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                                                                    EXHIBIT 10.8

                         AGREEMENT OF PURCHASE AND SALE

     THIS AGREEMENT OF PURCHASE AND SALE (hereinafter referred to as the
"Agreement"), made this 25th day of April, 2006, by and between FOULGER LAND
LIMITED PARTNERSHIP, a Virginia limited partnership ("FLLP"), ARGO ORCHARD RIDGE
MANAGER, INC., a Maryland corporation and ARGO INVESTMENT COMPANY, LC, a
Maryland limited liability company (the "Argo Sellers") (FLLP and the Argo
Sellers are sometimes herein collectively herein referred to as "Seller") and
COLUMBIA EQUITY TRUST, INC., a Maryland corporation (hereinafter referred to as
"Purchaser").

                                    RECITALS:

     R.1. The Argo Sellers are the sole members of Argo Orchard Ridge, LLC, a
Maryland limited liability company ("Argo"), and own one hundred percent (100%)
of the limited liability company membership interests (the "Argo Membership
Interests") in Argo.

     R.4. FLLP and Argo (collectively herein referred to as "Owner"), as tenants
in common, pursuant to the terms of that certain Tenants-in-Common Agreement,
dated (the "TIC Agreement") own certain real property located in Gaithersburg,
Montgomery County, Maryland, having an address of 101 Orchard Ridge Drive,
Gaithersburg, Maryland, and as more particularly described on EXHIBIT A attached
hereto; together with all right, title and interest of Seller in and to all
easements, rights, privileges, rights-of-way, hereditaments, tenements and
appurtenances belonging to the land, all right, title and interest in and to all
open or proposed highways, streets, roads, avenues, alleys, easements, strips,
gores and rights of way, in, on, across, in front of, contiguous to, abutting or
adjoining the land (hereinafter collectively with the land referred to as the
"Real Property"), and together with all improvements situate thereon, including
an approximately 102,396 square foot office building and all appurtenances owned
by Seller and applicable thereto (the "Improvements").

     R.5. Owner also owns certain personal property used or useable in
conjunction with the Real Property and Improvements, including all personal
property located on or at the Real Property or Improvements as of the date
hereof (provided the same is not owned by tenants occupying space in the
Improvements pursuant to the leases as hereafter defined), including that
personal property as more particularly described on EXHIBIT B attached hereto
and made a part hereof (hereinafter referred to as the "Personal Property").

     R.6. Owner also owns certain intangible property used or useable in
connection with the Real Property, Improvements and Personal Property,
including, but not limited to, Owner's rights in and to certain trade names,
licenses, permits, authorizations and goodwill used in connection with any part
of the Real Property and Improvements; Owner's rights in and to all leases,
subleases, and other rental agreements which grant a possessory interest in and
to any space in the Improvements, including the Leases; Owner's interest, if
any, in and to any and all licenses, permits, guarantees and warranties now in
effect with respect to the Real Property,

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Improvement and Personal Property; all written or oral contracts or agreements
binding on Owner or the Property (all such contracts in effect as of the date
hereof being described on EXHIBIT C attached hereto and made a part hereof and
being hereinafter collectively referred to as the "Contracts") in effect at
Settlement (as hereafter defined) in any way relating to the Real Property; and
all prepaid rents, security, damage, lease and/or other deposits established in
connection with the Property and currently held by Owner (collectively, the
"Intangible and Other Property") (the Real Property, Improvements, Personal
Property, Contracts, Leases (as such leases are identified on EXHIBIT D attached
hereto and made a part hereof, the "Leases"), and Intangible and Other Property
are sometimes collectively referred to herein as the "Property").

     R.7. Purchaser desires to purchase from Seller and Seller desires to sell
to Purchaser, the FLLP Membership Interests (as hereafter defined) and the Argo
Membership Interests, in accordance with the terms and conditions hereinafter
set forth.

     NOW, THEREFORE, in consideration of the mutual promises of the parties
hereto, made one to another, and for other good and valuable consideration, the
receipt and sufficiency of which is hereby acknowledged, the parties hereto
agree as follows:

     1. Agreement of Purchase and Sale. Seller hereby agrees to sell and convey
the FLLP Membership Interests (as herein defined) and the Argo Membership
Interests to Purchaser, and Purchaser hereby agrees to purchase the FLLP
Membership Interests and the Argo Membership Interests from Seller, in
accordance with the terms and provisions hereof.

     2. Title and Survey. At Settlement, Argo and the LLC shall hold marketable
fee simple title to the Property of record and in fact, which shall be insurable
at standard rates by Commonwealth Land Title Insurance Company (the "Title
Insurer"), excepting only the following permitted exceptions (the "Permitted
Exceptions"):

          A. The lien of real estate taxes not yet due and payable;

          B. All applicable codes, regulations, ordinances and other
restrictions of any governmental or quasi-governmental authority (including any
zoning authority) having jurisdiction over the Property; and

          C. Such other matters as are set forth on Purchaser's Title Commitment
and Survey to which Purchaser does not object as hereinafter set forth.

     Prior to the expiration of the Feasibility Study Period (as hereafter
defined), Purchaser shall (i) cause the Title Insurer to cause title to the
Property to be inspected and to issue to Purchaser a commitment for title
insurance (the "Title Commitment"), together with all documents referred to in
the Title Commitment, including without limitation, deeds, lien instruments,
plats, restrictions, easements, UCC financing statement searches, and judgment
searches (collectively, the "Title Documents"), and (ii) at its option, cause a
licensed surveyor to prepare a current ALTA survey of the Property (the
"Survey"). In the event the Title Commitment or Survey discloses encumbrances on
title to the Property which are unacceptable to Purchaser, Purchaser shall give
notice thereof (in accordance with the terms hereof) to Seller not later than
five (5) days prior to the expiration of the Feasibility Study Period (which
notice


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shall enclose a copy of the Title Commitment, Title Documents and Survey)
specifying the objections of Purchaser (the "Title Objections"). Seller shall
have the option, but not the obligation, exercised by notice to Purchaser not
later than the business day immediately preceding the expiration of the
Feasibility Study Period, to cure the Title Objections (or any of them) at
Seller's own expense to the reasonable satisfaction of Purchaser, or not to cure
one or more Title Objections. A failure of Seller to timely give such notice
shall be deemed Seller's election not to cure any Title Objections. In the event
Seller elects to cure the Title Objections, the time specified for Settlement
shall be extended for the period necessary for such cure, not to exceed thirty
(30) days. If Seller elects not to cure all Title Objections, then (i) the
Deposit (as hereafter defined) shall be returned to Purchaser, and (ii) this
Agreement shall be null and void, and neither party shall have any further
right, liability or obligation hereunder except for Purchaser's indemnification
obligation pursuant to Section 9 hereof which shall survive any such
termination; provided, however, that Purchaser may elect, by written notice to
Seller given not later than the earlier of five (5) business days of receipt of
Seller's notice (or deemed notice) of its election not to cure all Title
Objections, or the final day of the Feasibility Study Period, to waive such of
the Title Objections as Seller has elected not to cure, in which event the
parties shall proceed with Settlement in accordance with the terms hereof
(provided that the foregoing cure period shall remain applicable to any Title
Objections which Seller has elected to attempt to cure), with no abatement in
the Purchase Price. In the event Purchaser does not terminate this Agreement in
accordance with Section 9 hereof, the same shall be deemed Purchaser's election
to waive such Title Objections. In the event Seller elects to cure some or all
Title Objections, but has been unable to effectuate such cure to the reasonable
satisfaction of Purchaser by that date which is thirty (30) days after the date
otherwise set forth for Settlement, then Purchaser shall have the right, within
five (5) business days after such thirty (30) day period, to (i) waive the
uncured Title Objections and proceed to Settlement in accordance with the terms
hereof, with no abatement in the Purchase Price, or (ii) to terminate this
Agreement, upon which the Deposit shall be returned to Purchaser and neither
party shall have any further right or liability hereunder, other than those
obligations which expressly survive the termination of this Agreement. The
foregoing notwithstanding, Seller shall remove or cause to be removed, at or
prior to Settlement hereunder, any monetary lien created by or at the direction
of Seller.

     3. Purchase Price. The purchase price ("Purchase Price") for the FLLP
Membership Interests and the Argo Membership Interests is Twenty Seven Million
Four Hundred Forty Thousand Dollars ($27,440,000.00), which shall be as set
forth below.

     The Purchase Price shall be paid by (i) assumption by Purchaser of Owner's
outstanding debt on the Property as discussed below, and (ii) delivery by
Purchaser to Seller of the balance of the Purchase Price which shall be paid by
federal wire transfer of immediately available funds to be received by Seller
not later than 2:00 p.m. Eastern Time on the Settlement Date.

     The debt to which the Property is currently subject is that certain loan
(the "Loan") extended by UBS Real Estate Investments, Inc. ("UBS"), originally
in the principal amount of $15,500,000.00. Purchaser shall promptly make
application to UBS and diligently pursue in good faith, approval of the
transactions contemplated by this Agreement. Seller shall be solely responsible
for the payment of the assumption/transfer fee to UBS, as well as any and all
other fees and expenses charged by or on behalf of UBS (including attorneys'
fees) in connection with such assumption (or attempted assumption). Purchaser
shall diligently and in good faith


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cooperate with Seller and UBS in connection with obtaining UBS' approval of the
transactions contemplated by this Agreement, including, but not limited to,
promptly supplying all information requested by UBS, financial or otherwise,
necessary therefor, and providing to UBS an acceptable substitute non-recourse
carveout guarantor(s) in the place and stead of those originally set forth in
the Loan. It shall be a condition precedent to Seller's and Purchaser's
obligation to consummate Settlement hereunder that UBS approve the transactions
contemplated by this Agreement, including the Owner entering into the Nextone
Lease (as hereinafter defined) and the Harvey Cleary Lease (as hereinafter
defined) and the associated buy-out of the Heller Ehrman lease (collectively,
the "Lease Transactions"). In the event UBS does not, despite Purchaser's good
faith efforts, approve the transactions contemplated by this Agreement, this
Agreement shall terminate, the Deposit shall be returned to Purchaser and
neither party shall thereafter have any further right or obligation hereunder
other than Purchaser's indemnification obligations hereunder which shall survive
such termination.

