivered pursuant to that
certain Note and Collateral Agency Agreement dated as of the date hereof
executed by and between Obligor, certain of its subsidiaries, Obligee and
Stichting Pensioenfonds voor de Gezondheid, Geestelijke en Maatschappelijke
Belangen, on its own behalf and as administrative agent, as amended,
supplemented or modified (the "Loan Agreement") and shall be governed by the
provisions of the Loan Agreement. Upon and after the occurrence of an Event of
Default under the Loan Agreement (as such term is defined therein), this Note
may, and without demand, notice or legal process of any kind, be declared and
immediately shall become due and payable. This Note is guarantied and secured by
the Guaranty and the Collateral Agreements referred to in the Loan Agreement and
is entitled to the benefits thereof.

      Except as provided for herein, Obligee's right, title and interest in and
to this Note are freely assignable without the consent of Obligor by Obligee, in
whole or in part, and any such assignment hereof by Obligee shall operate to
vest in such assignee all rights, titles, interests and powers herein conferred
upon Obligee. Without limiting the generality of the foregoing, Obligor
acknowledges that Obligee 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.

      The liability of the Obligor hereunder is subject to the non-recourse
limitations set forth in Section 8.11 of the Loan Agreement.


                                       2
<PAGE>

      If at any time the interest rate applicable to this Note, together with
all fees, charges and other amounts which are treated as interest on this Note
under applicable law (collectively the "Charges"), shall exceed the maximum
lawful rate (the "Maximum Rate") which may be contracted for, charged, taken,
received or reserved by Obligee in accordance with applicable law, the rate of
interest payable in respect of this Note, together with all Charges payable in
respect hereof, shall be limited to the Maximum Rate and, to the extent lawful,
the interest and Charges that would have been payable in respect of this Note
but were not payable as a result of the operation of this provision shall be
cumulated and the interest and Charges payable to the Obligor in respect of
other Notes or periods shall be increased (but not above the Maximum Rate
therefor) until such cumulated amount, together with interest thereon at the
Federal Funds Effective Rate to the date of repayment, shall have been received
by Obligor.

      Time is of the essence hereunder.

      To the extent permitted by applicable law, Obligor and, by its acceptance
hereof the holder hereof, hereby irrevocably waive all right to trial by jury in
any action, proceeding or counterclaim arising out of or relating to this Note.

      The terms of this Note shall be governed by, and shall be construed and
enforced in accordance with, the laws of the State of New York (exclusive of any
rules as to conflict of laws) and the laws of the United States applicable
therein. Service of process on the Obligor in any action arising out of or
relating to this Note shall be effective if mailed to the Obligor in accordance
with Section 8.1 of the Loan Agreement. Nothing herein shall preclude the
Obligee from bringing suit or taking other legal action in any other
jurisdiction.

      Capitalized terms used and not defined herein shall have the meaning
ascribed to them in the Loan Agreement.

      This Note has been executed, delivered and accepted at New York, New York.

                                    CORNERSTONE PROPERTIES INC.,
                                    a Nevada corporation

                                    By:__________________________
                                    Its:_________________________

                                    By:__________________________
                                    Its:_________________________


                                                [CORPORATE SEAL]


                                       3
<PAGE>

THIS SECURITY (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A TRANSACTION EXEMPT
FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), AND ALL APPLICABLE STATE SECURITIES LAWS (THE "STATE
LAWS") AND MAY NOT BE SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH
REGISTRATION OR AN APPLICABLE EXEMPTION THEREFROM. THE EXEMPTION PROVIDED BY
RULE 144A UNDER THE SECURITIES ACT MAY BE AVAILABLE TO PERMIT SALE OR TRANSFER
OF THIS SECURITY TO QUALIFIED INSTITUTIONAL BUYERS (AS DEFINED IN RULE 144A
UNDER THE SECURITIES ACT) WITHOUT REGISTRATION. THE HOLDER HEREOF, BY PURCHASING
THIS SECURITY, AGREES FOR THE BENEFIT OF THE OBLIGOR THAT (A) THIS SECURITY MAY
BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT REGISTRATION, ONLY (1) TO
THE OBLIGOR, (2) TO A PERSON WHO THE SELLER REASONABLY BELIEVES IS A QUALIFIED
INSTITUTIONAL BUYER PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A
QUALIFIED INSTITUTIONAL BUYER THAT IS AWARE THAT THE RESALE, PLEDGE, OR OTHER
TRANSFER IS BEING MADE IN RELIANCE ON RULE 144A, (3) PURSUANT TO AN EXEMPTION
FROM REGISTRATION UNDER THE SECURITIES ACT IN ACCORDANCE WITH REGULATION S, RULE
144 OR RULE 145 UNDER THE SECURITIES ACT OR (4) PURSUANT TO ANOTHER APPLICABLE
EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND STATE
LAWS (IF AVAILABLE) TO THE EXTENT IT DELIVERS TO THE OBLIGOR AND THE OBLIGEE AN
OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE OBLIGOR THAT SUCH TRANSFER IS
IN COMPLIANCE WITH THE SECURITIES ACT AND STATE LAWS, AND THAT (B) THE HOLDER
WILL, AND WILL REQUIRE AS A CONDITION OF TRANSFER EACH SUBSEQUENT HOLDER TO
AGREE IN WRITING TO, NOTIFY ANY PURCHASER OF ANY SECURITY FROM IT OF THE RESALE
RESTRICTIONS SET FORTH IN (A) ABOVE.

                          DEFERRED PURCHASE PRICE NOTE
                                    (Note C)
$30,000,000                                               Dated: October __,1997

      FOR VALUE RECEIVED, the undersigned CORNERSTONE PROPERTIES INC., a Nevada
corporation (the "Obligor"), HEREBY PROMISES TO PAY to the order of DUTCH
INSTITUTIONAL HOLDING COMPANY, INC., a Delaware corporation, and its successors
and assigns (the "Obligee") having an address at 200 Galleria Parkway, N. W.,
Suite 2000, Atlanta, Georgia 30339, or at such other place as the holder of this
Note may designate from time to time in writing, the sum of THIRTY MILLION AND
NO/100 DOLLARS ($30,000,000), together with all accrued and unpaid interest
thereon.

      Interest shall accrue from the date hereof to and including 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 seven and 47/100 percent (7.47%) per annum. Principal shall be due and
payable

                                       1
<PAGE>

in full on October __, 2004 (the "Maturity Date"). Accrued interest shall be due
and payable quarterly in arrears on January 1, April 1, July 1 and October 1 of
each calendar year until the Maturity Date, at which time all accrued and unpaid
interest shall be due and payable in full. Both principal and interest are
payable in lawful money of the United States of America in same day funds.

      In the event any payment is not paid by Obligor I within five (5) Business
Days following the due date for such payment, Obligor shall pay to Obligee a
late charge for the month during which such payment is not made when due, and
for each month or fraction thereof that such sum remains unpaid, equal to five
percent (5%) of such payment. In addition, in the event Obligor fails to pay any
installment of principal and interest on the date due, the unpaid amount shall
accrue interest at the Default Rate until paid. "Default Rate" shall be the
higher of (a) 10.47% or (b) 3% above the "prime rate" as announced by The Chase
Manhattan Bank from time to time.

      The indebtedness evidenced by this Note may not be prepaid, either in
whole or in part, without the express written consent of the Obligee; provided,
however, the Obligor may prepay the indebtedness evidenced by this Note without
any penalty on or after the date which is sixty (60) days prior to the Maturity
Date.

      This Deferred Purchase Price Note is issued and delivered pursuant to that
certain Note and Collateral Agency Agreement dated as of the date hereof
executed by and between Obligor, certain of its subsidiaries, Obligee and
Stichting Pensioenfonds voor de Gezondheid, Geestelijke en Maatschappelijke
Belangen, on its own behalf and as administrative agent, as amended,
supplemented or modified (the "Loan Agreement") and shall be governed by the
provisions of the Loan Agreement. Upon and after the occurrence of an Event of
Default under the Loan Agreement (as such term is defined therein), this Note
may, and without demand, notice or legal process of any kind, be declared and
immediately shall become due and payable. This Note is guarantied and secured by
the Guaranty and the Collateral Agreements referred to in the Loan Agreement and
is entitled to the benefits thereof.

      Except as provided for herein, Obligee's right, title and interest in and
to this Note are freely assignable without the consent of Obligor by Obligee, in
whole or in part, and any such assignment hereof by Obligee shall operate to
vest in such assignee all rights, titles, interests and powers herein conferred
upon Obligee. Without limiting the generality of the foregoing, Obligor
acknowledges that Obligee 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.

      The liability of the Obligor hereunder is subject to the non-recourse
limitations set forth in Section 8.11 of the Loan Agreement.

      If at any time the interest rate applicable to this Note, together with
all fees, charges and other amounts which are treated as interest on this Note
under applicable law (collectively the

                                       2
<PAGE>

"Charges"), shall exceed the maximum lawful rate (the "Maximum Rate") which may
be contracted for, charged, taken, received or reserved by Obligee in accordance
with applicable law, the rate of interest payable in respect of this Note,
together with all Charges payable in respect hereof, shall be limited to the
Maximum Rate and, to the extent lawful, the interest and Charges that would have
been payable in respect of this Note but were not payable as a result of the
operation of this provision shall be cumulated and the interest and Charges
payable to the Obligor in respect of other Notes or periods shall be increased
(but not above the Maximum Rate therefor) until such cumulated amount, together
with interest thereon at the Federal Funds Effective Rate to the date of
repayment, shall have been received by Obligor.

      Time is of the essence hereunder.

      To the extent permitted by applicable law, Obligor and, by its acceptance
hereof the holder hereof, hereby irrevocably waive all right to trial bv jury in
any action, proceeding or counterclaim arising out of or relating to this Note.

      The terms of this Note shall be governed by, and shall be construed and
enforced in accordance with, the laws of the State of New York (exclusive of any
rules as to conflict of laws) and the laws of the United States applicable
therein. Service of process on the Obligor in any action arising out of or
relating to this Note shall be effective if mailed to the Obligor in accordance
with Section 8.1 of the Loan Agreement. Nothing herein shall preclude the
Obligee from bringing suit or taking other legal action in any other
jurisdiction.

      Capitalized terms used and not defined herein shall have the meaning
ascribed to them in the Loan Agreement.

      This Note has been executed, delivered and accepted at New York, New York.

                          CORNERSTONE PROPERTIES INC.,
                                    a Nevada corporation

                                    By:__________________________
                                    Its:_________________________

                                    By:__________________________
                                    Its:_________________________


                                                [CORPORATE SEAL]



                                       3
<PAGE>

THIS SECURITY (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A TRANSACTION EXEMPT
FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), AND ALL APPLICABLE STATE SECURITIES LAWS (THE "STATE
LAWS") AND MAY NOT BE SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH
REGISTRATION OR AN APPLICABLE EXEMPTION THEREFROM. THE EXEMPTION PROVIDED BY
RULE 144A UNDER THE SECURITIES ACT MAY BE AVAILABLE TO PERMIT SALE OR TRANSFER
OF THIS SECURITY TO QUALIFIED INSTITUTIONAL BUYERS (AS DEFINED IN RULE 144A
UNDER THE SECURITIES ACT) WITHOUT REGISTRATION. THE HOLDER HEREOF, BY PURCHASING
THIS SECURITY, AGREES FOR THE BENEFIT OF THE OBLIGOR THAT (A) THIS SECURITY MAY
BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT REGISTRATION, ONLY (1) TO
THE OBLIGOR, (2) TO A PERSON WHO THE SELLER REASONABLY BELIEVES IS A QUALIFIED
INSTITUTIONAL BUYER PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A
QUALIFIED INSTITUTIONAL BUYER THAT IS AWARE THAT THE RESALE, PLEDGE OR OTHER
TRANSFER IS BEING MADE IN RELIANCE ON RULE 144A, (3) PURSUANT TO AN EXEMPTION
FROM REGISTRATION UNDER THE SECURITIES ACT IN ACCORDANCE WITH REGULATION S, RULE
144 OR RULE 145 UNDER THE SECURITIES ACT OR (4) PURSUANT TO ANOTHER APPLICABLE
EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND STATE
LAWS (IF AVAILABLE) TO THE EXTENT IT DELIVERS TO THE OBLIGOR AND THE OBLIGEE AN
OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE OBLIGOR THAT SUCH TRANSFER IS
IN COMPLIANCE WITH THE SECURITIES ACT AND STATE LAWS, AND THAT (B) THE HOLDER
WILL, AND WILL REQUIRE AS A CONDITION OF TRANSFER EACH SUBSEQUENT HOLDER TO
AGREE IN WRITING TO, NOTIFY ANY PURCHASER OF ANY SECURITY FROM IT OF THE RESALE
RESTRICTIONS SET FORTH IN (A) ABOVE.

