FIRST AMENDMENT TO AMENDED AND RESTATED TAX INDEMNITY AGREEMENT

EXHIBIT 10.6

FIRST AMENDMENT TO AMENDED AND RESTATED TAX INDEMNITY AGREEMENT

THIS FIRST AMENDMENT TO AMENDED AND RESTATED TAX INDEMNITY AGREEMENT (the "Agreement") is made and entered into this 21st day of November, 2006 by and among PRIME GROUP REALTY, L.P. , a Delaware limited partnership ("Prime"), RICHARD   A. HEISE ("Heise"), CTA GENERAL PARTNER, LLC , a Delaware limited liability company ("General Partner"), and CONTINENTAL TOWERS, L.L.C. , a Delaware limited liability company ("Newco").

WHEREAS , Prime, Heise, General Partner and Newco entered into that certain Amended and Restated Tax Indemnity Agreement dated as of January 10, 2006 ("TIA");

WHEREAS , Heise and General Partner are the only partners in Continental Towers Associates-I, L.P., an Illinois limited partnership ("CTA") and General Partner is the sole general partner of CTA;

WHEREAS , CTA is the only member of Continental Towers Associates II, LLC, a Delaware limited liability company ("CTAII");

WHEREAS , CTAII is the sole member of Continental Towers Associates III, LLC, a Delaware limited liability company ("CTAIII");

WHEREAS, concurrently with the execution and delivery of this First Amendment, (a) CTA, the owner of an undivided 36% interest in the Real Estate (as defined in the TIA), will transfer all of its right, title and interest in and to the Real Estate to CTAIII; (b) Heise and General Partner will enter into a Dissolution pursuant to which (i) Heise will redeem his 96.7429% partnership interests in CTA in exchange for a 96.7429% membership interest in CTAII, and (ii) General Partner will redeem its 3.2571% partnership interest in CTA in exchange for a 3.2571% interest in CTAII; and (iii) CTA will be dissolved; (c) CTAIII, as successor in interest to CTA, and Newco, the owner of an undivided 64% interest in the Real Estate, will enter into a First Amendment of the Co-Ownership Agreement (as defined in the TIA); (d) CTAIII and Newco will refinance the Senior Loan with CWCapital LLC; and

WHEREAS , the parties desire to amend the TIA to reflect the new ownership structure for the Real Estate, the new Senior Loan, and to make certain other changed to which the parties have agreed;

NOW, THEREFORE , in consideration of the matters set forth in the recitals and the mutual covenants set forth hereafter, the parties agree as follows:

1.              The definitions of " Senior Lender ", " Senior Loan ", " Senior Loan Documents " and " Senior Loan Agreement " in Section 1 of the TIA are hereby deleted in their entirety and the following inserted in lieu thereof:

" Senior Lender " shall have the meaning set forth in Section 2c .

" Senior Loan " shall have the meaning set forth in Section 2c .

" Senior Loan Agreement " shall have the meaning set forth in Section 2c .

" Senior Loan Documents " shall have the meaning set forth in Section 2c .

2.              The definition of "Indemnification Event" in Section 1 of the TIA is hereby amended by inserting ", CTAII, CTAIII" after each reference to "CTA" in said definition.

3.              The definition of "Tax Event" in Section 1 of the TIA is hereby amended by deleting the reference to "CTA" and inserting "CTAII" in lieu thereof.

4.              The following subsection c is hereby inserted into Section 2 of the TIA as if fully set forth therein:

"c.             New 2006 Transaction . Prime, Heise, and certain Affiliates of the foregoing are entering into the following agreements (items (i), (ii), (iii) and (iv) below are collectively referred to as the " New 2006 Transaction "):

(ii)            Heise and General Partner will cause CTA to transfer and assign by Special Warranty Deed all of its right, title and interest in and to the Real Estate (being an undivided 36% interest as a tenant in common with Newco) to CTAIII, subject to the Junior Loan and the Senior Loan.

(iii)           Heise and General Partner will enter into that certain Dissolution Agreement dated as of the date hereof pursuant to which CTA will be dissolved and will distribute a 96.7429% membership interest in CTAIII to Heise and a 3.2571% membership interest in CTAII to CTA General Partner.

(iv)           Heise and General Partner will enter into that