     4. Deposit.

          A. Simultaneously with the execution hereof by all parties hereto,
Purchaser shall deliver to the Title Insurer, as escrow agent, an initial
deposit of Seven Hundred Fifty Thousand Dollars ($750,000.00) (the "Initial
Deposit"). Upon the expiration of the Feasibility Study Period, provided
Purchaser has not timely terminated this Agreement, Purchaser shall deliver to
the Title Insurer an additional deposit in the amount of Two Hundred Fifty
Thousand Dollars ($250,000.00) (the "Additional Deposit"). As used herein the
term "Deposit" shall mean the Initial Deposit, the Additional Deposit, and all
accrued interest in the Escrow Account. The Deposit shall be held in escrow by
the Title Insurer in an interest-bearing escrow account (the "Escrow Account")
accruing to the benefit of the party entitled to the Deposit in accordance with
the provisions hereof, such escrow account to be maintained at a federally
insured financial institution. All interest earned on the escrow account shall
be charged to the account of Purchaser for federal income tax purposes, and, in
connection therewith, Purchaser represents that its federal taxpayer
identification number is 20-1978579.

          B. The Title Insurer shall deliver the Deposit held hereunder (a) to
or at the direction of Purchaser concurrent with the Settlement, provided
Purchaser shall pay the full Purchase Price to Seller (or at Purchaser's
direction to be applied against the Purchase Price at Settlement), or (b) at
such other time, before or after Settlement, to Purchaser or Seller, as such
party becomes entitled to the Deposit as provided in this Agreement.

          C. If this escrow shall be involved in any litigation or controversy,
the parties hereto shall severally hold the Title Insurer free and harmless
against any cost or expense that may be suffered by it by reason of such
litigation or controversy, other than due to its negligence or malfeasance. All
such costs and expenses shall be paid by the party who does not prevail in such
litigation. In addition, the party who prevails shall be indemnified against any
cost or expense, including reasonable attorneys' fees (both at trial and on
appeal), and replacement of any depletion in the escrow funds, if such funds are
ultimately to be paid to the prevailing party.

          D. In the event conflicting demands are made, or notices served, upon
the Title Insurer with respect to this escrow, the Title Insurer shall have,
without limitation, the following rights and obligations:


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               (i) Withhold and stop all further proceedings in, and performance
of this escrow for a reasonable period of time to permit resolution; or

               (ii) File a suit in interpleader and obtain an order from a court
of competent jurisdiction requiring the parties to interplead and litigate in
such court their several claims and rights amongst themselves. In the event such
interpleader suit is brought, and the escrow funds paid and/or delivered into
court, the Title Insurer shall ipso facto be fully released and discharged from
all obligations to perform any and all duties or obligations relative to such
funds which are imposed upon it by this Agreement.

          E. The Title Insurer, in its capacity as escrow agent, is not to be
held liable for the sufficiency or correctness of the form, manner of execution
or validity of any instrument that might be deposited into the escrow, nor as to
the identity, authority or rights of any person executing the same, nor the
failure of any other party to comply with any provisions of any agreement,
contract or other instrument filed herein, and its duties hereunder shall be
limited to the safekeeping of the money, instruments, or other documents
received by it, and for the disposition of the same in accordance with the
provisions of this Agreement, and for the discharge of its obligations specified
in this Agreement.

          F. Prior to the earlier of the Settlement or the termination of this
Agreement in accordance with its terms, neither party shall have the right to
withdraw any instruments or monies deposited by them with the Title Insurer,
except as herein specifically provided.

     5. Settlement. The consummation of the purchase and sale of the FLLP
Membership Interests and the Argo Membership Interests ("Settlement") shall take
place on the date that is thirty (30) days after the expiration of the
Feasibility Study Period (the "Settlement Date"), time being of the essence;
provided, however, that Purchaser shall have the right to postpone the
Settlement Date for thirty (30) days in order to obtain the consent of UBS to
the transactions contemplated by this Agreement, including the Lease
Transactions. Settlement shall occur at such place in the Washington, DC
metropolitan area as is acceptable to Purchaser and Seller.

     6. Pre-Settlement and Settlement Obligations.

          A. Immediately prior to Settlement, Seller (or the applicable Seller,
as set forth below) shall:

               (i) FLLP shall form a single member limited liability company
under the laws of the State of Maryland (the "LLC");

               (ii) FLLP shall transfer FLLP's ownership interest in the
Property (subject to the TIC Agreement) to the LLC by deed in a form reasonably
acceptable to Purchaser;

               (iii) The Argo Sellers shall form a limited liability company
under the laws of the State of Maryland (the "Argo MI Holder" and, together with
the LLC, the "Pass-Through Entities"); and


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               (iv) The Argo Sellers shall execute and deliver an assignment of
the Argo Membership Interests to Argo MI Holder and cause Argo MI Holder to
execute an assumption of the Argo Membership Interests, both in forms reasonably
acceptable to Purchaser.

          B. At Settlement, Seller shall:

               (i) Cause FLLP to execute and deliver an assignment of one
hundred percent (100%) of the membership interests in the LLC (the "FLLP
Membership Interests") to Purchaser's designee in a form reasonably acceptable
to Purchaser;

               (ii) Cause Argo MI Holder to execute and deliver an assignment of
the Argo Membership Interests to Purchaser in a form reasonably acceptable to
Purchaser;

               (iii) Deliver to Purchaser copies (and originals where in the
possession or control of Seller) of all available books, records, plans,
studies, data, reports and other materials in Seller's possession or control
relating to or in connection with the Property;

               (iv) Deliver to Purchaser the originals of the Leases (to the
extent in Seller's possession or control) and other agreements executed with
each tenant and all other letters, memoranda and all other records related to
the Leases or tenants;

               (v) Deliver all security deposits and other escrows in Seller's
possession, if any, of tenants occupying space in the Property pursuant to the
Leases as of the date of Settlement;

               (vi) Give full and complete possession of the Property to
Purchaser, not subject to the right of possession by any person or entity other
than the tenants pursuant to the Leases and otherwise pursuant to the Permitted
Exceptions;

               (vii) Deliver to Purchaser copies (and originals where in the
possession of Seller) of all warranties, guarantees, licenses, permits, and
certificates of occupancy which exist for or in respect to the Property;

               (viii) Deliver to Purchaser an affidavit in a form acceptable to
Purchaser and as prescribed in the Foreign Investment in Real Property Transfer
Act of the Internal Revenue Code and the regulations promulgated thereon
("FIRPTA") which certifies that each Seller is not a "foreign person" as defined
therein;

               (ix) Confirm in writing that the representations and warranties
of Seller made in Section 20 remain true and correct as of the Settlement Date;

               (x) Deliver to Purchaser all keys to the Property in Seller's
possession;

               (xi) Provide to Purchaser in Excel format by quarter, the detail
general ledgers and trial balances for the Property for the fiscal year prior to
the closing date and for the interim period from the most recent fiscal year
through the Settlement Date; and


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               (xii) Execute and deliver any and all other documents reasonably
required of Seller to consummate the transaction contemplated hereby.

          C. At Settlement, Purchaser shall:

               (i) Deliver or cause to be delivered to Seller the Purchase
Price, as adjusted pursuant to Section 7 hereof;

               (ii) Execute and deliver an assumption of the FLLP Membership
Interests from FLLP in a form reasonably acceptable to Seller;

               (iii) Execute and deliver an assumption of the Argo Membership
Interests in a form reasonably acceptable to Seller; and

               (iv) Execute any and all other documents reasonably required of
Purchaser to consummate the transaction contemplated hereby.

     7. Adjustments. For purposes of calculating prorations, Purchaser shall be
deemed to be in title to the Property, and therefore entitled to the income
therefrom and responsible for the expenses thereof, for the entire day upon
which Settlement occurs. All such prorations shall be made on the basis of the
actual number of days of the year and month that shall have elapsed as of the
Settlement Date. The amount of such prorations shall be adjusted in cash after
Settlement, as and when complete and accurate information becomes available.
Seller and Purchaser agree to cooperate and use their good faith and diligent
efforts to make such adjustments within a reasonable time after the calendar
year end following Settlement. Except as specifically provided otherwise herein,
items of income and expense for the period prior to the Settlement Date will be
for the account of Seller and items of income and expense for the period on and
after the Settlement Date will be for the account of Purchaser, all as
determined by the accrual method of accounting. Bills received after Settlement
that relate to expenses incurred, services performed or other amounts allocable
to the period prior to the Settlement Date shall be paid by Purchaser if such
bills are for Operating Expense Pass-Throughs (as hereinafter defined). The
obligations of the parties pursuant to this Section 7 shall survive Settlement
and shall not merge into any documents of conveyance delivered at Settlement.

          A. REAL ESTATE TAXES AND SPECIAL ASSESSMENTS. Real estate taxes and
assessments imposed by governmental authority (and any assessments imposed by
private covenant) due and payable in the year of Settlement shall be prorated as
of the Settlement Date based upon the most recent tax bills or assessment.
Seller shall receive a credit for any taxes and assessments paid by Owner and
applicable to any period after Settlement. Special assessments shall be prorated
according to the due dates of installments, with Seller being responsible for
installments that become due and payable before the Settlement Date, and
Purchaser being responsible for installments that become due and payable on or
after the Settlement Date. If, for the fiscal tax year in which Settlement is
held, or any prior year, there are any tax protests filed, or abatement
application proceedings pending at any time prior to Settlement with reference
to the Property, Seller shall have the right to settle such protests or
proceedings as long as such settlement does not include any agreement as to the
valuation of the Property for real estate tax purposes for the period after
Settlement. Otherwise, Seller shall not settle the same without


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Purchaser's prior written consent. All amounts recovered as a result thereof,
whether by settlement or otherwise, shall, net of attorneys' fees and other
expenses, be apportioned as of Settlement for the fiscal tax year in which
Settlement is held, and paid, when received, to the parties entitled thereto;
provided, however, that to the extent any such amounts are payable to Tenant
pursuant to the terms of the Leases, such amounts shall be promptly paid over to
such Tenant. The parties agree to execute any papers or take such steps, either
before or after any Settlement, as may be necessary to carry out the intention
of the foregoing.