                          DEFERRED PURCHASE PRICE NOTE
                                    (Note D)
$35,000,000                                               Dated: October _, 1997

      FOR VALUE RECEIVED, the undersigned CSTONE-527 MADISON, INC., a Delaware
corporation (the "Obligor"), HEREBY PROMISES TO PAY to the order of DUTCH
INSTITUTIONAL HOLDING COMPANY, INC., a Delaware corporation, and its successors
and assigns (the "Obligee") having an address at 200 Galleria Parkway, N.W.,
Suite 2000, Atlanta, Georgia 30339, or at such other place as the holder of this
Note may designate from time to time in writing, the sum of THIRTY-FIVE MILLION
AND NO/100 DOLLARS ($35,000,000), together with all accrued and unpaid interest
thereon.

      Interest shall accrue from the date hereof to and including 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 seven and 47/100 percent (7.47%) per annum. Principal shall be due and
payable

                                       1
<PAGE>

in full on October _, 2004 (the "Maturity Date"). Accrued interest shall be due
and payable quarterly in arrears on January 1, April 1, July 1 and October 1 of
each calendar year until the Maturity Date, at which time all accrued and unpaid
interest shall be due and payable in full. Both principal and interest are
payable in lawful money of the United States of America in same day funds.

      In the event any payment is not paid by Obligor within five (5) Business
Days following the due date for such payment, Obligor shall pay to Obligee a
late charge for the month during which such payment is not made when due, and
for each month or fraction thereof that such sum remains unpaid, equal to five
percent (5%) of such payment. In addition, in the event Obligor fails to pay any
installment of principal and interest on the date due, the unpaid amount shall
accrue interest at the Default Rate until paid. "Default Rate" shall be the
higher of (a) 10.47% or (b) 3% above the "prime rate" as announced by The Chase
Manhattan Bank from time to time.

      The indebtedness evidenced by this Note may not be prepaid, either in
whole or in part, without the express written consent of the Obligee; provided,
however, the Obligor may prepay the indebtedness evidenced by this Note without
any penalty on or after the date which is sixty (60) days prior to the Maturity
Date.

      This Deferred Purchase Price Note is issued and delivered pursuant to that
certain Note and Collateral Agency Agreement dated as of the date hereof
executed by and between Cornerstone Properties Inc., certain of its subsidiaries
including Obligor, Obligee and Stichting Pensioenfonds voor de Gezondheid,
Geestelijke en Maatschappelijke Belangen, on its own behalf and as
administrative agent, as amended, supplemented or modified (the "Loan
Agreement") and shall be governed by the provisions of the Loan Agreement. Upon
and after the occurrence of an Event of Default under the Loan Agreement (as
such term is defined therein), this Note may, and without demand, notice or
legal process of any kind, be declared and immediately shall become due and
payable. This Note is guarantied and secured by the Guaranty and the Collateral
Agreements referred to in the Loan Agreement and is entitled to the benefits
thereof.

      Except as provided for herein, Obligee's right, title and interest in and
to this Note are freely assignable without the consent of Obligor by Obligee, in
whole or in part, and any such assignment hereof by Obligee shall operate to
vest in such assignee all rights, titles, interests and powers herein conferred
upon Obligee. Without limiting the generality of the foregoing, Obligor
acknowledges that Obligee 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.

      If at any time the interest rate applicable to this Note, together with
all fees, charges and other amounts which are treated as interest on this Note
under applicable law (collectively the "Charges"), shall exceed the maximum
lawful rate (the "Maximum Rate") which may be contracted for, charged, taken,
received or reserved by Obligee in accordance with applicable law, the rate of
interest payable in respect of this Note, together with all Charges payable in
respect hereof, shall be limited to the Maximum Rate and, to the extent lawful,
the interest and Charges that would have

                                       2
<PAGE>

been payable in respect of this Note but were not payable as a result of the
operation of this provision shall be cumulated and the interest and Charges
payable to the Obligor in respect of other Notes or periods shall be increased
(but not above the Maximum Rate therefor) until such cumulated amount, together
with interest thereon at the Federal Funds Effective Rate to the date of
repayment, shall have been received by Obligor.

      Time is of the essence hereunder.

      To the extent permitted by applicable law, Obligor and, by its acceptance
hereof the holders hereof, hereby irrevocably waive all right to trial by jury
in any action, proceeding or counterclaim arising out of or relating to this
Note.

      The terms of this Note shall be governed by, and shall be construed and
enforced in accordance with, the laws of the State of New York (exclusive of any
rules as to conflict of laws) and the laws of the United States applicable
therein. Service of process on the Obligor in any action arising out of or
relating to this Note shall be effective if mailed to the Obligor in accordance
with Section 8.1 of the Loan Agreement. Nothing herein shall preclude the
Obligee from bringing suit or taking other legal action in any other
jurisdiction.

      Capitalized terms used and not defined herein shall have the meaning
ascribed to them in the Loan Agreement.

      This Note has been executed, delivered and accepted at New York, New York.

      Pursuant to the Note Modification and Extension Agreement dated as of the
date hereof between Obligor and Obligee, this Deferred Purchase Price Note
amends and restates certain existing notes.

                                    CSTONE-527 MADISON, INC.,
                                    a Delaware corporation

                                    By:__________________________
                                    Its:_________________________

                                    By:__________________________
                                    Its:_________________________


                                                [CORPORATE SEAL]

                                       3
<PAGE>

THIS SECURITY (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A TRANSACTION EXEMPT
FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), AND ALL APPLICABLE STATE SECURITIES LAWS (THE "STATE
LAWS") AND MAY NOT BE SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH
REGISTRATION OR AN APPLICABLE EXEMPTION THEREFROM. THE EXEMPTION PROVIDED BY
RULE 144A UNDER THE SECURITIES ACT MAY BE AVAILABLE TO PERMIT SALE OR TRANSFER
OF THIS SECURITY TO QUALIFIED INSTITUTIONAL BUYERS (AS DEFINED IN RULE 144A
UNDER THE SECURITIES ACT) WITHOUT REGISTRATION. THE HOLDER HEREOF, BY PURCHASING
THIS SECURITY, AGREES FOR THE BENEFIT OF THE OBLIGOR THAT (A) THIS SECURITY MAY
BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT REGISTRATION, ONLY (1) TO
THE OBLIGOR, (2) TO A PERSON WHO THE SELLER REASONABLY BELIEVES IS A QUALIFIED
INSTITUTIONAL BUYER PURCHASING FOR ITS OWN ACCOUNT OR FOR THE ACCOUNT OF A
QUALIFIED INSTITUTIONAL BUYER THAT IS AWARE THAT THE RESALE, PLEDGE OR OTHER
TRANSFER IS BEING MADE IN RELIANCE ON RULE 144A, (3) PURSUANT TO AN EXEMPTION
FROM REGISTRATION UNDER THE SECURITIES ACT IN ACCORDANCE WITH REGULATION S, RULE
144 OR RULE 145 UNDER THE SECURITIES ACT OR (4) PURSUANT TO ANOTHER APPLICABLE
EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND STATE
LAWS (IF AVAILABLE) TO THE EXTENT IT DELIVERS TO THE OBLIGOR AND THE OBLIGEE AN
OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE OBLIGOR THAT SUCH TRANSFER IS
IN COMPLIANCE WITH THE SECURITIES ACT AND STATE LAWS, AND THAT (B) THE HOLDER
WILL, AND WILL REQUIRE AS A CONDITION OF TRANSFER EACH SUBSEQUENT HOLDER TO
AGREE IN WRITING TO, NOTIFY ANY PURCHASER OF ANY SECURITY FROM IT OF THE RESALE
RESTRICTIONS SET FORTH IN (A) ABOVE.

                          DEFERRED PURCHASE PRICE NOTE
                                    (Note E)
$120,000,000                                             Dated: October __, 1997

      FOR VALUE RECEIVED, the undersigned CORNERSTONE PROPERTIES INC., a Nevada
corporation (the "Obligor"), HEREBY PROMISES TO PAY to the order of STICHTING
PENSIOENFONDS VOOR DE GEZONDHEID, GEESTELIJKE EN MAATSCHAPPELIJKE BELANGEN, a
foundation formed according to the laws of The Netherlands, and its successors
and assigns (the "Obligee") having an address at Kroostweg-Noord 149, Zeist, The
Netherlands , or at such other place as the holder of this Note may designate
from time to time in writing, the sum of ONE HUNDRED TWENTY MILLION AND NO/100
DOLLARS ($120,000,000), together with all accrued and unpaid interest thereon.

      Interest shall accrue from the date hereof to and including 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


                                       1
<PAGE>

year, and shall be calculated on the outstanding principal balance hereunder at
an annual rate of interest equal to seven and 54/100 percent (7.54%) per annum.
Principal shall be due and payable in full on October __, 2007 (the "Maturity
Date"). Accrued interest shall be due and payable quarterly in arrears on
January 1, April 1, July 1 and October 1 of each calendar year until the
Maturity Date, at which time all accrued and unpaid interest shall be due and
payable in full. Both principal and interest are payable in lawful money of the
United States of America in same day funds.

      In the event any payment is not paid by Obligor within five (5) Business
Days following the due date for such payment, Obligor shall pay to Obligee a
late charge for the month during which such payment is not made when due, and
for each month or fraction thereof that such sum remains unpaid, equal to five
percent (5%) of such payment. In addition, in the event Obligor fails to pay any
installment of principal and interest on the date due, the unpaid amount shall
accrue interest at the Default Rate until paid. "Default Rate" shall be the
higher of (a) 10.54% or (b) 3% above the "prime rate" as announced by The Chase
Manhattan Bank from time to time.

      The indebtedness evidenced by this Note may not be prepaid, either in
whole or in part, without the express written consent of the Obligee; provided,
however, the Obligor may prepay the indebtedness evidenced by this Note without
any penalty on or after the date which is sixty (60) days prior to the Maturity
Date.

      This Deferred Purchase Price Note is issued and delivered pursuant to that
certain Note and Collateral Agency Agreement dated as of the date hereof
executed by and between Obligor, certain of its subsidiaries, Dutch
Institutional Holding Company, Inc. and Obligee, on its own behalf and as
administrative agent, as amended, supplemented or modified (the "Loan
Agreement") and shall be governed by the provisions of the Loan Agreement. Upon
and after the occurrence of an Event of Default under the Loan Agreement (as
such term is defined therein), this Note may, and without demand, notice or
legal process of any kind, be declared and immediately shall become due and
payable. This Note is guarantied and secured by the Guaranty and the Collateral
Agreements referred to in the Loan Agreement and is entitled to the benefits
thereof.

