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                                                                    Exhibit 10.2

                                                               CHICAGO, ILLINOIS

$160,000,000.00   DATED: AS OF DECEMBER 13, 1999

                  FOR VALUE RECEIVED, 330 N. WABASH AVENUE, L.L.C., a Delaware
limited liability company, having its principal place of business at c/o Prime
Group Realty Trust, 77 West Wacker Drive, Suite 3900, Chicago, Illinois 60601
("BORROWER"), promises to pay to the order of WESTDEUTSCHE IMMOBILIENBANK, a
banking institution organized under the laws of the Federal Republic of Germany,
at its principal place of business at Wilhelm Theodor Romheld Strasse 24, 55130
Mainz, Federal Republic of Germany, or at such place as the holder hereof may
from time to time designate in writing, individually and as agent (including any
successors and assigns, "AGENT") for Merrill Lynch Mortgage Capital Inc., a
Delaware corporation, having an address at World Financial Center, North Tower,
10th Floor, 250 Vesey Street, New York, New York 10281, and such other
co-lenders as may exist from time to time (collectively with Agent, "LENDERS"
and each individually "LENDER"), the principal sum of ONE HUNDRED SIXTY MILLION
DOLLARS (US$160,000,000.00), in lawful money of the United States of America,
with interest thereon to be computed from the date funds are advanced by Agent
on the outstanding principal balance of the Loan from time to time at the
applicable interest rate (as set forth in the Loan Agreement), and the principal
balance of which is to be paid in installments as set forth on SCHEDULE A
attached hereto and made a part hereof, or as more fully set forth in the Loan
Agreement. Capitalized terms not defined herein but defined in the Loan
Agreement shall have the meanings ascribed thereto in the Loan Agreement.

Section 1.              DEFINITIONS. As used in this Note, the following terms
shall have the following definitions:


                  "LOAN AGREEMENT" means that certain Loan Agreement dated as of
         the date hereof by and among Agent, Borrower and Lenders (as the same
         may be amended, modified or supplemented from time to time in
         accordance with terms thereof).

                  "LOAN DOCUMENTS" relates collectively to the Note, the
         Mortgage, the Loan Agreement, the Environmental Indemnity Agreement,
         the Cash Collateral Agreement, the Other Security Documents and any and
         all other documents executed in connection with this Note.

                  "OTHER SECURITY DOCUMENTS" as used in this Note shall mean all
         and any of the documents other than this Note, the Mortgage, or the
         Environmental Indemnity Agreement now or hereafter executed by Borrower
         and/or others and by or in favor of Agent and/or Lenders, which wholly
         or partially secure or guarantee payment of this Note.

Section 1.             PAYMENT AND CALCULATION OF INTEREST. Interest on the
outstanding principal indebtedness evidenced hereby shall be paid and calculated
as set forth in the Loan Agreement, and the provisions of Section 2.3 of the
Loan Agreement are hereby incorporated in this Note by reference as if set forth
herein at length.


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Section 1.             APPLICATION OF PAYMENT. Payments under this Note shall
be applied first to the payment of accrued interest and other costs and charges
then due and payable in connection with this Note or the Debt (as defined in the
Mortgage), as Agent may determine in its sole discretion, and the balance shall
be applied toward the reduction of the principal balance of the Loan. All
amounts due under this Note shall be payable without setoff, counterclaim or any
other deduction whatsoever.

Section 1.             SECURITY. This Note is secured by the Mortgage, the Cash
Collateral Account, the Environmental Indemnity Agreement, the Other Security
Documents and such other cash collateral accounts contemplated by the Loan
Documents as may be pledged to Agent and/or Lenders from time to time.

Section 1.             EVENT OF DEFAULT. The provisions of Article 5 of the
Loan Agreement are hereby incorporated in this Note by reference as if set forth
herein at length. In addition to the foregoing, in the event that it should
become necessary to employ counsel to collect the Debt or to protect or
foreclose the security hereof, Borrower also agrees to pay on demand all actual,
out-of-pocket costs of collection incurred by Agent, including reasonable
attorneys' fees and disbursements for the services of counsel whether or not
suit be brought.

Section 1.              DEFAULT RATE. The provisions of Section 2.6 of the Loan
Agreement are hereby incorporated in this Note by reference as if set forth
herein at length. In addition to the foregoing, accrual of interest at the
Default Rate shall be computed from the occurrence of the Event of Default until
all such Events of Default have been fully cured. Any interest computed at the
Default Rate shall be added to the Debt (as defined in the Mortgage), and shall
be deemed secured by the Mortgage. This clause, however, shall not be construed
as an agreement or privilege to extend the date of the payment of the Debt, nor
as a waiver of any other right or remedy accruing to Lenders by reason of the
occurrence of any Event of Default.

Section 1.              PREPAYMENT. The provisions of Sections 2.8 and 2.9 of
the Loan Agreement are hereby incorporated in this Note by reference as if set
forth herein at length.

Section 1.              PAYMENT AFTER DEFAULT. If following the occurrence and
during the continuance of any Event of Default, Borrower shall tender payment of
an amount sufficient to satisfy the Debt at any time prior to a sale or
realization of the Collateral, either through foreclosure or the exercise of the
other remedies available to Agent under the Mortgage or the Loan Agreement, such
tender by Borrower shall be deemed to be a voluntary prepayment under this Note
in the amount tendered. At the time of such tender, Borrower shall, in addition
to the entire Debt, also pay to Agent the applicable prepayment consideration
specified in Section 2.9 and/or 2.8 of the Loan Agreement.