          B. TITLE INSURANCE. Purchaser shall pay all title examination fees of
Title Insurer, the premium for the cost of the Title Insurance Policy with
endorsements and all costs of any lender's title insurance policy, if
applicable.

          C. SURVEY COSTS. Purchaser shall pay all costs of the survey.

          D. SETTLEMENT FEE. Seller and Purchaser will each pay one-half of any
reasonable and customary closing fee charged by the Title Insurer.

          E. TRANSFER TAX. Neither party shall have any obligation for the
payment of any transfer or recordation taxes.

          F. COLLECTED RENTS. All collected net rent (excluding Operating
Expense Pass-Throughs) and other collected income under the Leases shall be
prorated as of Settlement. Seller shall be charged with any rent and other
income collected before Settlement but applicable to any period of time after
Settlement. Uncollected rent and other income shall not be prorated. Purchaser
shall apply rent and other income from Tenants that are collected by Purchaser
after Settlement in the following order: (i) first, to Purchaser's reasonable
third party costs of collection incurred with respect to such Tenant, (ii)
second, to Purchaser in payment of the current rent due under such Lease, (iii)
third, to Purchaser in payment of delinquent rent due under such Leases for the
period from and after Settlement, and (iv) fourth, to Seller in payment of rent
coming due and payable prior to Settlement. Any prepaid rents for the period on
or following the Settlement Date shall be paid over by Seller to Purchaser.
Purchaser will make commercially reasonable efforts, without suit, to collect
any rents relating to the period before Settlement. Seller shall not have the
right to sue delinquent Tenants for delinquent rent after Settlement.

          G. OPERATING EXPENSE PASS-THROUGHS. Owner, as landlord under the
Leases, is currently collecting from Tenants under the Leases additional rent
over an expense stop to cover taxes, insurance, utilities, common area
maintenance and other operating costs and expenses (collectively, "Operating
Expense Pass-Throughs") in connection with the ownership, operation, maintenance
and management of the Property. Seller and Purchaser shall each receive a debit
or credit, as the case may be, for the difference between the Tenants' collected
account balance for Operating Expense Pass-Throughs and the amount of Operating
Expense Pass-Throughs due to or from Tenants as of the Settlement Date.
Operating Expense Pass-Throughs for Seller's period of ownership shall be
reasonably estimated by the parties if final bills are not available. If Owner
was overpaid by any Tenant for the period with respect to any such charges prior
to Settlement, Seller shall remit to Purchaser such estimated overpayment at
Settlement. If Owner was underpaid by any Tenant for the period with respect to
any such charges prior to


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Settlement, Seller shall receive a credit at Settlement for the amount of such
estimated underpayment. Any item in this Section 7(g) that is paid directly by
any Tenant pursuant to its Leases shall not be prorated between the parties, and
Purchaser shall look to said Tenant to pay such items. Seller and Purchaser
agree to cooperate and use their good faith and diligent efforts to do a true-up
and make any necessary adjustments to the proration of the Operating Expense
Pass-Throughs within ninety (90) days after the calendar year end following
Settlement.

          H. SECURITY DEPOSITS. Purchaser shall receive a credit against the
Purchase Price in an amount equal to the sum of all unapplied cash security
deposits paid by any Tenant plus, if accrued interest on such security deposits
must be reimbursed to any Tenant that paid a security deposit, all interest
accrued on such security deposits.

          I. INSURANCE. Purchaser hereby acknowledges and agrees that all
insurance maintained on behalf of or with respect to the Owner and the Property
will be terminated as of the Settlement Date.

          J. BANK ACCOUNTS. Seller shall, or shall cause Owner to, close all
bank accounts, lock boxes, other depositories and safe deposit boxes relating to
the Property and all property contained therein, to the extent it relates to the
Property shall be delivered or transferred to the bank accounts, lock boxes,
other depositories and safe deposit boxes designated by Purchaser. Purchaser
shall, or shall cause Owner to, establish new bank accounts, lock boxes, other
depositories and safe deposit boxes, to the extent it deems necessary to operate
the business of the Owner and the Property from and after the Settlement Date.

          K. OTHER COSTS. All other costs shall be allocated in accordance with
the customs prevailing in similar transactions in the Washington, DC
metropolitan area.

     8. Feasibility Study Period.

          A. Seller shall, to the extent it has not previously done so, within
two (2) business days after mutual execution of this Agreement, deliver to
Purchaser the documents listed on EXHIBIT E, to the extent the same are in
Seller's or Owner's possession or control. Purchaser shall have until 5:00 p.m.
Eastern Time on April 21, 2006 (the "Feasibility Study Period"), to complete
certain inspections of the Property (including, without limitation, any
environmental and engineering inspections of the Property). During the
Feasibility Study Period, Purchaser, its agents and representatives shall be
entitled to make such investigations, studies and inspections of the Property as
it deems necessary in order for it to make a determination as to whether the
Property is suitable for its intended purpose, provided that (i) Purchaser shall
only undertake intrusive testing of the Property following notice to and receipt
of written consent from Seller, and (ii) Purchaser shall not contact or disturb
any tenants at or about the Property without Seller's prior written consent and
all such contact with any tenant shall be coordinated through Seller and Seller
shall have the opportunity to be present thereat. In the event Purchaser, in its
sole and absolute discretion, provides Seller with written notice, prior to 5:00
p.m. Eastern Time on the final day of the Feasibility Study Period, of
Purchaser's intention not to proceed to Settlement hereunder, the Title Insurer
shall immediately return the Deposit to Purchaser, this Agreement shall
terminate as of such date, and neither party shall have any further right or
obligation hereunder other than those which by their express terms survive such
termination. In


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the event Purchaser fails to provide notice of termination as aforesaid,
Purchaser shall be deemed to have accepted the Property and the status of title
thereto as of such date, this Agreement shall remain in full force and effect in
accordance with its terms.

          B. Purchaser, its agents and representatives shall have the right
during normal business hours and in coordination with Seller's management agent,
to enter upon the Property prior to Settlement for the purpose of making any
inspection, investigations, studies or tests. Purchaser shall repair any damage
to the Property resulting from any inspections, studies or tests performed by
Purchaser. In connection with such entry onto the Property, Purchaser agrees
that it shall be responsible for any damages to the same resulting from such
operations and shall indemnify and hold Seller harmless from all claims of any
type arising out of or incident to Purchaser's entry onto the Property.
Purchaser's obligations under this Section 8.B. shall survive Settlement or any
other termination of this Agreement. Prior to any entry on the Property,
Purchaser shall deliver to Seller a policy of comprehensive general liability
insurance, with a combined single limit of not less than $2,000,000 per
occurrence, naming Seller and its management agent as additional insureds, and
insuring against loss or damage resulting from Purchaser's entry on the
Property.

          C. Seller agrees that, subsequent to the expiration of the Feasibility
Study Period, provided Purchaser has not terminated this Agreement as set forth
in Section 8.A. above, Seller shall not execute any leases, licenses or other
rental or occupancy agreements for vacant space within the Improvements, without
the prior consent of Purchaser.

          D. The parties acknowledge that Purchaser may be required to perform a
historical audit of the Property in order to comply with Item 3-14 of Regulation
S-X promulgated under the Securities Act of 1933 and the Securities Exchange Act
of 1934. Seller shall, effective with the Settlement Date, make commercially
reasonable efforts to permit Purchaser's auditors access at that location where
Owner customarily maintains its records, upon reasonable advance notice and
during normal business hours, to all of the Property's books and records and the
operating statements (certified by an officer of Seller or of the general
partner of Seller) and property management balance sheets for the Property for
one (1) calendar year prior to the Settlement Date and for the period from the
end of the prior fiscal year through the Settlement Date. To the extent that the
originals or copies of same are not otherwise provided by Seller to Purchaser at
Settlement, and to the extent that the same are ordinarily maintained by Seller
in its normal course of business, such books and records shall include the
detail general ledger of profits and loss, accounts receivable records, rent
rolls, billing records, accounts payable records all contracts. Buyer's access
rights shall commence on the Settlement Date and shall continue until the
successful completion of the audit and the filing of the 3-14 report with the
SEC, written notice of which shall be delivered promptly by Purchaser to Seller.
The foregoing obligation shall fully survive Settlement. Notwithstanding
anything to the contrary in the foregoing, other than providing the access to
Purchaser specified herein, Seller shall not have any liability or
responsibility in connection with or in any manner related to, directly or
indirectly, any audit required to be made by Purchaser or any compliance
required of Purchaser with any Regulation under the Securities Act of 1933 or
the Securities Act of 1934.

     9. Condemnation. In the event Seller or Owner receives notice of any
material condemnation proceedings or notice of the intention of any governmental
or quasi-governmental


                                       10

<PAGE>

authority to initiate condemnation proceedings involving a material portion of
the Property, or if any such proceedings commence, or an actual condemnation or
taking of a material portion of the Property or any portion thereof occurs,
Seller will promptly notify Purchaser and Purchaser may, within fifteen (15)
days thereafter (i) elect to terminate this Agreement, in which event, the
Deposit shall be returned to Purchaser, and the parties shall be relieved of all
further liability hereunder, except those obligations herein that expressly
survive the termination of this Agreement; or (ii) if Purchaser does not elect
to terminate this Agreement the condemnation award as well as any unpaid claims
or rights in connection with such condemnation shall be assigned to Purchaser at
Settlement, or, if paid to Seller prior to Settlement, shall be credited at
Settlement against and up to the amount of the Purchase Price. Provided that the
Feasibility Study Period has expired and Purchaser has given written notice of
its intention to proceed with Settlement hereunder notwithstanding any such
proceeding, Purchaser shall have the right to participate with Seller (all
action after such time until Settlement to be upon mutual agreement of the
parties) in the negotiations and settlement of any condemnation claim.