      Except as provided for herein, Obligee's right, title and interest in and
to this Note are freely assignable without the consent of Obligor by Obligee, in
whole or in part, and any such assignment hereof by Obligee shall operate to
vest in such assignee all rights, titles, interests and powers herein conferred
upon Obligee. Without limiting the generality of the foregoing, Obligor
acknowledges that Obligee 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.

      The liability of the Obligor hereunder is subject to the non-recourse
limitations set forth in Section 8.11 of the Loan Agreement.


                                       2
<PAGE>

      If at any time the interest rate applicable to this Note, together with
all fees, charges and other amounts which are treated as interest on this Note
under applicable law (collectively the "Charges"), shall exceed the maximum
lawful rate (the "Maximum Rate") which may be contracted for, charged, taken,
received or reserved by Obligee in accordance with applicable law, the rate of
interest payable in respect of this Note, together with all Charges payable in
respect hereof, shall be limited to the Maximum Rate and, to the extent lawful,
the interest and Charges that would have been payable in respect of this Note
but were not payable as a result of the operation of this provision shall be
cumulated and the interest and Charges payable to the Obligor in respect of
other Notes or periods shall be increased (but not above the Maximum Rate
therefor) until such cumulated amount, together with interest thereon at the
Federal Funds Effective Rate to the date of repayment, shall have been received
by Obligor.

      Time is of the essence hereunder.

      To the extent permitted by applicable law, Obligor and, by its acceptance
hereof the holders hereof, hereby irrevocably waives all right to trial by jury
in any action, proceeding or counterclaim arising out of or relating to this
Note.

      Capitalized terms used and not defined herein shall have the meaning
ascribed to such terms in the Loan Agreement.

      The terms of this Note shall be governed by, and shall be construed and
enforced in accordance with, the laws of the State of New York (exclusive of any
rules as to conflict of laws) and the laws of the United States applicable
therein. Service of process on the Obligor in any action arising out of or
relating to this Note shall be effective if mailed to the Obligor in accordance
with Section 8.1 of the Loan Agreement. Nothing herein shall preclude the
Obligee from bringing suit or taking other legal action in anv other
jurisdiction.

      This Note has been executed, delivered and accepted at New York, New York.

                                    CORNERSTONE PROPERTIES INC.,
                                    a Nevada corporation

                                    By:__________________________
                                    Its:_________________________


                                    By:__________________________
                                    Its:_________________________
                                                [CORPORATE SEAL]

                                       2
<PAGE>

                                  SCHEDULE 2.3A
                                FORMS OF GUARANTY


                                    GUARANTY

      GUARANTY, dated as of October _, 1997, of the undersigned, CHARLOTTE
OFFICE TOWER ASSOCIATES, a North Carolina partnership ("Charlotte Office"),
BRYCE MOUNTAIN, INC., a Georgia corporation ("Bryce"), DIHC PROPERTIES I, INC.,
a Georgia corporation ("Properties"), DEARBORN INTERESTS, a Georgia general
partnership ("Dearborn"), CSTONE-OAKBROOK, INC., a Delaware corporation
("Oakbrook"), CSTONE- 527 MADISON, INC., a Delaware corporation ("Madison
Avenue") (collectively referred to herein as "Guarantors") in favor of STICHTING
PENSIOENFONDS VOOR DE GEZONDHEID, GEESTELIJKE EN MAATSCHA-PPELIJKE BELANGEN, a
foundation formed according to the laws of The Netherlands, as administrative
agent for the holders of the Notes (as defined below) ("Agent").

                              W I T N E S S E T H :

      WHEREAS, Cornerstone Properties Inc., a Nevada corporation (the
"Borrower"), and certain of its subsidiaries have executed and delivered to the
Agent that certain Note and Collateral Agency Agreement (the "Loan Agreement")
as amended, supplemented or modified from time to time, dated as of the date
hereof pursuant to which Borrower will execute and deliver that certain Deferred
Purchase Price Note (Note A) dated as of the date hereof in the original
principal amount of $55,000,000 ("Note A"), that certain Deferred Purchase Price
Note (Note B) dated as of the date hereof in the original principal amount of
$10,000,000 ("Note B"), that certain Deferred Purchase Price Note (Note C) dated
as of the date hereof in the original principal amount of $30,000,000 ("Note C")
and that certain Deferred Purchase Price Note (Note E) dated as of the date
hereof in the original principal amount of $120,000,000 ("Note E"), and CStone
527 Madison, Inc. ("Madison Avenue") will execute and deliver that certain
Deferred Purchase Price Note (Note D) dated as of the date hereof in the
original principal amount of $35,000,000 ("Note D") (Note A, Note B, Note C,
Note D and Note E, as amended, supplemented, replaced, exchanged or modified
from time to time, are collectively referred to herein as the "Notes").

      WHEREAS, Borrower directly or indirectly owns 100% of the equity interests
of each of the Guarantors and Guarantors will derive direct and indirect
economic benefits from the execution and delivery of the Loan Agreement and the
Notes and the transactions related thereto;

      WHEREAS, each of the Guarantors has secured this Guaranty by the pledge of
its rights in and to certain real property or other assets, as more fully
described in the Collateral Agreements.

      NOW, THEREFORE, in consideration of the premises and the covenants
hereinafter contained, and to induce the Lenders to accept the Notes, it is
agreed as follows:


<PAGE>

      1. DEFINITIONS. Capitalized terms used herein shall have the meanings
assigned to them in the Loan Agreement, unless the context otherwise requires or
unless otherwise defined herein.

            References to this "Guaranty" shall mean this Guaranty, including
all amendments, modifications and supplements and any exhibits or schedules to
any of the foregoing, and shall refer to the Guaranty as the same may be in
effect at the time such reference becomes operative.

            References to "Guaranteed Obligations" shall mean the unpaid
principal of and interest on the Notes and all other obligations and liabilities
of the Borrower, Madison Avenue and the Guarantors to the Agent and the Lenders
(including, without limitation, interest accruing at the then applicable rate
provided in the Notes after maturity of the Notes and interest accruing at the
then applicable rate provided in the Notes after the filing of any petition in
bankruptcy, or the commencement of any insolvency, reorganization or like
proceeding, relating to the Borrower or Madison Avenue, whether or not a claim
for post-filing or post-petition interest is allowed in such proceeding),
whether direct or indirect, absolute or contingent, due or to become due, or now
existing or hereafter incurred, which may arise under, out of, or in connection
with, this Agreement or any other Loan Document.

            References to "Loan Documents" shall mean the Notes, the Loan
Agreement, and the Collateral Agreements.

      2. THE GUARANTY. The guaranty of each of the Guarantors hereunder is as
follows:

            2.1 Guaranty of the Notes. Each of the Guarantors hereby
unconditionally guarantees to the Agent, and its successors, endorsees,
transferees and assigns, for its benefit and for the benefit of the holders of
the Notes, the prompt payment (whether at stated maturity, by acceleration or
otherwise) and performance when due of the Guaranteed Obligations. Each of the
Guarantors agrees that this Guaranty is a guaranty of payment and performance
and not of collection, and that its obligations under this Guaranty shall be
primary, absolute and unconditional, irrespective of, and unaffected by:

            (a) the genuineness, validity, regularity, enforceability or any
      future amendment of, or change in this Guaranty, the Loan Agreement, any
      other Loan Document or any other agreement, document or instrument to
      which Borrower, Madison Avenue and/or any of the Guarantors is or are or
      may become a party;

            (b) the absence of any action to enforce this Guaranty, the Loan
      Agreement, the Notes or any other Loan Document or the waiver or consent
      by the Agent or any Lenders with respect to any of the provisions thereof,


                                       2
<PAGE>

            (c) the existence, value or condition of, or failure to perfect its
      Lien against, any security for the Guaranteed Obligations or any action,
      or the absence of any action, by the Agent or Lenders in respect thereof
      (including, without limitation, the release of any such security); or

            (d) any other action or circumstances which might otherwise
      constitute a legal or equitable discharge or defense of a surety or
      guarantor,

it being agreed by each of the Guarantors that, except as set forth in Section
2.4 hereof, its obligations under this Guaranty shall not be discharged until
the payment and performance, in full, of the Guaranteed Obligations. Each of the
Guarantors shall be regarded, and shall be in the same position, as principal
debtor with respect to the Notes.

            2.2 Maximum Liability. The maximum liability of each Guarantor
hereunder as of any date shall in no event exceed the Maximum Guaranty Liability
(as hereinafter defined) of such Guarantor as of such date. It is the intention
of the parties hereto that in no event shall any of Guarantor's obligations
under this Guaranty constitute or result in a violation of any applicable
fraudulent conveyance, fraudulent transfer or similar law or any relevant
jurisdiction. Therefore, in the event that this Guaranty would, but for the
second preceding sentence, constitute or result in such violation, then the
liability of any Guarantor under this Guaranty shall be reduced to the maximum
amount permissible under the applicable fraudulent conveyance, fraudulent
transfer or similar laws.

            (a) "Maximum Guaranty Liability" of any Guarantor as of any date
      shall mean the greater of the following amounts: (i) the sum of the
      following (without duplication) as of such date: (A) the outstanding
      amount of all loans, advances, guarantees, capital contributions or other
      investments made by the Borrower and Madison Avenue to or for the benefit
      of such Guarantor, plus (B) the fair market value of all property
      transferred by the Borrower and Madison Avenue to such Guarantor, plus (C)
      the fair market value of all benefits received by such Guarantor's
      business and other relationships with the Borrower and Madison Avenue,
      plus (D) with respect to each transfer or benefit referred to in the
      foregoing clauses (A), (B) and (C), interest on the amount transferred or
      benefit received, such interest to accrue at the highest rate under the
      Notes until the same are repaid to the Borrower and Madison Avenue; and
      (ii) the greatest of the Fair Value Net Worth of such Guarantor as of (A)
      September 30, 1997, (B) each fiscal quarter-end of such person thereafter
      occurring on or prior to the date of determination of Maximum Guaranty
      Liability, (C) the date on which enforcement of this Guaranty is sought,
      and (D) the date on which a case under Title 11 of the United States Code
      is commenced with respect to the Borrower or such Guarantor. "Fair Value
      Net Worth" of a Guarantor as of any date shall mean (i) the fair value or
      fair saleable value (as the case may be, determined in accordance with
      applicable federal and state laws affecting creditors' rights and
      governing determinations of insolvency of debtors) of such Guarantor's
      assets (including such Guarantor's rights to contribution and subrogation
      hereunder) as of such date, minus (ii) the

                                       3
<PAGE>

      sum of $ 1.00 and the amount of all liabilities of such person (determined
      in accordance with such laws) as of such date but excluding (x) this
      Guaranty and (y) any liabilities subordinated in right of payment to this
      Guaranty.

            (b) Each Guarantor agrees that the Guaranteed Obligations may at any
      time and from time to time exceed the Maximum Guaranty Liability of such
      Guarantor, and may exceed the aggregate Maximum Guaranty Liability of all
      Guarantors, without impairing this Guaranty or affecting the rights and
      remedies of any beneficiary hereunder.

            2.3 Contribution. In the event that any Guarantor (a "Funding
Guarantor") shall make any payment or payments under this Guaranty, such Funding
Guarantor shall have contribution rights against each other Guarantor (each, a
"Contributing Guarantor") up to the amount of such Contributing Guarantor's
Maximum Guaranty Liability.

            2.4 Termination of Guaranty. Notwithstanding anything to the
contrary contained herein, (a) any and all liability or obligation of Charlotte
Office and Bryce hereunder shall terminate and be discharged in full upon
payment and performance, in full, of Note A, provided, however, no Default or
Event of Default shall have occurred and be continuing at the time of such
termination or discharge; (b) any and all liability or obligation of Dearborn
hereunder shall terminate and be discharged in full upon payment and
performance, in full, of Note B, provided, however, no Default or Event of
Default shall have occurred and be continuing at the time of such termination or
discharge; (c) any and all liability or obligation of Oakbrook and Madison
Avenue hereunder shall terminate and be discharged in full upon payment and
performance, in full, of Note C and Note D, provided, however, no Default or
Event of Default shall have occurred and be continuing at the time of such
termination and discharge; and (d) any and all liability or obligation of
Properties hereunder shall terminate and be discharged in full upon payment and
performance, in full, of Note E, provided, however, no Default or Event of
Default shall have occurred and be continuing at the time of such termination or
discharge.