Section 2.             USURY. This Note is subject to the express condition
that at no time shall Borrower be obligated or required to pay interest on the
Debt at a rate which could subject Lenders to either civil or criminal liability
as a result of being in excess of the maximum interest rate which Borrower is
permitted by applicable law to contract or agree to pay. If by the terms of


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this Note, Borrower is at any time required or obligated to pay interest on the
Debt at a rate in excess of such maximum rate, the rate of interest due under
this Note shall be deemed to be immediately reduced to such maximum rate and all
previous payments in excess of the maximum rate shall be, at the discretion of
Agent, refunded to Borrower or deemed to have been payments in reduction of
principal balance of the Loan and not on account of the interest due hereunder.
In the event of reduction of the principal balance of the Loan pursuant to this
Section 9 no prepayment penalty, premium or other charges, including, without
limitation, the Early Prepayment Premium or the Prepayment Premium, shall be
payable to Lenders or Agent.

Section 1.             MODIFICATION, WAIVER, CONSENT. This Note may not be
modified, amended, waived, extended, changed, discharged or terminated orally or
by any act or failure to act on the part of Borrower or Agent, but only by an
agreement in writing signed by the party against whom enforcement of any
modification, amendment, waiver, extension, change, discharge or termination is
sought. Whenever used, the singular number shall include the plural, the plural
the singular, and the words "Agent" and "Borrower" shall include their
respective successors, assigns, heirs, executors and administrators.

Section 1.              WAIVER. Borrower and all others who may become liable
for the payment of all or any part of the Debt do hereby severally waive all
notices excluding those required to be given under the Loan Documents. No
release of any security for the Debt or any person liable for payment of the
Debt, no extension of time for payment of this Note or any installment hereof,
and no alteration, amendment or waiver of any provision of the Loan Documents
made by agreement between Agent and any other person or party shall release,
modify, amend, waive, extend, change, discharge, terminate or affect the
liability of Borrower, and any other person or party who may become liable for
the payment of all or any part of the Debt, under the Loan Documents.

Section 1.             LIMITED RECOURSE. The provisions of Section 6.1 of the
Loan Agreement are hereby incorporated in this Note by reference as if set forth
herein at length.

Section 1.             AUTHORITY OF BORROWER. Borrower (and the undersigned
representative of Borrower, if any) represents that Borrower has full power,
authority and legal right to execute, deliver and perform its obligations
pursuant to this Note, the Mortgage and the other Loan Documents and that this
Note, the Mortgage and the other Loan Documents constitute valid and binding
obligations of Borrower.

Section 1.             NOTICE. All notices or other communications required or
permitted to be given pursuant hereto shall be given in the manner specified in
the Mortgage directed to the parties at their respective addresses as provided
therein.

Section 1.             TRANSFER OF MORTGAGED PROPERTY. Without the prior
written consent of Agent, Borrower shall not sell, convey, alienate, mortgage,
encumber, pledge or otherwise transfer, or permit the transfer of, directly or
indirectly, the Mortgaged Property or ownership interests of Borrower, except as
permitted in the Loan Documents.


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Section 1. [Intentionally Omitted]

Section 1.             SUCCESSORS AND ASSIGNS. This Note shall be binding upon
and shall inure to the benefit of Lenders and Borrower and their respective
successors and assigns permitted hereunder or under the other Loan Documents.

Section 1.             JURY TRIAL. BORROWER HEREBY, TO THE FULLEST EXTENT THAT
IT MAY LAWFULLY DO SO, WAIVES TRIAL BY JURY IN ANY ACTION OR PROCEEDING WITH
RESPECT TO THIS NOTE. THIS WAIVER OF RIGHT TO TRIAL BY JURY IS GIVEN KNOWINGLY
AND VOLUNTARILY BY BORROWER, AND IS INTENDED TO ENCOMPASS INDIVIDUALLY EACH
INSTANCE AND EACH ISSUE AS TO WHICH THE RIGHT TO TRIAL BY JURY WOULD OTHERWISE
ACCRUE. AGENT IS HEREBY AUTHORIZED TO FILE A COPY OF THIS PARAGRAPH IN ANY
PROCEEDING AS CONCLUSIVE EVIDENCE OF THIS WAIVER BY BORROWER.

Section 1.             GOVERNING LAW. This Note shall be governed by and
construed in accordance with the laws of the State of New York and the
applicable laws of the United States of America.

                  IN WITNESS WHEREOF, Borrower and Agent have duly executed this
Agreement the day and year first above written.

                           BORROWER:

                           330 N. WABASH AVENUE, L.L.C.

                           By: 77 West Wacker Limited Partnership, its


                           By:   Prime Group Realty L.P., its general partner

                                 By:  Prime Group Realty Trust, its managing
                                      general partner

                                      By:    /s/ Jeffrey A. Patterson
                                             ------------------------
                                             Jeffrey A. Patterson
                                             Executive Vice President


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                                   SCHEDULE A

                         PRINCIPAL AMORTIZATION SCHEDULE
<TABLE>
<S>                                         <C>                        <C>
                                            December 13, 2000          $1,600,000
                                            December 13, 2001          $3,200,000
                                            December 13, 2002          $3,200,000

In respect of the First Extension

Period, if applicable                       December 13, 2003          $4,800,000

In respect of the Second Extension

Period, if applicable                       December 13, 2004          $4,800,000
</TABLE>