     10. Casualty Loss. In the event that subsequent to the date hereof any part
of the Property is damaged or destroyed by fire or other casualty and the cost
of repair thereof is in excess of Five Hundred Thousand Dollars ($500,000.00) (a
"Material Casualty"), Seller will promptly notify Purchaser, and Purchaser may,
at its option, by giving written notice to Seller within ten (10) business days
after receipt from Seller of notice of Seller's estimate of restoration of the
Property caused by such casualty, terminate this Agreement. In such event
Purchaser shall be entitled to the return of the Deposit, and thereafter neither
Purchaser nor Seller shall have any further liability to the other hereunder,
except for any obligations herein that expressly survive the termination of this
Agreement. In the event of a casualty which is not a Material Casualty, or in
the event of a Material Casualty as a result of which Purchaser does not elect
to terminate this Agreement, and provided that the Feasibility Study Period has
expired and Purchaser has given written notice of its intention to proceed with
Settlement hereunder, Purchaser shall be obligated to proceed to Settlement in
accordance with this Agreement and all insurance proceeds in connection with
such casualty, plus the amount of Owner's deductible, less such amount as
previously expended by Owner in the repair of such casualty, shall be assigned
to Purchaser at Settlement or, if paid to Owner prior thereto, shall be credited
against the unpaid Purchase Price due at Settlement.

     11. Default.

          A. If Purchaser without cause shall fail or refuse to make Settlement
hereunder, the amount of damages not being ascertainable, the Deposit shall be
forfeited and the same shall forthwith be delivered by the Title Insurer to
Seller as liquidated damages. In the event of such default by Purchaser,
Seller's sole remedy shall be restricted to retention of said Deposit, and
Purchaser shall have no other responsibility or liability of any kind to Seller
by virtue of such default.

          B. If Seller, through no fault of Purchaser, shall fail to perform its
obligations hereunder to make full Settlement in accordance with the terms
hereof, the sole and exclusive remedy of Purchaser shall be either the right to
terminate this Agreement and have the Deposit promptly returned to Purchaser, or
the right to specific performance to enforce Seller's obligation to consummate
Settlement hereunder.


                                       11

<PAGE>

          C. The representations of Seller contained in this Agreement shall
survive Settlement; provided, however, (i) any cause of action of Purchaser
against Seller by reason of a breach or default of any of the representations
set forth herein or in any certificates executed by Seller pursuant to this
Agreement shall automatically expire as of the date which is twelve (12) months
after Settlement (the "Warranty Expiration Date"), except that the same shall
not expire as to any such breach or default as to which Purchaser has given
written notice to Seller of a claim for any such breach or default prior to the
Warranty Expiration Date, (ii) no action shall be brought against Seller as a
result of any alleged breach of a representation or warranty unless and until
the amount at issue as a result thereof (including all such alleged breached in
the aggregate) is in excess of $50,000.00, and (iii) Seller's total liability
for any breach or breaches of its representations set forth herein shall in no
event exceed $1,000,000.00 in the aggregate, which liability limit shall survive
Settlement. The Warranty Expiration Date and the foregoing limitations on
Seller's liability shall be inapplicable to any breach of a Seller's warranty
under or pursuant to Section 13.U. hereof.

          D. In the event of litigation by either party to enforce its rights
hereunder, the prevailing party in any such action shall be entitled to recover
from the other its court costs and reasonable and actual attorneys' fees
incurred in the pursuit of such action.

     12. Broker. Each party, by the execution hereof, represents and warrants
that neither party has engaged the services of any broker, finder, agent or
other person or entity in connection with this transaction other than Advantis
Real Estate Services Company which shall be paid a fee by Seller upon (and only
in the event of) consummation of Settlement hereunder, pursuant to separate
agreement. Each party shall indemnify and hold harmless the other against and
from any loss, cost, damage or fee resulting from any inaccuracy of such
representation and warranty.

     13. Seller's Representations and Warranties. Seller hereby represents and
warrants the following to Purchaser, all of which representations and warranties
shall be true and complete as of Settlement:

          A. AUTHORITY. Each Seller and Pass-Through Entity which is an entity
(as opposed to a natural person) is duly qualified and validly existing in good
standing under the laws of the state of its organization and is (or, in the case
of the Pass-Through Entities, on the Settlement Date, will be) qualified to do
business in the State of Maryland. The execution and delivery of this Agreement
has been, and the performance of each such Seller's and Pass-Through Entity's
obligations hereunder will be, duly authorized by all necessary action on the
part of each Seller and Pass-Through Entity, and this Agreement constitutes the
legal, valid, binding and enforceable obligation of each Seller, subject to
equitable principles and principles governing creditors' rights generally.
Attached to this Agreement as Exhibit K, Exhibit L and Exhibit M are true,
correct and complete copies of (i) the Limited Partnership Agreement of Foulger,
and (ii) the tenancy in common agreement between Foulger and Argo and (iii) the
Operating Agreement of Argo.

          B. FIRPTA. Neither any person or entity constituting Seller, the
Pass-Through Entities nor Owner is a "foreign person," "foreign partnership,"
"foreign trust" or "foreign estate" as those terms are defined in Section 1445
of the Internal Revenue Code.


                                       12

<PAGE>

          C. PROCEEDINGS. To the knowledge of Seller, there is no action,
litigation, investigation, condemnation or proceeding of any kind pending or, to
the knowledge of Seller, threatened against Seller, the Pass-Through Entities or
Owner which would have a material and adverse affect on the ability of Seller to
perform its obligations under this Agreement, or related to the Subject Property
or the Leases other than as disclosed to Purchaser in writing.

          D. LEASES.

               (i) EXHIBIT D is a true and complete list of the Leases and all
other occupancy agreements relating to the Property. Except as set forth in the
Leases, there are no rights of first refusal, options to terminate without cause
of Owner, options to renew, options to purchase, or any rent abatements given to
tenant under the Leases (the "Tenant") after the Tenant is in occupancy and
paying rent.

               (ii) To the Seller's knowledge, each Lease is in full force and
effect according to the terms set forth therein, and there is no modification,
amendment or alteration in writing or otherwise, except as set forth in EXHIBIT
D.

               (iii) To Seller's knowledge there are not, and neither Seller nor
Owner has received written notice from any Tenant of any unperformed obligation
of the Owner, as landlord under any of the Leases, including, without
limitation, failure of the landlord to construct any required tenant
improvements. Neither Seller nor Owner has been advised in writing of any claims
or disputes giving rise to any setoff by Tenant. With respect to the Leases, all
tenant improvement allowances have been paid and all tenant improvements have
been completed. As of the Settlement Date, no Tenant shall be entitled to any
free rent under any Lease.

               (iv) Neither Owner nor any Tenant is in default under the Leases
(beyond any applicable grace or cure period), and there are no rent
delinquencies of more than thirty (30) days.

               (v) There are no brokers' commissions, finders' fees, or other
charges payable or to become payable to any third party on behalf of Seller or
Owner as a result of or in connection with the Leases, including, without
limitation, any unexecuted options to expand or renew, except as set forth on
the rent roll attached as EXHIBIT F (the "Rent Roll").

               (vi) Except as set forth on the Rent Roll, (i) no rent has been
paid by any Tenant more than one month in advance and (ii) no unapplied security
deposits have been paid by any Tenant.

     The foregoing terms and provisions of this subsection 13.D shall be deemed
replaced, and Seller's representations concerning the Leases shall be
terminated, as of such time as an Estoppel Certificate (as herein defined) is
received under and pursuant to each such Lease.

          E. BLOCKED PERSONS. Seller has not received written notice that either
any party constituting Seller, the Pass-Through Entities or Owner is:


                                       13

<PAGE>

               (i) listed on the Specially Designated Nationals and Blocked
Persons List maintained by the Office of Foreign Assets Control, Department of
the Treasury ("OFAC") pursuant to Executive Order No. 13224, 66 Fed. Reg. 49079
Sept. 25, 2001 (the "Order") and/or on any other list of terrorists or terrorist
organizations maintained pursuant to any of the rules and regulations of OFAC or
pursuant to any other applicable Orders (such lists are collectively referred to
as the "Lists");

               (ii) a person who has been determined by competent authority to
be subject to the prohibitions contained in the Order;

               (iii) owned or controlled by, and does not act for or on behalf
of, any person or entity on the Lists or any other person or entity who has been
determined by competent authority to be subject to the prohibitions contained in
the Order.

          F. BANKRUPTCY. Neither any party constituting Seller, the Pass-Through
Entities nor Owner is the subject of, and neither has received any written
notice of or threat that either of them has or will become the subject of, any
reorganization, liquidation, dissolution, receivership or other action or
proceeding under the United States Bankruptcy Code, 11 U.S.C. Sections 101, et
seq., or any other federal, state or local laws affecting the rights of debtors
and/or creditors generally, whether voluntary or involuntary and including,
without limitation, proceedings to set aside or avoid any transfer of any
interest in property or obligations, whether denominated as a fraudulent
conveyance, preferential transfer or otherwise, or to recover the value thereof
or to charge, encumber of impose a lien thereon.

          G. CONTRACTS. EXHIBIT C attached hereto is a complete list of all
current Contracts which list includes the names of the contracting parties, the
dates of the Contracts and a listing of all amendments to such Contracts.

          H. CONDEMNATION. To the best of Seller's knowledge, Seller has no
knowledge of nor has it or Owner received any written notice of any pending or
contemplated condemnation proceedings affecting all or any part of the Property.

          I. ACCURACY OF DOCUMENTS. All documents and records to be delivered
comprising the Property Information are true, correct and complete copies of the
documents and records purported to be delivered thereunder as appear in Seller's
(or Owner's) files as of the date hereof (provided the foregoing is not intended
and shall not be construed to constitute a representation or warranty as to the
accuracy or completeness of the content of any such document prepared by any
third party).

          J. TITLE TO MEMBERSHIP INTERESTS. As of the date hereof, the Argo
Sellers are the record and beneficial owner of all of the Argo Membership
Interests. As of the Settlement Date, Argo MI Holder will be the record and
beneficial owner of all of the Argo Membership Interests and FLLP will be the
record and beneficial owner of all of the FLLP Membership Interests. As of the
Settlement Date, the Argo Membership Interests will constitute 100% of all of
the outstanding membership interests of Argo free and clear of all right, claim
and interest of others. As of the Settlement Date, the FLLP Membership Interests
will constitute


                                       14

<PAGE>

100% of all outstanding partnership interests of the LLC free and clear of all
right, claim and interest of others

          K. LOAN ESCROW ACCOUNTS. Attached hereto as EXHIBIT N is a true and
accurate list of all escrow accounts (and the amount of each such escrow
account) held by UBS in connection with the Loan.