            2.5 Enforcement of Guaranty. In no event shall the Agent or any
Lender have any obligation (although it is entitled, at its option) to proceed
against the Borrower or any other person or any real or personal property
pledged to secure the Guaranteed Obligations before proceeding against any of
the Guarantors, and the Agent or any Lender may proceed, prior or subsequent to,
or simultaneously with, the enforcement of the Agent's or any Lender's rights
hereunder, to exercise any right or remedy which it may have against any
property, real or personal, as a result of any Lien it may have as security for
all or any portion of the Guaranteed Obligations.

            2.6 Waiver. In addition to the waivers contained in Section 2.1
hereof, each of the Guarantors waives, and agrees that it shall not at any time
insist upon, plead or in any manner whatever claim or take the benefit or
advantage of, any appraisal, valuation, stay, extension, marshalling of assets
or redemption laws, or exemption, whether now or at any time hereafter in force,
which may delay, prevent or otherwise affect the performance by the Guarantor of
its obligations under, or the enforcement by Agent or any Lender of, this
Guaranty. Each of the

                                       4
<PAGE>

Guarantors hereby waives diligence, presentment and demand (whether for
nonpayment or protest or of acceptance, maturity, extension of time, change in
nature or form of the Notes, the Loan Agreement, or any other Loan Document,
acceptance of further security, release of further security, composition or
agreement arrived at as to the amount of, or the terms of, the Loan Agreement,
the Notes or any other Loan Document, notice of adverse change in Borrower's or
Madison Avenue's financial condition or any other fact which might materially
increase the risk to the Guarantor) with respect to the Guaranteed Obligations
or all other demands whatsoever and waives the benefit of all provisions of law
which are or might be in conflict with the terms of this Guaranty. Each of the
Guarantors represents, warrants and agrees that, as of the date of this
Guaranty, its obligations under this Guaranty are not subject to any offense or
defense against the Agent, any Lender, Madison Avenue or Borrower of any kind.

            2.7 Benefits of Guaranty. The provisions of this Guaranty are for
the benefit of the Agent, the Lenders and their respective successors,
transferees, endorsees and assigns, and nothing herein contained shall impair,
as between Borrower, Madison Avenue, the Agent and the Lenders, the obligations
of Borrower or Madison Avenue under the Notes, the Loan Agreement or any other
Loan Document.

            2.8 Modification of Note, etc. If the Agent or any Lender shall at
any time or from time to time, with or without the consent of, the Guarantors:

            (a) change or extend the manner, place or terms of payment of, or
      renew or alter all or any portion of, the Notes, the Loan Agreement or any
      other Loan Document;

            (b) take any action under or in respect of the Loan Agreement, the
      Notes or any other Loan Document in the exercise of any remedy, power or
      privilege contained therein or available to it at law, equity or
      otherwise, or waive or refrain from exercising any such remedies, powers
      or privileges;

            (c) amend or modify, in any manner whatsoever, the Notes, the Loan
      Agreement or any other Loan Document;

            (d) extend or waive the time for any of the Guarantor's, Borrower's
      or other person's performance of, or compliance with, any term, covenant
      or agreement on its part to be performed or observed under the Notes, the
      Loan Agreement or any other Loan Document, or waive such performance or
      compliance or consent to a failure of, or departure from, such performance
      or compliance;

            (e) take and hold security or collateral for the Guaranteed
      Obligations or sell, exchange, release, dispose of, or otherwise deal
      with, any property pledged, mortgaged or conveyed, or in which the Agent
      or any Lender has been granted a Lien, to secure any indebtedness of any
      of the Guarantors, Madison Avenue or Borrower to the Agent or any Lender;

                                       5
<PAGE>

            (f) release anyone who may be liable in any manner for the payment
      of any amounts owed by any of the Guarantors, Madison Avenue or Borrower
      to the Agent or any Lender;

            (g) modify or terminate the terms of any intercreditor or
      subordination agreement pursuant to which claims of other creditors of any
      of the Guarantors, Madison Avenue or Borrower are subordinated to the
      claims of the Agent or any Lender; and/or

            (h) apply any sums by whomever paid or however realized to any
      amounts owing by any of the Guarantors, Madison Avenue or Borrower to the
      Agent or any Lender in such manner as the Agent or any Lender shall
      determine in their discretion;

then neither the Agent nor any Lender shall incur any liability to the
Guarantors pursuant hereto as a result thereof, and no such action shall impair
or release the obligations of any of the Guarantors under this Guaranty.

            2.9 Reinstatement. This Guaranty shall remain in full force and
effect and continue to be effective in the event any petition be filed by or
against Borrower or any Guarantor for liquidation or reorganization, in the
event Borrower or any of the Guarantors becomes insolvent or makes an assignment
for the benefit of creditors or in the event a receiver or trustee be appointed
for all or any significant part of Borrower's or Guarantor's assets, and shall
continue to be effective or be reinstated, as the case may be, if at any time
payment and performance of the Guaranteed Obligations, or any part thereof, is,
pursuant to applicable law, rescinded or reduced in amount, or must otherwise be
restored or returned by the Agent or any Lender, whether as a "voidable
preference", "fraudulent conveyance", or otherwise, all as though such payment
or performance had not been made. In the event that any payment, or any part
thereof, is rescinded, reduced, restored or returned, the Guaranteed Obligations
shall be reinstated and deemed reduced only by such amount paid and not so
rescinded, reduced, restored or returned.

            2.10 Election of Remedies, Etc., Any election of remedies which
results in the denial or impairment of the right of the Agent or any Lender to
seek a deficiency judgment against Borrower or Madison Avenue shall not impair
the obligation of any of the Guarantors to pay the full amount of the Guaranteed
Obligations. In the event the Agent or any Lender shall bid at any foreclosure
or trustee's sale or at any private sale permitted by law, the Agent or any
Lender may bid all or less than the amount of the Guaranteed Obligations and the
amount of such bid need not be paid by the Agent or any Lender but shall be
credited against the Guaranteed Obligations. The amount of the successful bid at
any such sale, whether the Agent, any Lender or any other party is the
successful bidder, shall be conclusively deemed to be the fair market value of
the collateral.

            2.11 Continuing Guaranty. The Guarantor agrees that this Guaranty is
a continuing guaranty and shall remain in full force and effect until the
payment in full of all Guaranteed Obligations except as set forth in Section
2.4.


                                       6
<PAGE>

            3. REPRESENTATIONS AND WARRANTIES. Each of the Guarantors makes the
following representations and warranties to the Agent and each Lender:

            3.1 Corporate Power; Authorization; Enforceability. The execution,
delivery and performance of this Guaranty by the Guarantor will not violate any
law or regulation, or any order or decree of any court or governmental
instrumentality, will not conflict with or result in the breach of, or
constitute a default under any indenture, mortgage, deed of trust, lease,
agreement or other instrument to which the Guarantor is a party or by which
Guarantor or any of its property is bound, will not result in the creation or
imposition of any Lien upon any of the property of Guarantor and the same do not
require the consent or approval of any governmental body, agency, authority or
any other person except those already obtained. This Guaranty has been duly
executed and delivered by or on behalf of Guarantor.

            3.2 Affirmation of Covenants, Representations and Warranties.
Guarantor affirms and ratifies the covenants, representations and warranties
contained in Articles III, IV and V of the Loan Agreement and agrees and
covenants that it shall comply with the terms of such covenants, representations
and warranties.

      4. PERMITTED ASSIGNMENT BY AGENT. The Agent or any Lender may freely
assign its rights and delegate its duties under this Guaranty, but no such
assignment or delegation shall increase or diminish the obligations of the
Guarantors hereunder.

      5. FURTHER ASSURANCES. Each of the Guarantors agrees, upon the written
request of the Agent, to execute and deliver to the Agent, from time to time,
any additional instruments or documents reasonably considered necessary by the
Agent to cause this Guaranty to be, become or remain valid and effective in
accordance with its terms.

      6. MISCELLANEOUS.

            6.1 Entire Agreement; Amendments. This Guaranty, together with the
other Loan Documents, constitute the entire agreement between the parties with
respect to the subject matter hereof and may not be amended or supplemented
except by a writing signed by each of the Guarantors and the Agent.

            6.2 Headings. The headings in this Guaranty are for convenience of
reference only and are not part of the substance of this Guaranty.

            6.3 Severability. In the event that any one or more of the
provisions contained in this Guaranty shall be determined to be invalid, illegal
or unenforceable in any respect for any reason, the validity, legality and
enforceability of any such provision or provisions in every other respect and
the remaining provisions of this Guaranty shall not be in any way impaired.


                                       7
<PAGE>

            6.4 Notices. Whenever it is provided herein that any notice, demand,
request, consent, approval, declaration or other communication shall or may be
given to or served upon any of the parties by another, or whenever any of the
parties desires to give or serve upon another any such communication with
respect to this Guaranty, each such notice, demand, request, consent, approval,
declaration or other communication shall be in writing and shall be delivered in
person with receipt acknowledged, delivered by reputable overnight courier or
telecopied and confirmed immediately in writing by a copy mailed by registered
or certified mail, return receipt requested, postage prepaid, addressed as
hereinafter set forth, or mailed by registered or certified mail, return receipt
requested, postage prepaid, addressed as follows:

            (a)   If to the Agent, at

                  Pensioenfonds PGGM
                  Kroostweg-Noord 149
                  Zeist, The Netherlands
                  Telecopier:  011-31-30-696-3388
                  Attention:  Mr. Jan van der Vlist
                              Ms. Anneke C. van de Puttelaar

            with a copy to:

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

            (b) If to the Guarantors:

                  Charlotte Office Tower Associates
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:  (212) 605-7199
                  Attention:  Mr. John S. Moody

                  Bryce Mountain, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:  (212) 605-7199
                  Attention:  Mr. John S. Moody


                                       8
<PAGE>

                  DIHC Properties I, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier: (212) 605-7199
                  Attention:  Mr. John S. Moody

                  Dearborn Interests
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:  (212) 605-7199
                  Attention:  Mr. John S. Moody

                  CStone-Oakbrook, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:  (212) 605-7199
                  Attention:  Mr. John S. Moody

                  CStone-527 Madison, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:  (212) 605-7199
                  Attention:  Mr. John S. Moody

                        -- and --

                  Cornerstone Properties Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:  (212) 605-7199
                  Attention:  Mr. John S. Moody

            with a copy to:

                  King & Spalding
                  191 Peachtree Street
                  Atlanta, Georgia  30303
                  Telecopier:  (404) 572-5148
                  Attention:  William B. Fryer, Esq.

or at such other address as may be substituted by notice given as herein
provided. The giving of any notice required hereunder may be waived in writing
by the party entitled to receive such notice. Every notice, demand, request,
consent, approval, declaration or other communication hereunder

                                       9
<PAGE>

shall be deemed to have been duly given or served on the date on which
personally delivered, with receipt acknowledged, on the date of telecopier
transmission, on the date of delivery by reputable overnight courier or three
(3) Business Days after the same shall have been deposited with the United
States mail.

            6.5 Binding Effect. This Guaranty shall bind each of the Guarantors
and shall inure to the benefit of the Agent, the Lenders and their respective
successors and assigns. The Guarantors may not assign this Guaranty without the
consent of the Agent and the Required Lenders.