          L. SUBSIDIARIES. Except for the LLC, neither Owner nor the LLC has any
subsidiaries nor any investments or other interests in (including advances to)
any other business, person or venture.

          M. FINANCIAL STATEMENTS. Seller has furnished Purchaser with copies of
the balance sheet of Owner as of January 31, 2006 and the related statement of
earnings for the period ending on such date (hereinafter collectively referred
to as the "Financial Statements"). To the best of Seller's knowledge, the
Financial Statements (a) are in accordance with the books and records of Owner,
(b) present fairly (i) the assets, liabilities and financial condition of Owner
as of such date, and (ii) the results of operations for the period covered
thereby, and (c) have been prepared on a tax basis consistent with that of
preceding years. Since the date of the Financial Statements, there has not been
any material adverse change in the financial condition, business, properties or
results of operations of Owner.

          N. ACTIONS BY OWNER AND LLC SINCE THE DATE OF THE FINANCIAL
STATEMENTS. Since the date of the Financial Statements, unless otherwise
disclosed, neither Owner nor the LLC has:

               (i) incurred or agreed to incur any obligations or liabilities,
except obligations or liabilities in the ordinary course of business, or under
contracts, leases, documents and transactions listed in the attached exhibits or
incurred or agreed to incur any debt;

               (ii) satisfied or discharged any lien, or paid any obligation or
liabilities other than (A) liabilities included in the Financial Statements, (B)
liabilities incurred in the ordinary course of business, and (C) obligations and
liabilities under contracts, leases, transactions or documents listed in the
attached exhibits;

               (iii) mortgaged, pledged or subjected to lien or other
encumbrance any of its property;

               (iv) sold or transferred any of its assets or canceled any debts
owing to it or claims owed by it;

               (v) waived any rights of material value;

               (vi) experienced any material change in the financial condition,
or in the operations or business of Owner, other than changes in the ordinary
course of business; or

               (vii) suffered any damage or destruction, whether or not covered
by insurance, materially and adversely affecting the properties or business of
Owner or the LLC.


                                       15

<PAGE>

          O. LIABILITIES. Neither Owner nor the LLC has any debts, liabilities,
or obligations of, or claims of any kind or character, whether accrued, absolute
or contingent ("Liabilities") other than Liabilities reflected on the Financial
Statements and trade payables incurred in the ordinary course of business and to
be adjusted as provided herein.

          P. COMPLIANCE WITH LEGAL REQUIREMENTS. To the knowledge of Seller,
Owner is in material compliance with all applicable laws, ordinances, rules,
regulations, orders and requirements of all governmental authorities relating
to, or regulating, the activities of Owner.

          Q. CERTAIN PROPERTY OBLIGATIONS. As of the date hereof: (a) all
payments, levies, dues, charges, assessments and other amounts (except for real
estate taxes, special assessments and front foot benefit or private utility
charges not yet due and payable) which are payable on or before the date hereof
affecting the Property ("Title Documents") which, to Seller's knowledge, exist,
are paid in full (except for financings of record and insurance premiums), and
(b) to Seller's Knowledge, there are no existing defaults or violations
affecting the Property or the obligations of the Owner under the Title
Documents.

          R. ALL CONTRACTS. Seller has furnished to Purchaser copies of all
Contracts as are kept in Owner's files in the ordinary course of business.

          S. LITIGATION. There is no action, suit, litigation, judicial
proceeding or governmental investigation (collectively, the "Actions") pending,
or to Seller's Knowledge, threatened, against or relating to the business of
Owner or involving any of its property which, if adversely determined, could
reasonably be expected to have a material adverse effect on Owner or the
Property. Owner does not currently have pending, and is not considering, any
litigation or the pursuit of any rights or remedies that may be available
against any third parties relating to the business of the Owner or involving any
of its property.

          T. TAX MATTERS.

               (i) Owner, the LLC and Seller have filed all Tax Returns required
to be filed by either of them involving Owner or the LLC prior to the date
hereof. To Owner's and Seller's respective knowledge, all such filed Tax Returns
were correct and complete in all material respects and all Taxes owed by or on
behalf of Owner or the LLC (whether or not shown on any Tax Return) have been
paid. To Owner's and Seller's respective knowledge, Owner has complied in all
material respects with all applicable laws, rules and regulations relating to
the payment and withholding of Taxes and Owner or the LLC or Seller, as
appropriate, has withheld and paid over to the proper governmental entities,
within the time period prescribed by law, all material amounts required to be so
withheld and paid over under applicable laws and regulations. Neither Owner nor
the LLC is the beneficiary of any extension of time within which to file a Tax
Return involving Owner or the LLC, except for an extension to July 15, 2006
(which Tax Return shall be filed and all taxes thereunder paid prior to
Settlement). Since the date of such Financial Statements, Owner has not incurred
any material liability for Taxes other than in the ordinary course of business.
To Seller's Knowledge, no event has occurred, and no condition or circumstance
exists, which presents a material risk that any material Tax described in the
preceding sentences will be imposed upon Owner or the LLC.


                                       16

<PAGE>

               (ii) Neither Owner nor the LLC is the subject of any audit,
examination, or other proceeding in respect of Taxes, and Seller has no actual
knowledge that any audit, examination or other proceeding in respect of Taxes
involving Owner or the LLC is being considered by any Tax authority. No
deficiencies for any Taxes have been proposed, asserted or assessed against
Owner or the LLC. Neither Owner, the LLC nor Seller has given any currently
effective waiver of any statute of limitations in respect of Taxes involving
Owner or the LLC or agreed to any currently effective extension of time with
respect to a Tax assessment or deficiency involving Owner or the LLC. There are
no liens (other than for Taxes not yet due and payable) on any of the assets of
Owner or the LLC that arose in connection with any failure (or alleged failure)
to pay any Tax.

               (iii) There is no dispute or claim concerning any Tax liability
involving Owner or the LLC either (A) claimed or raised by any governmental
authority in writing or (B) to the knowledge of Seller, based upon personal
contact with any agent of such authority, which remains unsettled as of the date
hereof.

               (iv) Neither Owner nor the LLC is liable for any Taxes
attributable to any other Person, whether by reason of being a member of an
affiliated group, being a party to a tax sharing agreement, as a transferee or
successor, or otherwise.

               (v) No powers of attorney or other authorizations are in effect
that grant to any Person the authority to represent Owner, the LLC or Seller in
connection with any Tax matter or proceeding involving Owner or the LLC.

               (vi) Owner has delivered to Purchaser correct and complete copies
of any Tax Returns and reports Owner filed for all periods not barred by the
applicable statute of limitations. With respect to periods not barred by the
applicable statute of limitations, Schedule (i) describes all material Tax
elections, consents and agreements made by or affecting Owner or any Person to
whose liabilities Owner has succeeded that will be in effect after the
Settlement Date, (ii) lists all material types of Taxes paid and Tax Returns
filed by or on behalf of Owner or any such Person, (iii) expressly indicates
each Tax with respect to which Owner or any such Person is or has been included
in a consolidated, unitary or combined Tax Return, and (iv) describes the status
of all examinations, administrative or judicial proceedings, and litigation with
respect to any Taxes of Owner or for which it may be liable. The LLC has never
been required to pay taxes or file any tax return.

               (vii) Owner has delivered to Purchaser any depreciation,
amortization, or tax basis information necessary for the preparation of
Purchaser's tax returns.

          U. PRIOR ACTIVITIES OF OWNER AND THE LLC. Neither Owner nor the LLC
has, directly or indirectly, engaged in any business or activity other than
owning the Property and those businesses and activities incidental thereto.

          V. BINDING EFFECT: APPROVALS AND CONSENTS. Subject to approval by UBS
of the transactions contemplated hereby, Seller's execution and delivery of this
Agreement and performance of the transactions contemplated hereby will not
result in a breach or violation by Owner, the Pass-Through Entities or Seller
of, or constitute a default by Owner, the Pass-


                                       17

<PAGE>

Through Entities or Seller under, any agreement or instrument to which Owner,
the Pass-Through Entities or Seller is a party or by which any of its properties
are bound, or the organizational documents of Owner, the Pass-Through Entities
or Seller, or any statute, judgment, order, injunction, decree, regulation or
ruling of any court or other governmental authority.

          W. INSURANCE. Owner currently maintains insurance of the types, in the
amounts and insuring against the risks as set forth in EXHIBIT G. Seller and
Purchaser acknowledge and agree that all policies of insurance currently held by
Owner will be cancelled or Owner will be removed as an insured or beneficiary
thereunder at Settlement.

          X. BANKING RELATIONSHIPS. EXHIBIT H attached hereto lists all bank
accounts of Owner and the persons authorized to make withdrawals therefrom, all
lock boxes and other depositories maintained by or on behalf of Owner and the
persons authorized to make withdrawals therefrom or have access thereto, and all
safe deposit boxes of Owner and the persons authorized to obtain access to such
safe deposit boxes.

          Y. EMPLOYEES. Neither Owner nor the LLC has any employees.

     For purposes of this Section 13, the following capitalized terms shall have
the following meanings:

     "Tax" or "Taxes" shall mean any federal, state, local or foreign income,
gross receipts, license, payroll, employment, excise, severance, stamp,
occupation, premium, windfall profits, environmental (including taxes under Code
Section 59A), customs duties, capital stock, franchise, profits, withholding,
social security (or similar), unemployment, disability, real property, real
estate taxes, personal property, sales, use, transfer, registration, value
added, alternative or add-on minimum, estimated or other tax of any kind
whatsoever involving Owner, including any interest, penalty or addition thereto,
whether disputed or not.

     "Tax Return" means any return, declaration, report, claim for refund, or
information return or statement relating to Taxes, including any schedule or
attachment thereto, and including any amendment thereof.