            6.6 Non-Waiver. The failure of the Agent or any Lender to enforce
any right or remedy hereunder, or promptly to enforce any such right or remedy,
shall not constitute a waiver thereof, nor give rise to any estoppel against the
Agent or any Lender, nor excuse any of the Guarantors from its obligations
hereunder.

            6.7 CHOICE OF LAW. THE TERMS OF THIS GUARANTY SHALL BE GOVERNED BY,
AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF
NEW YORK (EXCLUSIVE OF ANY RULES AS TO CONFLICT OF LAWS) AND THE LAWS OF THE
UNITED STATES APPLICABLE THEREIN. SERVICE OF PROCESS ON EACH OF THE GUARANTORS
IN ANY ACTION ARISING OUT OF OR RELATING TO THIS GUARANTY SHALL BE EFFECTIVE IF
MAILED TO THE GUARANTOR IN ACCORDANCE WITH SECTION 6.4 HEREOF. NOTHING HEREIN
SHALL PRECLUDE THE AGENT OR ANY LENDER FROM BRINGING SUIT OR TAKING OTHER LEGAL
ACTION IN ANY OTHER JURISDICTION.

            6.8 Expenses. Each of the Guarantors agrees that, with or without
notice or demand, it will reimburse the Agent and any Lender for all reasonable
expenses (including counsel fees) actually incurred by the Agent and any Lender
in connection with the enforcement of this Guaranty.

            6.9 Indemnity. Each of the Guarantors agrees to indemnify the Agent
and any Lender and hold them harmless against any documentary taxes, withholding
taxes, assessments or charges made by any governmental authority by reason of
the execution, delivery and performance of this Guaranty.

            6.10 Counterparts. This Guaranty may be executed in any number of
counterparts which shall individually and collectively constitute one agreement.



                                       10
<PAGE>

            IN WITNESS WHEREOF, each of the Guarantors has executed and
delivered this Guaranty as of the date first above written.


                                    CHARLOTTE OFFICE TOWER ASSOCIATES,
                                    a North Carolina general partnership

                                    By:   Its general partner,
                                          Balsam Mountain, Inc.,
                                          a Georgia corporation

                                          By:___________________________________
                                             Name:______________________________
                                             Title:_____________________________


                                                         [SEAL]


                                    By:   Its general partner,
                                          Charlotte Plaza Properties, Inc.,
                                          a Georgia corporation

                                          By:___________________________________
                                             Name:______________________________
                                             Title:_____________________________


                                     [SEAL]


                                    BRYCE MOUNTAIN, INC., a Georgia corporation

                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                        [CORPORATE SEAL]




                                       11
<PAGE>

                                    DIHC PROPERTIES I, INC., a Georgia
                                    corporation

                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                             [CORPORATE SEAL]

                                    DEARBORN INTERESTS,
                                    a Georgia general partnership

                                    By:   Its general partner,
                                          DIHC Dearborn Properties, Inc.,
                                          a Georgia corporation

                                          By:___________________________________
                                             Name:______________________________
                                             Title:_____________________________

                                             [CORPORATE SEAL]

                                    By:   Its general partner,
                                          DIHC Dearborn Venture,
                                          a Georgia general partnership

                                          By:   Its general partner,
                                                DIHC Dearborn Properties, Inc.,
                                                a Georgia corporation

                                          By:___________________________________
                                             Name:______________________________
                                             Title:_____________________________

                                                [CORPORATE SEAL]

                                       12
<PAGE>

                                       By:   Its general partner,
                                             DIHC Marble Place Properties, Inc.,
                                             a Georgia corporation

                                          By:___________________________________
                                             Name:______________________________
                                             Title:_____________________________


                                                [CORPORATE SEAL]


                                    CSTONE-OAKBROOK, INC.,
                                    a Delaware corporation

                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                [CORPORATE SEAL]


                                    CSTONE-527 MADISON, INC.,
                                    a Delaware corporation

                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                      [CORPORATE SEAL]

                                       13
<PAGE>

                              NON-RECOURSE GUARANTY

            GUARANTY, dated as of October _, 1997, of the undersigned, CHARLOTTE
PLAZA PROPERTIES, INC., a Georgia corporation ("Charlotte Plaza"), BALSAM
MOUNTAIN, INC., a Georgia corporation ("Balsam"), DIHC OF GEORGIA, INC., a
Georgia corporation ("DIHC"), DIHC MARBLE PLACE PROPERTIES, INC., a Georgia
corporation ("Marble"), DIHC DEARBORN PROPERTIES, INC., a Georgia corporation
("Dearborn"), DIHC DEARBORN VENTURE, a Georgia general partnership ("Venture")
(collectively referred to herein as "Guarantors") in favor of STICHTING
PENSIOENFONDS VOOR DE GEZONDHEID, GEESTELIJKE EN MAATSCHAPPELIJKE BELANGEN, a
foundation formed according to the laws of The Netherlands, as administrative
agent for the holders of the Notes (as defined below) ("Agent").

                              W I T N E S S E T H:

            WHEREAS, Cornerstone Properties Inc., a Nevada corporation (the
"Borrower") and certain of its subsidiaries, have executed and delivered to the
Agent that certain Note and Collateral Agency Agreement (the "Loan Agreement")
as amended, supplemented or modified from time to time, dated as of the date
hereof pursuant to which Borrower will execute and deliver that certain Deferred
Purchase Price Note (Note A) dated as of the date hereof in the original
principal amount of $55,000,000 ("Note A"), that certain Deferred Purchase Price
Note (Note B) dated as of the date hereof in the original principal amount of
$10,000,000 ("Note B"), that certain Deferred Purchase Price Note (Note C) dated
as of the date hereof in the original principal amount of $30,000,000 ("Note
C"), and that certain Deferred Purchase Price Note (Note E) dated as of the date
hereof in the original principal amount of $120,000,000 ("Note E"), and
CStone-527 Madison, Inc. ("Madison Avenue") will execute and deliver that
certain Deferred Purchase Price Note (Note D) dated as of the date hereof in the
original principal amount of $35,000,000 ("Note D") (Note A, Note B, Note C,
Note D and Note E, as amended, supplemented, replaced, exchanged or modified
from time to time, are collectively referred to herein as the "Notes").

            WHEREAS, Borrower directly or indirectly owns 100% of the equity
interests of each of the Guarantors and Guarantors will derive direct and
indirect economic benefits from the execution and delivery of the Loan Agreement
and the Notes and the transactions related thereto;

            WHEREAS, each of the Guarantors has secured this Guaranty by the
pledge of its rights in and to certain assets, as more fully described in the
Collateral Agreements.

            NOW, THEREFORE, in consideration of the premises and the covenants
hereinafter contained, and to induce the Lenders to accept the Notes, it is
agreed as follows:

            1. DEFINITIONS. Capitalized terms used herein shall have the
meanings assigned to them in the Loan Agreement, unless the context otherwise
requires or unless otherwise defined herein.



<PAGE>

            References to this "Guaranty" shall mean this Guaranty, including
all amendments, modifications and supplements and any exhibits or schedules to
any of the foregoing, and shall refer to the Guaranty as the same may be in
effect at the time such reference becomes operative.

            References to "Guaranteed Obligations" shall mean the unpaid
principal of and interest on the Notes and all other obligations and liabilities
of the Borrower, Madison Avenue and the Guarantors to the Agent and the Lenders
(including, without limitation, interest accruing at the then applicable rate
provided in the Notes after maturity of the Notes and interest accruing at the
then applicable rate provided in the Notes after the filing of any petition in
bankruptcy, or the commencement of any insolvency, reorganization or like
proceeding, relating to the Borrower or Madison Avenue, whether or not a claim
for post-filing or post-petition interest is allowed in such proceeding),
whether direct or indirect, absolute or contingent, due or to become due, or now
existing or hereafter incurred, which may arise under, out of, or in connection
with, this Agreement or any other Loan Document.

            References to "Loan Documents" shall mean the Notes, the Loan
Agreement, and the Collateral Agreements.

            References to "Pledged Collateral" shall mean with respect to
Charlotte Plaza, the Collateral owned by Charlotte Plaza; with respect to
Balsam, the Collateral owned by Balsam, with respect to DIHC Georgia, the
Collateral owned by DIHC Georgia; with respect to Marble, the Collateral owned
by Marble; with respect to Dearborn, the Collateral owned by Dearborn and with
respect to Venture, the Collateral owned by Venture.

            References to "Recourse Guaranty" shall mean that certain Recourse
Guaranty dated the date hereof from Charlotte Office Tower Associates, Bryce
Mountain, Inc., DIHC Properties I, Inc., Dearborn Interests, CStone-Oakbrook,
Inc. and CStone-527 Madison, Inc. in favor of the Agent for the benefit of the
Lenders, as amended, supplemented or modified from time to time.

            2. THE GUARANTY. The guaranty of each of the Guarantors hereunder is
as follows:

            2.1 Guaranty of the Notes. Each of the Guarantors hereby
unconditionally guarantees to the Agent, and its successors, endorsees,
transferees and assigns, for its benefit and for the benefit of the holders of
the Notes, the prompt payment (whether at stated maturity, by acceleration or
otherwise) and performance when due of the Guaranteed Obligations. Each of the
Guarantors agrees that this Guaranty is a guaranty of payment and performance
and not of collection, and that its obligations under this Guaranty shall be
primary, absolute and unconditional, irrespective of, and unaffected by:

            (a) the genuineness, validity, regularity, enforceability or any
      future amendment of, or change in this Guaranty, the Loan Agreement, any
      other Loan Document or any other

                                       2
<PAGE>

      agreement, document or instrument to which Borrower, Madison Avenue and/or
      any of the Guarantors is or are or may become a party;

            (b) the absence of any action to enforce this Guaranty, the Loan
      Agreement, the Notes or any other Loan Document or the waiver or consent
      by the Agent or any Lenders with respect to any of the provisions thereof,

            (c) the existence, value or condition of, or failure to perfect its
      Lien against, any security for the Guaranteed Obligations or any action,
      or the absence of any action, by the Agent or Lenders in respect thereof
      (including, without limitation, the release of any such security); or

            (d) any other action or circumstances which might otherwise
      constitute a legal or equitable discharge or defense of a surety or
      guarantor,

it being agreed by each of the Guarantors that, except as set forth in Section
2.2 hereof, its obligations under this Guaranty shall not be discharged until
the payment and performance, in full, of the Guaranteed Obligations. Each of the
Guarantors shall be regarded, and shall be in the same position, as principal
debtor with respect to the Notes.

            2.2 Termination of Guaranty. Notwithstanding anything to the
contrary contained herein, (a) any and all liability or obligation of Charlotte
Plaza and Balsam hereunder shall terminate and be discharged in full upon
payment and performance, in full, of Note A, provided, however, no Default or
Event of Default shall have occurred and be continuing at the time of such
termination or discharge unless such Default or Event of Default shall cease to
exist as a result of such termination or discharge; (b) any and all liability or
obligation of Dearborn, Marble and Venture hereunder shall terminate and be
discharged in full upon payment and performance, in full, of Note B, provided,
however, no Default or Event of Default shall have occurred and be continuing at
the time of such termination or discharge unless such Default or Event of
Default shall cease to exist as a result of such termination or discharge; and
(c) any and all liability or obligation of DIHC Georgia hereunder shall
terminate and be discharged in full upon payment and performance, in full, of
Note E, provided, however, no Default or Event of Default shall have occurred
and be continuing at the time of such termination or discharge unless such
Default or Event of Default shall cease to exist as a result of such termination
or discharge.

            2.3 Enforcement of Guaranty. In no event shall the Agent or any
Lender have any obligation (although it is entitled, at its option) to proceed
against the Borrower or any other person or any real or personal property
pledged to secure the Guaranteed Obligations before proceeding against any of
the Guarantors, and the Agent or any Lender may proceed, prior or subsequent to,
or simultaneously with, the enforcement of the Agent's or any Lender's rights
hereunder, to exercise any right or remedy which it may have against any
property, real or personal, as a result of any Lien it may have as security for
all or any portion of the Guaranteed Obligations.