     All references in this Agreement to "to the best of Seller's knowledge,"
"Seller's actual knowledge" or words of similar import shall refer only to the
actual (as opposed to deemed, imputed or constructive) knowledge of Richard L.
Perlmutter and John Austin, without inquiry, and notwithstanding any fact or
circumstance to the contrary, shall not be construed to refer to the knowledge
of any other person or entity. Such individuals are named in this Agreement
solely for the purpose of establishing the scope of Seller's knowledge. Such
individuals shall not be deemed to be a party to this Agreement nor to have made
any representations or warranties personally, and no recourse shall be had to
such individuals for any of Seller's representations and warranties hereunder,
and Purchaser hereby waives any liability of or recourse against such
individuals.


                                       18

<PAGE>

     Except as is otherwise expressly provided in this Agreement, Seller hereby
specifically disclaims any warranty (oral or written) concerning: (i) the nature
and condition of the Property and the suitability thereof for any and all
activities and uses that Purchaser elects to conduct thereon; (ii) the manner,
construction, condition and state of repair or lack of repair of the
Improvements; (iii) the compliance of the Land and the Improvements or their
operation with any laws, rules, ordinances or regulations of any government or
other body; and (iv) any other matter whatsoever except as expressly set forth
in this Agreement.

     EXCEPT AS IS OTHERWISE EXPRESSLY PROVIDED IN THIS AGREEMENT, THE SALE OF
THE PROPERTY IS MADE ON A STRICTLY "AS IS" "WHERE IS" BASIS AS OF THE SETTLEMENT
DATE, AND SELLER MAKES NO WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED, OR
ARISING BY OPERATION OF LAW, INCLUDING, BUT IN NO WAY LIMITED TO, ANY WARRANTY
OF QUANTITY, QUALITY, CONDITION, HABITABILITY, MERCHANTABILITY, SUITABILITY OR
FITNESS FOR A PARTICULAR PURPOSE OF THE PROPERTY OR THE PROPERTY, ANY
IMPROVEMENTS LOCATED THEREON OR ANY SOIL CONDITIONS RELATED THERETO.

     PURCHASER SPECIFICALLY ACKNOWLEDGES THAT PURCHASER IS NOT RELYING ON (AND
SELLER HEREBY DISCLAIMS AND RENOUNCES) ANY REPRESENTATIONS OR WARRANTIES MADE BY
OR ON BEHALF OF SELLER OF ANY KIND OR NATURE WHATSOEVER, EXCEPT FOR THOSE
PARTICULAR REPRESENTATIONS AND WARRANTIES EXPRESSLY PROVIDED IN THIS AGREEMENT.
FURTHER, PURCHASER, FOR PURCHASER AND PURCHASER'S SUCCESSORS AND ASSIGNS, HEREBY
RELEASES SELLER FROM, AND WAIVES, ANY AND ALL CLAIMS AND LIABILITIES AGAINST
SELLER FOR, RELATED TO, OR IN CONNECTION WITH, ANY ENVIRONMENTAL OR PHYSICAL
CONDITION AT THE PROPERTY (OR THE PRESENCE OF ANY MATTER OR SUBSTANCE RELATING
TO THE ENVIRONMENTAL CONDITION OF THE PROPERTY), INCLUDING, BUT NOT LIMITED TO,
CLAIMS AND/OR LIABILITIES RELATING TO (IN ANY MANNER WHATSOEVER) ANY HAZARDOUS,
TOXIC OR DANGEROUS MATERIALS OR SUBSTANCES LOCATED IN, AT, ABOUT OR UNDER THE
PROPERTY, OR FOR ANY AND ALL CLAIMS OR CAUSES OF ACTION (ACTUAL OR THREATENED)
BASED UPON, IN CONNECTION WITH, OR ARISING OUT OF, CERCLA, AS AMENDED BY SARA,
AND AS MAY BE FURTHER AMENDED FROM TIME TO TIME, RCRA, OR ANY OTHER CLAIM OR
CAUSE OF ACTION (INCLUDING ANY FEDERAL OR STATE BASED STATUTORY, REGULATORY OR
COMMON LAW CAUSE OF ACTION) RELATED TO ENVIRONMENTAL MATTERS OR LIABILITY WITH
RESPECT TO, OR AFFECTING, THE PROPERTY. PURCHASER REPRESENTS TO SELLER THAT
PURCHASER HAS CONDUCTED, OR WILL CONDUCT PRIOR TO SETTLEMENT, SUCH
INVESTIGATIONS OF THE PROPERTY, INCLUDING BUT NOT LIMITED TO, THE PHYSICAL AND
ENVIRONMENTAL CONDITIONS THEREOF, AS PURCHASER DEEMS NECESSARY TO SATISFY ITSELF
AS TO THE CONDITION OF THE PROPERTY AND THE EXISTENCE OR NONEXISTENCE OF, OR
CURATIVE ACTION TO BE TAKEN WITH RESPECT TO, ANY HAZARDOUS OR TOXIC SUBSTANCES
ON OR DISCHARGED FROM THE LAND OR THE IMPROVEMENTS, AND WILL RELY SOLELY UPON
SAME AND NOT UPON ANY INFORMATION PROVIDED BY, OR ON


                                       19

<PAGE>

BEHALF OF, SELLER, ITS AGENTS AND EMPLOYEES WITH RESPECT THERETO, OTHER THAN
SUCH REPRESENTATIONS AND WARRANTIES OF SELLER AS ARE EXPRESSLY SET FORTH IN THIS
AGREEMENT. UPON SETTLEMENT, PURCHASER SHALL ASSUME THE RISK THAT ADVERSE
MATTERS, INCLUDING BUT NOT LIMITED TO, CONSTRUCTION DEFECTS AND ADVERSE PHYSICAL
AND ENVIRONMENTAL CONDITIONS, MAY NOT HAVE BEEN REVEALED BY PURCHASER'S
INVESTIGATIONS, AND PURCHASER, UPON SETTLEMENT, SHALL BE DEEMED TO HAVE WAIVED,
RELINQUISHED AND RELEASED SELLER FROM AND AGAINST ANY AND ALL CLAIMS, DEMANDS,
CAUSES OF ACTION (INCLUDING CAUSES OF ACTION IN TORT), LOSSES, DAMAGES,
LIABILITIES, COSTS AND EXPENSES (INCLUDING ATTORNEYS' FEES AND COURT COSTS) OF
ANY AND EVERY KIND OR CHARACTER, KNOWN OR UNKNOWN, WHICH PURCHASER MIGHT HAVE
ASSERTED OR ALLEGED AGAINST SELLER, AT ANY TIME BY REASON OF OR ARISING OUT OF
ANY LATENT OR PATENT CONSTRUCTION DEFECTS OR PHYSICAL CONDITIONS, VIOLATIONS OF
ANY APPLICABLE LAWS (INCLUDING, WITHOUT LIMITATION, ANY ENVIRONMENTAL LAWS) AND
ANY AND ALL OTHER ACTS, OMISSIONS, EVENTS, CIRCUMSTANCES OR MATTERS REGARDING
THE PROPERTY.

     PURCHASER ACKNOWLEDGES AND AGREES THAT THE WAIVERS, RELEASES AND OTHER
PROVISIONS CONTAINED IN THIS SECTION 13 WERE A MATERIAL FACTOR IN SELLER'S
ACCEPTANCE OF THE PURCHASE PRICE AND THAT SELLER IS UNWILLING TO SELL THE
PROPERTY (AND THE PROPERTY) TO PURCHASER UNLESS SELLER IS RELEASED AS EXPRESSLY
SET FORTH ABOVE. PURCHASER, WITH PURCHASER'S COUNSEL, HAS FULLY REVIEWED THE
DISCLAIMERS AND WAIVERS SET FORTH IN THIS AGREEMENT, AND UNDERSTANDS THE
SIGNIFICANCE AND EFFECT THEREOF. THE TERMS AND CONDITIONS OF THIS SECTION 13 (C)
WILL EXPRESSLY SURVIVE SETTLEMENT, WILL NOT MERGE WITH THE PROVISIONS OF ANY
SETTLEMENT DOCUMENTS, AND WILL BE INCORPORATED INTO THE DEED.

     Any claim by Purchaser based upon an alleged breach of any representation
or warranty of or by Seller contained herein is intended and shall specifically
be limited by the provisions of Section 11.C. hereof.

     14. Covenants by Seller. Seller covenants and agrees with Purchaser that
from the date hereof until the Settlement Date (as herein defined), Seller shall
cause Owner to conduct its business involving the Property as follows, and
during such period will (except as specifically provided to the contrary
herein):

          A. Refrain from creating on the Property any easements, encumbrances
or liens affecting the Property other than as may be required by any applicable
governmental or quasi-governmental authority or by a provider of utility
services, and refrain from removing any Personal Property, fixture or equipment;
provided, however, nothing herein shall preclude Seller or Owner from replacing
any such items in the ordinary course of operating the Property. Seller shall,
upon Seller's receipt, deliver to Purchaser a copy of any easement so required
by any governmental or quasi-governmental authority or provider of utility
services affecting the


                                       20

<PAGE>

Property which does not require the consent of Purchaser, and any such easement
shall constitute a Permitted Encumbrance.

          B. Refrain from entering into or amending the Contracts (other than
Leases which are governed by Section 14D below) regarding the Property (other
than contracts in the ordinary course of business which are cancelable by Owner
without penalty within thirty (30) days after giving notice thereof) without the
prior written consent of Purchaser, which consent shall not be unreasonably
withheld, delayed or conditioned, and which shall be deemed given if Purchaser
does not object to Seller's request for approval within five (5) business days.

          C. Operate, maintain, repair and insure the Property in a commercially
reasonable manner consistent with the existing operation, maintenance, repair
and insurance of the Property and deliver the Property as of Settlement
substantially in the condition it is in of the date hereof, ordinary wear and
tear, and damage by fire or other casualty excepted (provided that neither
Seller nor Owner shall be obligated to incur costs in excess of $50,000.00 in
connection with such operation, maintenance and/or repair).