                                       3
<PAGE>

            2.4 Waiver. In addition to the waivers contained in Section 2.1
hereof, each of the Guarantors waives, and agrees that it shall not at any time
insist upon, plead or in any manner whatever claim or take the benefit or
advantage of, any appraisal, valuation, stay, extension, marshalling of assets
or redemption laws, or exemption, whether now or at any time hereafter in force,
which may delay, prevent or otherwise affect the performance by the Guarantor of
its obligations under, or the enforcement by Agent or any Lender of, this
Guaranty. Each of the Guarantors hereby waives diligence, presentment and demand
(whether for nonpayment or protest or of acceptance, maturity, extension of
time, change in nature or form of the Notes, the Loan Agreement, or any other
Loan Document, acceptance of further security, release of further security,
composition or agreement arrived at as to the amount of, or the terms of, the
Loan Agreement, the Notes or any other Loan Document, notice of adverse change
in Borrower's or Madison Avenue's financial condition or any other fact which
might materially increase the risk to the Guarantor) with respect to the
Guaranteed Obligations or all other demands whatsoever and waives the benefit of
all provisions of law which are or might be in conflict with the terms of this
Guaranty. Each of the Guarantors represents, warrants and agrees that, as of the
date of this Guaranty, its obligations under this Guaranty are not subject to
any offense or defense against the Agent, any Lender, Madison Avenue or Borrower
of any kind.

            2.5 Benefits of Guaranty. The provisions of this Guaranty are for
the benefit of the Agent, the Lenders and their respective successors,
transferees, endorsees and assigns, and nothing herein contained shall impair,
as between Borrower, Madison Avenue, the Agent and the Lenders, the obligations
of Borrower or Madison Avenue under the Notes, the Loan Agreement or any other
Loan Document.

            2.6 Modification of Note, etc. If the Agent or any Lender shall at
any time or from time to time, with or without the consent of, the Guarantors:

            (a) change or extend the manner, place or terms of payment of, or
      renew or alter all or any portion of, the Notes, the Loan Agreement or any
      other Loan Document;

            (b) take any action under or in respect of the Loan Agreement, the
      Notes or any other Loan Document in the exercise of any remedy, power or
      privilege contained therein or available to it at law, equity or
      otherwise, or waive or refrain from exercising any such remedies, powers
      or privileges;

            (c) amend or modify, in any manner whatsoever, Note D, the Loan
      Agreement or any other Loan Document;

            (d) extend or waive the time for any of the Guarantor's, Borrower's
      or other person's performance of, or compliance with, any term, covenant
      or agreement on its part to be performed or observed under Note D, the
      Loan Agreement or any other Loan Document, or waive such performance or
      compliance or consent to a failure of, or departure from, such performance
      or compliance;

                                       4
<PAGE>

            (e) take and hold security or collateral for the Guaranteed
      Obligations or sell, exchange, release, dispose of, or otherwise deal
      with, any property pledged, mortgaged or conveyed, or in which the Agent
      or any Lender has been granted a Lien, to secure any indebtedness of any
      of the Guarantors, Madison Avenue or Borrower to the Agent or any Lender;

            (f) release anyone who may be liable in any manner for the payment
      of any amounts owed by any of the Guarantors, Madison Avenue or Borrower
      to the Agent or any Lender;

            (g) modify or terminate the terms of any intercreditor or
      subordination agreement pursuant to which claims of other creditors of any
      of the Guarantors, Madison Avenue or Borrower are subordinated to the
      claims of the Agent or any Lender; and/or

            (h) apply any sums by whomever paid or however realized to any
      amounts owing by any of the Guarantors, Madison Avenue or Borrower to the
      Agent or any Lender in such manner as the Agent or any Lender shall
      determine in their discretion;

then neither the Agent nor any Lender shall incur any liability to the Guarantor
pursuant hereto as a result thereof, and no such action shall impair or release
the obligations of any of the Guarantor under this Guaranty.

            2.7 Reinstatement. This Guaranty shall remain in full force and
effect and continue to be effective in the event any petition be filed by or
against Borrower, Madison Avenue or any Guarantor, for liquidation or
reorganization, in the event Borrower, Madison Avenue or any of the Guarantors
becomes insolvent or makes an assignment for the benefit of creditors or in the
event a receiver or trustee be appointed for all or any significant part of
Borrower, Madison Avenue's or Guarantor's assets, and shall continue to be
effective or be reinstated, as the case may be, if at any time payment and
performance of the Guaranteed Obligations, or any part thereof, is, pursuant to
applicable law, rescinded or reduced in amount, or must otherwise be restored or
returned by the Agent or any Lender, whether as a "voidable preference",
"fraudulent conveyance", or otherwise, all as though such payment or performance
had not been made. In the event that any payment, or any part thereof, is
rescinded, reduced, restored or returned, the Guaranteed Obligations shall be
reinstated and deemed reduced only by such amount paid and not so rescinded,
reduced, restored or returned.

            2.8 Election of Remedies, Etc. Any election of remedies which
results in the denial or impairment of the right of the Agent or any Lender to
seek a deficiency judgment against Borrower or Madison Avenue shall not impair
the obligation of any of the Guarantors to pay the full amount of the Guaranteed
Obligations. In the event the Agent or any Lender shall bid at any foreclosure
or trustee's sale or at any private sale permitted by law, the Agent or any
Lender may bid all or less than the amount of the Guaranteed Obligations and the
amount of such bid need not be paid by the Agent or any Lender but shall be
credited against the Guaranteed Obligations. The

                                       5
<PAGE>

amount of the successful bid at any such sale, whether the Agent, any Lender or
any other party is the successful bidder, shall be conclusively deemed to be the
fair market value of the collateral.

            2.9 Continuing Guaranty. The Guarantor agrees that this Guaranty is
a continuing guaranty and shall remain in full force and effect until the
payment in full of all Guaranteed Obligations except as set forth in Section
2.2.

            3. REPRESENTATIONS AND WARRANTIES. Each of the Guarantors makes the
following representations and warranties to the Agent and each Lender:

            3.1 Corporate Power: Authorization; Enforceability. The execution,
delivery and performance of this Guaranty by the Guarantor will not violate any
law or regulation, or any order or decree of any court or governmental
instrumentality, will not conflict with or result in the breach of, or
constitute a default under any indenture, mortgage, deed of trust, lease,
agreement or other instrument to which the Guarantor is a party or by which
Guarantor or any of its property is bound, will not result in the creation or
imposition of any Lien upon any of the property of Guarantor and the same do not
require the consent or approval of any governmental body, agency, authority or
any other person except those already obtained. This Guaranty has been duly
executed and delivered by or on behalf of Guarantor.

            3.2 Affirmation of Covenants, Representations and Warranties.
Guarantor affirms and ratifies the covenants, representations and warranties
contained in Articles III and IV of the Loan Agreement and agrees and covenants
that it shall comply with the terms of such covenants, representations and
warranties.

            4. PERMITTED ASSIGNMENT. The Agent or any Lender may freely assign
its rights and delegate its duties under this Guaranty, but no such assignment
or delegation shall increase or diminish the obligations of the Guarantors
hereunder.

            5. FURTHER ASSURANCES. Each of the Guarantors agrees, upon the
written request of the Agent, to execute and deliver to the Agent, from time to
time, any additional instruments or documents reasonably considered necessary by
the Agent to cause this Guaranty to be, become or remain valid and effective in
accordance with its terms.

            6. NON-RECOURSE. Except as specifically provided for in this Section
6 and in Section 8.11 of the Loan Agreement, (i) neither Guarantors nor any of
their respective officers, directors, shareholders, agents, employees or
representatives (collectively, the "Exculpated Parties") shall be personally
liable for the payment of any sums due hereunder or the performance of any
obligations of the Guarantors hereunder, or under the other Loan Documents, and
(ii) no judgment for the repayment of the Guaranteed Obligations or interest
thereon or any other amount payable pursuant to any of the Loan Documents will
be enforced against any of the Exculpated Parties personally, or any property of
any of the Exculpated Parties other than Collateral and any other security now
or hereafter expressly granted under the Loan Documents in any action to

                                       6
<PAGE>

enforce this Guaranty or otherwise realize upon any security now or hereafter
expressly granted under the Loan Documents or to collect any amount payable
hereunder. Notwithstanding the foregoing:

            Nothing herein contained shall be construed as prohibiting Agent or
any Lender from exercising any and all remedies which the Loan Documents permit,
including the right to bring actions or proceedings against any Guarantor and
other Exculpated Parties and to enter a judgment against any Guarantor and other
Exculpated Parties, so long as the exercise of any remedy does not extend to
execution against or recovery out of any property of any Guarantor or any other
Exculpated Party other than the Collateral expressly granted under the Loan
Documents.

            7. MISCELLANEOUS.

            7.1 Entire Agreement; Amendments. This Guaranty, together with the
other Loan Documents, constitute the entire agreement between the parties with
respect to the subject matter hereof and may not be amended or supplemented
except by a writing signed by the Guarantors and the Agent.

            7.2 Headings. The headings in this Guaranty are for convenience of
reference only and are not part of the substance of this Guaranty.

            7.3 Severability. In the event that any one or more of the
provisions contained in this Guaranty shall be determined to be invalid, illegal
or unenforceable in any respect for any reason, the validity, legality and
enforceability of any such provision or provisions in every other respect and
the remaining provisions of this Guaranty shall not be in any way impaired.

            7.4 Notices. Whenever it is provided herein that any notice, demand,
request, consent, approval, declaration or other communication shall or may be
given to or served upon any of the parties by another, or whenever any of the
parties desires to give or serve upon another any such communication with
respect to this Guaranty, each such notice, demand, request, consent, approval,
declaration or other communication shall be in writing and shall be delivered in
person with receipt acknowledged, delivered by reputable overnight courier or
telecopied and confirmed immediately in writing by a copy mailed by registered
or certified mail, return receipt requested, postage prepaid, addressed as
hereinafter set forth, or mailed by registered or certified mail, return receipt
requested, postage prepaid, addressed as follows:

            (a)   If to the Agent, at

                  Pensioenfonds PGGM
                  Kroostweg-Noord 149
                  Zeist, The Netherlands
                  Telecopier:011-31-30-696-3388
                  Attention: Mr. Jan van der Vlist
                             Ms. Anneke C. van de Puttelaar

                                       7
<PAGE>

            with a copy to:

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

            (b) If to Guarantors:

                  Charlotte Plaza Properties, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:(212) 605-7199
                  Attention: Mr. John S. Moody

                  Balsam Mountain, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:(212) 605-7199
                  Attention: Mr. John S. Moody

                  DIHC of Georgia, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:(212) 605-7199
                  Attention: Mr. John S. Moody


                  DIHC Marble Place Properties, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:(212) 605-7199
                  Attention: Mr. John S. Moody

                  DIHC Dearborn Properties, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:(212) 605-7199
                  Attention: Mr. John S. Moody

                                       8
<PAGE>

                  DIHC Dearborn Venture
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:(212) 605-7199
                  Attention: Mr. John S. Moody

                  -- and --

                  Cornerstone Properties Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:(212) 605-7199
                  Attention: Mr. John S. Moody

            with a copy to:

                  King & Spalding
                  191 Peachtree Street
                  Atlanta, Georgia   30303
                  Telecopier:(404) 572-5148
                  Attention: William B. Fryer, Esq.

or at such other address as may be substituted by notice given as herein
provided. The giving of any notice required hereunder may be waived in writing
by the party entitled to receive such notice. Every notice, demand, request,
consent, approval, declaration or other communication hereunder shall be deemed
to have been duly given or served on the date on which personally delivered,
with receipt acknowledged, on the date of telecopier transmission, on the date
of delivery by reputable overnight courier or three (3) Business Days after the
same shall have been deposited with the United States mail.