          D. Except as expressly provided herein, from and after the date hereof
(provided that this Agreement has not been terminated), Owner shall refrain from
amending the existing Leases without Purchaser's written approval, as provided
below. In addition, from and after the date hereof (provided that this Agreement
has not been terminated), except as expressly provided herein, Seller shall not
permit Owner to enter into any new leases with respect to the Property (each a
"Proposed New Lease"), without Purchaser's written approval, as provided in this
Section 14D. Seller shall furnish Purchaser with a true and correct copy of any
Proposed New Lease into which Owner desires to enter and such financial
information with respect to the proposed tenant as Seller has in its possession.
Purchaser shall have three (3) business days from receipt of such amendment or
Proposed New Lease to approve or disapprove the same, which approval shall not
be unreasonably withheld, conditioned or delayed. In the event that Purchaser
does not approve any such amendment or Proposed New Lease, Purchaser shall
notify Seller, in writing, of such disapproval prior to expiration of the
aforesaid three (3) business day period, stating in such written notification
under what conditions, if any, Purchaser's approval would be forthcoming and
Purchaser's agreement to approve such amendment or Proposed New Lease if such
conditions are satisfied. Notwithstanding the foregoing, Purchaser and Seller
acknowledge and agree that Owner may enter into a new Lease (the "Nextone
Lease") with Nextone Corporation ("Nextone") and a new Lease (the "Harvey Cleary
Lease") with Harvey Cleary, both upon the terms and conditions set forth on
EXHIBIT I. The Nextone Lease shall also provide that Nextone has waived its
right to terminate its 1st floor lease for 11,392 sf and waived its right to
apply the tenant improvement allowance towards rent abatement. All other terms
of the Nextone Lease and the Harvey Cleary Lease shall be subject to Purchaser's
approval as set forth above. Notwithstanding the foregoing, if Seller does not
complete the Lease Transactions, it shall not be a breach of this Paragraph or a
default by Seller or Owner hereunder. The foregoing is not intended and shall
not be construed to prohibit Owner or Seller from entering into any amendment to
a Lease pursuant to a validly exercised renewal or expansion right on the part
of any Tenant as is specifically set forth in its Lease.

          E. Promptly provide Purchaser with copies of all written notices
delivered or received under the Leases.


                                       21

<PAGE>

          F. Promptly provide Purchaser a copy of any notice of litigation
received by Seller that may materially and adversely affect the ownership or
operation of the Property.

     15. Purchaser's Closing Conditions Precedent. Purchaser's obligation to
consummate the transaction contemplated by this Agreement shall be subject to
satisfaction or waiver of each of the following conditions ("Purchaser's Closing
Conditions Precedent"); provided, however that Purchaser shall have the
unilateral right to waive any Purchaser's Closing Conditions Precedent, in whole
or in part, by written notice to Seller:

          A. The representations of Seller herein shall be, in all material
respects, true and complete as of Settlement.

          B. Seller shall have performed all of the obligations required to be
performed by Seller under this Agreement, as and when required by this
Agreement, in all material respects.

          C. There shall not have been instituted and be pending any action or
proceeding before any court, governmental agency or other regulatory or
administrative agency or commission challenging the purchase and sale of the
Argo Membership Interests or the FLLP Membership Interests or the transactions
related thereto that seeks to restrain, prevent or change the transactions
contemplated hereby or questions the validity of such transactions.

          D. Neither the Purchaser nor the Seller shall have terminated this
Agreement as provided herein.

          E. Purchaser shall have received an estoppel certificate,
substantially in the form attached to the Leases or, if no such form is
attached, in the form of EXHIBIT J attached hereto and made a part hereof, with
such additional information or modifications reasonably approved by Purchaser,
from (i) Tenants under Leases (the "Estoppel Certificates"). Seller and
Purchaser agree that Seller shall not be in default under this Agreement if
Seller is unable to obtain an Estoppel Certificate from one or more of the
Tenants and that no costs, expenses or other damages shall be due to Purchaser
in such event. Seller shall, and shall cause Owner to, use reasonable efforts to
obtain such Estoppel Certificates from each Tenant; provided, however, neither
Seller nor Owner shall be required to expend significant monies or make
significant concessions or institute litigation in order to obtain such Estoppel
Certificates. If Seller has received Estoppel Certificates from Tenants under
Leases constituting at least eighty five percent (85%) of the rentable square
feet of the occupied portion of the Property (which shall include an estoppel
from Nextone irrespective of whether it is then in occupancy), Seller shall be
deemed to have satisfied the condition set forth in this subsection 15E.

          F. The Lease Transactions shall have been consummated.

     16. Business Days. Any date specified in this Agreement which falls on a
Saturday, Sunday or legal holiday in the State of Maryland shall be extended to
the first regular business day after such date which is not a Saturday, Sunday
or legal holiday.

     17. Confidentiality. Between the date of this Agreement and Settlement, the
Purchaser (i) will hold and will use reasonable efforts to cause its officers,
directors, employees, accountants, representatives, agents, consultants, and
advisors (collectively, its


                                       22

<PAGE>

"Representatives") to hold in strict confidence, all information furnished to
the Purchaser or its Representatives by the Seller or its representatives in
connection with the transactions contemplated by this Agreement as well as all
information concerning the Property contained in any analyses, compilations,
studies, or other documents prepared by or on behalf of the Purchaser
(collectively, the "Information"); and (ii) will not, without the prior written
consent of Seller, release or disclose any of the Information to any other
person, except (1) to the Purchaser's Representatives (a) who need to know the
Information in connection with the consummation of the transactions contemplated
by this Agreement, (b) who are informed by the Purchaser of the confidential
nature of the Information, and (c) who agree to be bound by the terms and
conditions of this Section 17 and (2) to the extent required by law (including
disclosure by the Purchaser, as determined in Purchaser's sole discretion, in
any registration statement or other filing with the U.S. Securities and Exchange
Commission). Information shall not include any information which can be shown to
be or have become (A) generally available to the public other than as a result
of a disclosure by the Purchaser or its Representatives or (B) available to the
Purchaser on a non-confidential basis from a source other than Seller or its
agents, provided that such source is entitled to disclose such information.
Except as permitted in this Section 17, neither Purchaser or Seller shall
disclose the terms of this Agreement to any third party. The terms of this
Section 17 shall survive settlement.

     In the event the Purchaser or any person to whom the Purchaser transmits
the Information pursuant to this Agreement becomes legally compelled to disclose
any of the Information prior to Settlement, Purchaser (a) will provide Seller
with prompt notice thereof so that Seller may seek a protective order or another
appropriate remedy and/or waive compliance with the provisions of this Section
17, (b) will furnish only that portion of the Information which the Purchaser is
(as advised by counsel) legally required to disclose, and (c) will cooperate
with Seller in obtaining, at Seller's expense, a protective order or another
reliable assurance that confidential treatment will be accorded to the
Information. If the transactions contemplated by this Agreement are not
consummated, any documents or other materials containing Information will be
returned to the Seller immediately upon the Seller's request therefore.

     18. Montgomery County Disclosures. The following disclosures are made
pursuant to applicable law in Montgomery County, Maryland:

          A. GENERAL/MASTER PLANS. Purchaser acknowledges that Purchaser has
been apprised of Purchaser's rights to review the applicable master plan and the
municipal land use plan and any related amendments, including maps showing
planned land uses, roads and highways, and the location and nature of proposed
parks and other public facilities affecting the Property prior to the execution
of this Agreement. Purchaser acknowledges that Purchaser is aware that the
applicable plan or general plan for Montgomery County is available at the
Maryland National Capital Park and Planning Commission and that at no time did
Seller explain to Purchaser the intent or meaning of such a plan nor did
Purchaser rely on any representations made by Seller pertaining to the
applicable master plan or general plan

          B. NOTICE AND DISCLOSURE OF AVAILABILITY OF SEWAGE DISPOSAL SYSTEM IN
DESIGNATED AREAS.


                                       23

<PAGE>

               (i) Notice is hereby given to Purchaser, pursuant to the
Montgomery County Code, of the obligation of Seller, or Seller's duly authorized
agent, to disclose to Purchaser any information known to Seller as to whether
the Property is connected to, or has been authorized for connection to, a
community sewerage system, and if not, whether an individual sewage disposal
system has been constructed on the Property, or whether the Property has been
disapproved by the county for the installation of any individual sewage disposal
system.

               (ii) If an individual sewage disposal system has been or is to be
installed upon the Property, and if the Property is located in a subdivision,
and if Purchaser received a copy of the subdivision record plat, as provided
above, Purchaser indicates that Purchaser has reviewed the said record plat,
including any provisions thereon with regard to areas restricted for the initial
and reserve well locations and the individual sewer disposal systems, and the
restricted area in which construction of the building to be served by the
individual sewage disposal system is permitted.

          C. MASTER PLAN AND MUNICIPAL LAND USE PLAN. By signing this Agreement,
Purchaser hereby acknowledges: (1) Seller has offered Purchaser the opportunity
to review the applicable master plan and municipal land use plan and any adopted
amendment; (2) Seller has informed Purchaser that amendments affecting the plan
may be pending before the planning board or the county council or a municipal
planning body; (3) (a) Purchaser has reviewed each plan and adopted amendment,
or (b) Purchaser has waived the right to review each plan and adopted amendment;
and (4) Purchaser understands that, to stay informed of future changes in county
and municipal land use plans, the Purchaser should consult the planning board
and the appropriate municipal planning body.

     19. Miscellaneous.

          A. NOTICES. Any and all notices, requests, consents, approvals or
other communications hereunder shall be deemed to have been duly given only if
in writing and if transmitted by hand delivery with receipt therefor, by
recognized overnight courier, or by registered or certified mail, return receipt
requested, first-class postage prepaid addressed as follows (or to such new
address as the addressee of such a communication may have notified the sender
thereof):

               To Seller:       c/o Argo Investment Company, LC
                                9600 Rockwell Road
                                Suite 200
                                Rockville, Maryland 20850
                                Attn: Mr. Richard L. Perlmutter
                                Facsimile: (240) 499-9686

               With copy to:    J. Richard Saas, Esq.
                                Tenenbaum & Saas, P.C.
                                4504 Walsh Street
                                Suite 200
                                Chevy Chase, Maryland 20815
                                Facsimile: (301) 961-5305


                                       24

<PAGE>

               To Purchaser:    Columbia Equity Trust, Inc.
                                1750 H Street, NW
                                Suite 500
                                Washington, DC 20006
                                Attn: Mr. Oliver T. Carr, III
                                Facsimile: (202) 303-3088

               With copy to:    John M. Ratino, Esq.
                                Hunton & Williams LLP
                                1900 K Street, NW
                                Washington, DC 20006
                                Facsimile: (202) 778-2201

               To Escrow Agent: LandAmerica Commercial Services
                                1015 15th Street, NW
                                Suite 300
                                Washington, DC 20005
                                Attn: Sarah (Sally) Eckert Webb
                                Facsimile: (202) 737-4108

          B. GOVERNING LAW. This Agreement shall be construed and enforced in
accordance with the laws of the State of Maryland, without regard to choice of
law principles.

          C. HEADINGS. The captions and headings herein are for convenience and
reference only and in no way define or limit the scope or content of this
Agreement or in any way affect its provisions.

          D. EFFECTIVE DATE. This Agreement shall be effective as of the date of
full and final execution and delivery hereof by Purchaser and Seller. The term
"Effective Date" means the latest of the dates set forth after the signatures on
behalf of Seller and Purchaser on the signature page of this Agreement.

          E. COUNTERPART COPIES. This Agreement may be executed in two or more
counterpart copies, all of which counterparts shall have the same force and
effect as if all parties hereto had executed a single copy of this Agreement.

          F. BINDING EFFECT; ASSIGNMENT. This Agreement shall be binding upon,
and inure to the benefit of, the parties hereto and their respective successors
and assigns; provided, however, that Purchaser shall not be entitled to assign
this Agreement without the prior written consent of Seller, which consent shall
be given or withheld at Seller's sole discretion; provided, however, that
Purchaser shall be entitled to assign its rights under this Agreement without
Seller's consent (but with not less than 10 days prior written notice to Seller,
which notice shall include a copy of the proposed written assignment) at and as
of the Settlement Date (but not prior thereto) to an entity in which Purchaser
or Columbia Equity, LP, directly or indirectly, is the equity owner (a
"Purchaser Affiliate"), provided that such assignment shall not release
Purchaser of or from its obligations hereunder. Purchaser shall have the right
to designate any


                                       25

<PAGE>

Purchaser Affiliate as the party to receive and assume the Argo Membership
Interests and the FLLP Membership Interests at Settlement.

          G. ENTIRE AGREEMENT. This Agreement and the Exhibits attached hereto
contain the final and entire agreement between the parties hereto with respect
to the sale and purchase of the Property and are intended to be an integration
of all prior negotiations and understandings. Purchaser and its agents, and
Seller and its agents, shall not be bound by any terms, conditions, statements,
warranties or representations, oral or written, not contained herein. No change
or modifications to this Agreement shall be valid unless the same is in writing
and signed by the parties hereto. No waiver of any of the provisions of this
Agreement shall be valid unless the same is in writing and is signed by the
party against with which it is sought to be enforced.

          H. RATIFICATION. Each party shall have three (3) days from the date of
execution by the other to ratify this Agreement and deliver a copy of same to
the other after which time without ratification the offer encompassed herein
shall be null and void.

          I. RISK OF LOSS. The risk of loss to the Property shall remain with
Seller and shall pass to Purchaser simultaneously with delivery of a deed to the
Property to Purchaser.

          J. SURVIVAL. The terms and provisions of this Agreement shall survive
Settlement and delivery of a deed, and shall not be merged therein.

          K. EXHIBITS.

               A    Land

               B    Personal Property

               C    List of Contracts

               D    List of Leases

               E    Information

               F    Rent Roll

               G    Insurance

               H    Banking Relationships

               I    Nextone Lease Terms

               J    Form of Estoppel Certificate

               K    Limited Partnership Agreement of Foulger

               L.   Tenancy in Common Agreement

               M.   Operating Agreement of Argo

               N.   Lender's Escrow Accounts

          L. RECORDATION. Neither this Agreement nor any memorandum or other
summary of this Agreement shall be placed of public record except with the prior
written consent of the Seller and the Purchaser.

          M. TAX DEFERRED EXCHANGE. The Seller shall have the right to structure
the transaction specified herein as a like-kind exchange under Section 1031 of
the Internal Revenue Code ("Section 1031") by providing written notice to
Purchaser at least five (5) days prior to


                                       26

<PAGE>

Settlement, provided that such structuring of the transaction shall not delay
Settlement. In the event the Seller elects to exercise its rights under this
section, then Settlement shall occur in accordance with the terms hereof except
that Seller and an accommodation party (the "Accommodator") permitted by the
regulations promulgated under Section 1031 shall, at Settlement, execute a
mutually acceptable escrow agreement dealing with the retention of the Purchase
Price by the Accommodator and the acquisition of exchange property by the
Accommodator that Seller will receive pursuant to the escrow.

     In the event that Seller elects to exercise its rights to structure this
transaction as a like-kind exchange under Section 1031, the Purchaser agrees to
cooperate with Seller so long as (i) there is no additional financial or other
liability or expense imposed upon the Purchaser, (ii) the rights of Purchaser
are not affected thereby, and (iii) Purchaser has no obligation to acquire land
or property used in such like-kind exchange.

          N. EXCULPATION. Purchaser agrees to look solely to the Seller's
interest in the Owner and the Owner's interest in the Property and, subject to
the limitation set forth in Section 11 hereof, a portion of the proceeds
therefrom, in connection with any recourse against any Seller arising pursuant
to this Agreement. Seller agrees to maintain the legal existence of FLLP, and
the Argo Sellers with an aggregate net worth of at least Two Million Dollars
($2,000,000) for at least one (1) year after Settlement. Purchaser agrees that
no adviser, member, shareholder, trustee, director, officer, partner, employee,
affiliate or subsidiary of any Seller, and no adviser, partner, shareholder,
trustee, director, officer, employee, affiliate or subsidiary of any of the
foregoing shall have any liability under or with respect to this Agreement
solely as a result of such relationship.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement or have
caused this Agreement to be executed on their behalf, under seal, on the date or
dates set forth below.

WITNESS:                                SELLER:

                                        Foulger Land Limited Partnership,
                                        a Virginia limited partnership

                                        By: Sid Foulger (Orchard Ridge), Inc.,
                                            a Maryland corporation,
                                            its General Partner


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


                                        Argo Orchard Ridge, LC,
                                        a Maryland limited liability company


                                       27

<PAGE>

                                        By: Argo Orchard Ridge Manager, Inc.,
                                            a Maryland corporation,
                                            its Managing Member


                                        By: /s/ John Austin
-------------------------------------       ------------------------------------
                                        Name: John Austin
                                        Title: Member


                                        PURCHASER:

                                        Columbia Equity Trust, Inc.,
                                        a Maryland corporation


/s/ John Schissel                       By: /s/ Oliver T. Carr, III
-------------------------------------       ------------------------------------
                                        Name: Oliver T. Carr, III
                                        Title: CEO


                                       28

<PAGE>

                                    EXHIBIT E

                                101 ORCHARD RIDGE

              REQUESTED PROPERTY DATA (TO THE EXTENT IN SELLERS' OR
                         OWNERS' POSSESSION OR CONTROL)

     1. Basic property description with detail on systems, structure and site;
RECEIVED

     2. Reduced (8-1/2 x 11) floor plans and current site plan;

     3. Most recent ALTA survey; RECEIVED

     4. Quince Orchard Park covenants, easements and restrictions and owner's
association agreements;

     5. All executed leases and subleases (with amendments thereto) regarding
all space occupied by tenants at the Property; RECEIVED

     6. Copies of the tax and utility bills for the Property for calendar years
2004, 2005, and 2006 YTD; RECEIVED

     7. Operating statements (including operating expense information) prepared
by the property manager for the calendar years 2004, 2005 and 2006 YTD; RECEIVED

     8. Capital expenditure program details for 2003, 2004, 2005 and 2006,
including any vendor studies/bids (systems, fire/life safety, structure, ADA);
RECEIVED (GL ONLY; NO DETAIL)

     9. The most recent environmental site assessment report and any soils
reports; RECEIVED PREVIOUS PHASE I

     10. Construction and Design Documents: Base Building Documents (as-built
plans and specifications) plus any revisions, Tenant Improvement Plans, Public
Space Finish Specifications (if different from Base Building Plans), Close out
Manual for each TI project, CADD drawings on disk, documentation and plans for
any subsequent renovations to the base building;

     11. Property Management: Control system plans as built and instructions;

     12. Mechanical operation and maintenance logs in Sellers possession;

     13. Copies of all warranties and warranty information; ROOF WARRANTY
RECEIVED

     14. Certificate of occupancy/non-Residential Use Permits for the Property
and all Tenant space therein; RECEIVED

     15. Seller's operating budget for the Property for 2006; RECEIVED

     16. A current rent roll for the Property in the form currently maintained
by Seller; RECEIVED

     17. List of all security deposits/letters of credit/tenant financial
statements provided to Seller or Lender; RECEIVED CALCULATION OF SECURITY
DEPOSITS HELD

<PAGE>

     18. List of all rent abatements, outstanding leasing commissions and
Landlord payments to the Tenants (including but not limited to tenant
improvement allowances and architectural fees for test fits);

     19. UBS loan documents; RECEIVED

     20. Evidence of insurance delivered by the Tenants as required under the
Leases; RECEIVED

     21. A list of all mechanical equipment and service agreements including
service, maintenance, equipment and/or supply contracts, and amendments thereto;

     22. Copies of any audits of reimbursable expenses reconciliations for 2004,
2005 and 2006 (if prepared); 2006 WILL NOT BE COMPLETED UNTIL APRIL

     23. Month-by-month Account Receivables delinquency/aging report for
trailing 12 months; RECEIVED and

     24. Seller's architect's schedule and plans to support the rentable square
footage and gross building area calculations using the current BOMA method of
measurement, to the extent the same is in Seller's possession.


                                      E-30

<PAGE>

                                    EXHIBIT I

                                101 ORCHARD RIDGE

Nextone Lease - Suite 300: Size - 26,743 SF; Maturity Date - 10 years from
execution; Base Rent - $29.83/SF (as of 6/1/06); Escalation - 3% per annum w/
June 1 escalation date.

Harvey Cleary - Suite 350: Size - 8,012 SF; Maturity Date - July 2008; Base Rent
- $26.74/SF (as of 6/1/06); Escalation - 3% per annum w/ Aug. 1 escalation date.


                                      E-31