            7.5 Binding Effect. This Guaranty shall bind each of the Guarantors
and shall inure to the benefit of the Agent, the Lenders and their respective
successors and assigns. The Guarantors may not assign this Guaranty without the
consent of the Agent and the Required Lenders.

            7.6 Non-Waiver. The failure of the Agent or any Lender to enforce
any right or remedy hereunder, or promptly to enforce any such right or remedy,
shall not constitute a waiver thereof, nor give rise to any estoppel against the
Agent or any Lender, nor excuse any Of the Guarantors from its obligations
hereunder.

            7.7 CHOICE OF LAW. THE TERMS OF THIS GUARANTY SHALL BE GOVERNED BY,
AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE

                                       9
<PAGE>

WITH, THE LAWS OF THE STATE OF NEW YORK (EXCLUSIVE OF ANY RULES AS TO CONFLICT
OF LAWS) AND THE LAWS OF THE UNITED STATES APPLICABLE THEREIN. SERVICE OF
PROCESS ON EACH OF THE GUARANTORS IN ANY ACTION ARISING OUT OF OR RELATING TO
THIS GUARANTY SHALL BE EFFECTIVE IF MAILED TO THE GUARANTOR IN ACCORDANCE WITH
SECTION 7.4 HEREOF. NOTHING HEREIN SHALL PRECLUDE THE AGENT OR ANY LENDER FROM
BRINGING SUIT OR TAKING OTHER LEGAL ACTION IN ANY OTHER JURISDICTION.

            7.8 Expenses. Each of the Guarantors agrees that, with or without
notice or demand, it will reimburse the Agent and any Lender for all reasonable
expenses (including counsel fees) actually incurred by the Agent and any Lender
in connection with the enforcement of this Guaranty.

            7.9 Indemnity. Each of the Guarantors agrees to indemnify the Agent
and any Lender and hold them harmless against any documentary taxes, withholding
taxes, assessments or charges made by any governmental authority by reason of
the execution, delivery and performance of this Guaranty.

            7.10 Counterparts. This Guaranty may be executed in any number of
counterparts which shall individually and collectively constitute one agreement.



                                       10
<PAGE>

            IN WITNESS WHEREOF, each of the Guarantors has executed and
delivered this Guaranty as of the date first above written.

                                    CHARLOTTE PLAZA PROPERTIES, INC.,
                                    a Georgia corporation


                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                [CORPORATE SEAL]


                                    BALSAM MOUNTAIN, INC.,
                                    a Georgia corporation


                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                [CORPORATE SEAL]


                                    DIHC OF GEORGIA, INC.,
                                    a Georgia corporation


                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                [CORPORATE SEAL]



                                       11
<PAGE>

                                    DIHC MARBLE PLACE PROPERTIES, INC.,
                                    a Georgia corporation


                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                [CORPORATE SEAL]


                                    DIHC DEARBORN PROPERTIES, INC.,
                                    a Georgia corporation


                                    By:___________________________________
                                       Name:______________________________
                                       Title:_____________________________

                                                [CORPORATE SEAL]


                                    DIHC DEARBORN VENTURE
                                    By:   Its general partner,
                                          DIHC Marble Place Properties, Inc.,
                                          a Georgia corporation

                                          By:___________________________________
                                             Name:______________________________
                                             Title:_____________________________

                                                [CORPORATE SEAL]

                                    By:   Its general partner,
                                          DIHC Dearborn Properties I, Inc.,
                                          a Georgia corporation

                                          By:___________________________________
                                             Name:______________________________
                                             Title:_____________________________

                                                [CORPORATE SEAL]


                                       12
<PAGE>

                              NON-RECOURSE GUARANTY
                          (Cornerstone Properties Inc.)

            GUARANTY, dated as of October -, 1997, of the undersigned,
CORNERSTONE PROPERTIES INC., a Nevada corporation ("Guarantor" or "Borrower"),
in favor of STICHTING PENSIOENFONDS VOOR DE GEZONDHEID, GEESTELIJKE EN
MAATSCHAPPELIJKE BELANGEN, a foundation formed according to the laws of The
Netherlands, as administrative agent under the Loan Agreement for the holders of
the Notes (as defined below) ("Agent").

                              W I T N E S S E T H :

            WHEREAS, Guarantor and certain of its subsidiaries, have executed
and delivered to the Agent that certain Note and Collateral Agency Agreement
(the "Loan Agreement") as amended, supplemented or modified from time to time,
dated as of the date hereof pursuant to which Borrower will execute and deliver
that certain Deferred Purchase Price Note (Note A) dated as of the date hereof
in the original principal amount of $55,000,000 ("Note A"), that certain
Deferred Purchase Price Note (Note B) dated as of the date hereof in the
original principal amount of $10,000,000 ("Note B "), that certain Deferred
Purchase Price Note (Note C) dated as of the date hereof in the original
principal amount of $30,000,000 ("Note C"), and that certain Deferred Purchase
Price Note (Note E) dated as of the date hereof in the original principal amount
of $120,000,000 ("Note E"), and CStone-527 Madison, Inc. ("Madison Avenue") will
execute and deliver that certain Deferred Purchase Price Note (Note D) dated as
of the date hereof in the original principal amount of $35,000,000 ("Note D")
(Note A, Note B, Note C, Note D and Note E, as amended, supplemented, replaced,
exchanged or modified from time to time, are collectively referred to herein as
the "Notes").

            WHEREAS, Guarantor directly or indirectly owns 100% of the equity
interests of Madison Avenue and will derive direct and indirect economic
benefits from the execution and delivery of the Loan Agreement and the
transactions related thereto;

            WHEREAS, Guarantor has secured this Guaranty by the pledge of its
rights in and to the stock of Madison Avenue.

            NOW, THEREFORE, in consideration of the premises and the covenants
hereinafter contained, and to induce the Lenders to accept the Notes, it is
agreed as follows:

            1. DEFINITIONS. Capitalized terms used herein shall have the
meanings assigned to them in the Loan Agreement, unless the context otherwise
requires or unless otherwise defined herein.

            References to this "Guaranty" shall mean this Guaranty, including
all amendments, modifications and supplements and any exhibits or schedules to
any of the foregoing, and shall refer to the Guaranty as the same mav be in
effect at the time such reference becomes operative.
<PAGE>

            References to "Guaranteed Obligations" shall mean the unpaid
principal of and interest on Note D and all other obligations and liabilities of
Madison Avenue and the Guarantor to the Agent and the Lenders (including,
without limitation, interest accruing at the then applicable rate provided in
the Notes after maturity of the Notes and interest accruing at the then
applicable rate provided in the Notes after the filing of any petition in
bankruptcy, or the commencement of any insolvency, reorganization or like
proceeding, relating to Madison Avenue, whether or not a claim for post-filing
or post-petition interest is allowed in such proceeding), whether direct or
indirect, absolute or contingent, due or to become due, or now existing or
hereafter incurred, which may arise under, out of, or in connection with, this
Agreement or any other Loan Document.

            References to "Loan Documents" shall mean the Notes, the Loan
Agreement, and the Collateral Agreements.

            References to "Pledged Collateral" shall mean the Collateral owned
by Guarantor.

            2. THE GUARANTY. The guaranty of the Guarantor hereunder is as
follows:

            2.1 Guaranty of Note D. The Guarantor hereby unconditionally
guarantees to the Agent, and its successors, endorsees, transferees and assigns,
for its benefit and for the benefit of the holders of the Notes, the prompt
payment (whether at stated maturity, by acceleration or otherwise) and
performance when due of the Guaranteed Obligations. The Guarantor agrees that
this Guaranty is a guaranty of payment and performance and not of collection,
and that its obligations under this Guaranty shall be primary, absolute and
unconditional, irrespective of, and unaffected by:

            (a) the genuineness, validity, regularity, enforceability or any
      future amendment of, or change in this Guaranty, the Loan Agreement, any
      other Loan Document or any other agreement, document or instrument to
      which Madison Avenue and/or the Guarantor is or are or may become a party;

            (b) the absence of any action to enforce this Guaranty, the Loan
      Agreement, Note D or any other Loan Document or the waiver or consent by
      the Agent or any Lenders with respect to any of the provisions thereof,

            (c) the existence, value or condition of, or failure to perfect its
      Lien against, any security for the Guaranteed Obligations or any action,
      or the absence of any action, by the Agent or Lenders in respect thereof
      (including, without limitation, the release of any such security); or

            (d) any other action or circumstances which might otherwise
      constitute a legal or equitable discharge or defense of a surety or
      guarantor,


                                       2
<PAGE>

it being agreed by the Guarantor that, except as set forth in Section 2.2
hereof, its obligations under this Guaranty shall not be discharged until the
payment and performance, in full, of the Guaranteed Obligations. The Guarantor
shall be regarded, and shall be in the same position, as principal debtor with
respect to Note D.

            2.2 Termination of Guaranty. Notwithstanding anything to the
contrary contained herein, any and all liability or obligation of Guarantor
hereunder shall terminate and be discharged in full upon payment and
performance, in full, of Note D, provided, however, no Default or Event of
Default shall have occurred and be continuing at the time of such termination or
discharge unless such Event of Default shall cease to exist as a result of the
termination or discharge.

            2.3 Enforcement of Guaranty. In no event shall the Agent or any
Lender have any obligation (although it is entitled, at its option) to proceed
against Madison Avenue or any other person or any real or personal property
pledged to secure the Guaranteed Obligations before proceeding against the
Guarantor, and the Agent or any Lender may proceed, prior or subsequent to, or
simultaneously with, the enforcement of the Agent's or any Lender's rights
hereunder, to exercise any right or remedy which it may have against any
property, real or personal, as a result of any Lien it may have as security for
all or any portion of the Guaranteed Obligations.

            2.4 Waiver. In addition to the waivers contained in Section 2.1
hereof, the Guarantor waives, and agrees that it shall not at any time insist
upon, plead or in any manner whatever claim or take the benefit or advantage of,
any appraisal, valuation, stay, extension, marshalling of assets or redemption
laws, or exemption, whether now or at any time hereafter in force, which may
delay, prevent or otherwise affect the performance by the Guarantor of its
obligations under, or the enforcement by Agent or any Lender of, this Guaranty.
The Guarantor hereby waives diligence, presentment and demand (whether for
nonpayment or protest or of acceptance, maturity, extension of time, change in
nature or form of the Notes, the Loan Agreement, or any other Loan Document,
acceptance of further security, release of further security, composition or
agreement arrived at as to the amount of, or the terms of, the Loan Agreement,
Note D or any other Loan Document, notice of adverse change in Madison Avenue's
financial condition or any other fact which might materially increase the risk
to the Guarantor) with respect to the Guaranteed Obligations or all other
demands whatsoever and waives the benefit of all provisions of law which are or
might be in conflict with the terms of this Guaranty. The Guarantor represents,
warrants and agrees that, as of the date of this Guaranty, its obligations under
this Guaranty are not subject to any offense or defense against the Agent, any
Lender or Madison Avenue of any kind.

            2.5 Benefits of Guaranty. The provisions of this Guaranty are for
the benefit of the Agent, the Lenders and their respective successors,
transferees, endorsees and assigns, and nothing herein contained shall impair,
as between Madison Avenue, the Agent and the Lenders, the obligations of Madison
Avenue under Note D, the Loan Agreement or any other Loan Document.


                                       3
<PAGE>

            2.6 Modification of Note, etc. If the Agent or any Lender shall at
any time or from time to time, with or without the consent of, the Guarantor:

            (a) change or extend the manner, place or terms of payment of, or
      renew or alter all or any portion of, Note D, the Loan Agreement or any
      other Loan Document;

            (b) take any action under or in respect of the Loan Agreement, Note
      D or any other Loan Document in the exercise of any remedy, power or
      privilege contained therein or available to it at law, equity or
      otherwise, or waive or refrain from exercising any such remedies, powers
      or privileges;

            (c) amend or modify, in any manner whatsoever, Note D, the Loan
      Agreement or any other Loan Document;

            (d) extend or waive the time for any of the Guarantor's, Madison
      Avenue or other person's performance of, or compliance with, any term,
      covenant or agreement on its part to be performed or observed under Note
      D, the Loan Agreement or any other Loan Document, or waive such
      performance or compliance or consent to a failure of, or departure from,
      such performance or compliance:

            (e) take and hold security or collateral for the Guaranteed
      Obligations or sell, exchange, release, dispose of, or otherwise deal
      with, any property pledged, mortgaged or conveyed, or in which the Agent
      or any Lender has been granted a Lien, to secure any indebtedness of any
      of the Guarantor or Madison Avenue to the Agent or any Lender;

            (f) release anyone who may be liable in any mariner for the payment
      of any amounts owed by any of the Guarantor or Madison Avenue to the Agent
      or any Lender;

            (g) modify or terminate the terms of any intercreditor or
      subordination agreement pursuant to which claims of other creditors of the
      Guarantor or Madison Avenue are subordinated to the claims of the Agent or
      any Lender; and/or

            (h) apply any sums by whomever paid or however realized to any
      amounts owing by the Guarantor or Madison Avenue to the Agent or any
      Lender in such manner as the Agent or any Lender shall determine in their
      discretion;

then neither the Agent nor any Lender shall incur any liability to the Guarantor
pursuant hereto as a result thereof, and no such action shall impair or release
the obligations of any of the Guarantor under this Guaranty.

            2.7 Reinstatement. This Guaranty shall remain in full force and
effect and continue to be effective in the event any petition be filed by or
against Madison Avenue or Guarantor for liquidation or reorganization, in the
event Madison Avenue or the Guarantor

                                       4
<PAGE>

becomes insolvent or makes an assignment for the benefit of creditors or in the
event a receiver or trustee be appointed for all or any significant part of
Madison Avenue's or Guarantor's assets, and shall continue to be effective or be
reinstated, as the case may be, if at any time payment and performance of the
Guaranteed Obligations, or any part thereof, is, pursuant to applicable law,
rescinded or reduced in amount, or must otherwise be restored or returned by the
Agent or any Lender, whether as a "voidable preference", "fraudulent
conveyance", or otherwise, all as though such payment or performance had not
been made. In the event that any payment, or any part thereof, is rescinded,
reduced, restored or returned, the Guaranteed Obligations shall be reinstated
and deemed reduced only by such amount paid and not so rescinded, reduced,
restored or returned.

            2.8 Election of Remedies, Etc. Any election of remedies which
results in the denial or impairment of the right of the Agent or any Lender to
seek a deficiency judgment against Madison Avenue shall not impair the
obligation of the Guarantor to pay the full amount of the Guaranteed
Obligations. In the event the Agent or any Lender shall bid at any foreclosure
or trustee's sale or at any private sale permitted by law, the Agent or any
Lender may bid all or less than the amount of the Guaranteed Obligations and the
amount of such bid need not be paid by the Agent or any Lender but shall be
credited against the Guaranteed Obligations. The amount of the successful bid at
any such sale, whether the Agent, any Lender or any other party is the
successful bidder, shall be conclusively deemed to be the fair market value of
the collateral.

            2.9 Continuing Guaranty. The Guarantor agrees that this Guaranty is
a continuing guaranty and shall remain in full force and effect until the
payment in full of all Guaranteed Obligations except as set forth in Section
2.2.

            3. REPRESENTATIONS AND WARRANTIES. The Guarantor makes the following
representations and warranties to the Agent and each Lender:

            3.1 Corporate Power; Authorization; Enforceability. The execution,
delivery and performance of this Guaranty by the Guarantor will not violate any
law or regulation, or any order or decree of any court or governmental
instrumentality, will not conflict with or result in the breach of, or
constitute a default under any indenture, mortgage, deed of trust, lease,
agreement or other instrument to which the Guarantor is a party or by which
Guarantor or any of its property is bound, will not result in the creation or
imposition of any Lien upon any of the property of Guarantor and the same do not
require the consent or approval of any governmental body, agency, authority or
any other person except those already obtained. This Guaranty has been duly
executed and delivered by or on behalf of Guarantor.

            3.2 Affirmation of Covenants, Representations and Warranties.
Guarantor affirms and ratifies the covenants, representations and warranties
contained in Articles III, IV and V of the Loan Agreement and agrees and
covenants that it shall comply with the terms of such covenants, representations
and warranties.


                                       5
<PAGE>

            4. PERMITTED ASSIGNMENT. The Agent or any Lender may freely assign
its rights and delegate its duties under this Guaranty, but no such assignment
or delegation shall increase or diminish the obligations of the Guarantor
hereunder.

            5. FURTHER ASSURANCES. The Guarantor agrees, upon the written
request of the Agent, to execute and deliver to the Agent, from time to time,
any additional instruments or documents reasonably considered necessary by the
Agent to cause this Guaranty to be, become or remain valid and effective in
accordance with its terms.

            6. NON-RECOURSE. Except as specifically provided for in this Section
6 and in Section 8.11 of the Loan Agreement, (i) neither Guarantor nor any of
its respective officers, directors, shareholders, agents, employees or
representatives (collectively, the "Exculpated Parties") shall be personally
liable for the payment of any sums due hereunder or the performance of any
obligations of the Guarantor hereunder, or under the other Loan Documents, and
(ii) no judgment for the repayment of the Guaranteed Obligations or interest
thereon or any other amount payable pursuant to any of the Loan Documents will
be enforced against any of the Exculpated Parties personally, or any property of
any of the Exculpated Parties other than Collateral and any other security now
or hereafter expressly granted under the Loan Documents in any action to enforce
this Guaranty Agreement or otherwise realize upon any security now or hereafter
expressly granted under the Loan Documents or to collect any amount payable
hereunder. Notwithstanding the foregoing:

            Nothing herein contained shall be construed as prohibiting Agent or
any Lender from exercising any and all remedies which the Loan Documents permit,
including the right to bring actions or proceedings against Guarantor and other
Exculpated Parties and to enter a judgment against Guarantor and other
Exculpated Parties, so long as the exercise of any remedy does not extend to
execution against or recovery out of any property of Guarantor or any other
Exculpated Party other than the Collateral expressly granted under the Loan
Documents;

            7. MISCELLANEOUS.

            7.1 Entire Agreement; Amendments. This Guaranty, together with the
other Loan Documents, constitute the entire agreement between the parties with
respect to the subject matter hereof and may not be amended or supplemented
except by a writing signed by the Guarantor and the Agent.

            7.2 Headings. The headings in this Guaranty are for convenience of
reference only and are not part of the substance of this Guaranty.

            7.3 Severability. In the event that any one or more of the
provisions contained in this Guaranty shall be determined to be invalid, illegal
or unenforceable in any respect for any reason, the validity, legality and
enforceability of any such provision or provisions in every other respect and
the remaining provisions of this Guaranty shall not be in any way impaired.

                                       6
<PAGE>

            7.4 Notices. Whenever it is provided herein that any notice, demand,
request, consent, approval, declaration or other communication shall or may be
given to or served upon any of the parties by another, or whenever any of the
parties desires to give or serve upon another any such communication with
respect to this Guaranty, each such notice, demand, request, consent, approval,
declaration or other communication shall be in writing and shall be delivered in
person with receipt acknowledged, delivered by reputable overnight courier or
telecopied and confirmed immediately in writing by a copy mailed by registered
or certified mail, return receipt requested, postage prepaid, addressed as
hereinafter set forth, or mailed by registered or certified mail, return receipt
requested, postage prepaid, addressed as follows:

            (a)   If to the Agent, at

                  Pensioenfonds PGGM
                  Kroostweg-Noord 149
                  Zeist, The Netherlands
                  Telecopier:  01 1-31-30-696-3388
                  Attention:    Mr. Jan van der Vlist
                                Ms. Anneke C. van de Puttelaar

            with a copy to:

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

            (b) If to the Guarantor:

                  Charlotte Plaza Properties, Inc.
                  126 East 56th Street
                  New York, New York  10022
                  Telecopier:  (212) 605-7199
                  Attention:    Mr. John S. Moody

            with a copy to:

                  King & Spalding
                  191 Peachtree Street
                  Atlanta, Georgia  30303
                  Telecopier:  (404) 572-5148
                  Attention:    William B. Fryer, Esq.


                                       7
<PAGE>

or at such other address as may be substituted by notice given as herein
provided. The giving of any notice required hereunder may be waived in writing
by the party entitled to receive such notice. Every notice, demand, request,
consent, approval, declaration or other communication hereunder shall be deemed
to have been duly given or served on the date on which personally delivered,
with receipt acknowledged, on the date of telecopier transmission, on the date
of delivery by reputable overnight courier or three (3) Business Days after the
same shall have been deposited with the United States mail.

            7.5 Binding Effect. This Guaranty shall bind the Guarantor and shall
inure to the benefit of the Agent, the Lenders and their respective successors
and assigns. The Guarantor may not assign this Guaranty without the consent of
the Agent and the Required Lenders.

            7.6 Non-Waiver. The failure of the Agent or any Lender to enforce
any right or remedy hereunder, or promptly to enforce any such right or remedy,
shall not constitute a waiver thereof, nor give rise to any estoppel against the
Agent or any Lender, nor excuse the Guarantor from its obligations hereunder.

            7.7 CHOICE OF LAW. THE TERMS OF THIS GUARANTY SHALL BE GOVERNED BY,
AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF
NEW YORK (EXCLUSIVE OF ANY RULES AS TO CONFLICT OF LAWS) AND THE LAWS OF THE
UNITED STATES APPLICABLE THEREIN. SERVICE OF PROCESS ON THE GUARANTOR IN ANY
ACTION ARISING OUT OF OR RELATING TO THIS GUARANTY SHALL BE EFFECTIVE IF MAILED
TO THE GUARANTOR IN ACCORDANCE WITH SECTION 7.4 HEREOF. NOTHING HEREIN SHALL
PRECLUDE THE AGENT OR ANY LENDER FROM BRINGING SUIT OR TAKING OTHER LEGAL ACTION
IN ANY OTHER JURISDICTION.

            7.8 Expenses. The Guarantor agrees that, with or without notice or
demand, it will reimburse the Agent and any Lender for all reasonable expenses
(including counsel fees) actually incurred by the Agent and any Lender in
connection with the enforcement of this Guaranty.

            7.9 Indemnity. Except as provided in Section __ of the Loan
Agreement, the Guarantor agrees to indemnify the Agent and any Lender and hold
them harmless against any documentary taxes, withholding taxes, assessments or
charges made by any governmental authority by reason of the execution, delivery
and performance of this Guaranty.

            7.10 Counterparts. This Guaranty may be executed in any number of
counterparts which shall individually and collectively constitute one agreement.



                                       8
<PAGE>

            IN WITNESS WHEREOF, the Guarantor has executed and delivered this
Guaranty as of the date first above written.

                                    CORNERSTONE PROPERTIES INC.,
                                    a Nevada corporation

                                    By:__________________________________
                                         John S. Moody
                                         President and Chief Executive Officer

                                    By:__________________________________
                                         Rodney C. Dimock
                                         Executive Vice President and
                                         Chief Operating Officer

                                          [CORPORATE SEAL]

                                       9
<PAGE>

                                  SCHEDULE 3.5

                               EXISTING DEFAULTS