AMENDED AND RESTATED ENVIRONMENTAL AND HAZARDOUS SUBSTANCE INDEMNIFICATION AGREEMENT

EXHIBIT 10.68

AMENDED AND RESTATED

ENVIRONMENTAL AND HAZARDOUS SUBSTANCE

INDEMNIFICATION AGREEMENT

THIS AMENDED AND RESTATED ENVIRONMENTAL AND HAZARDOUS SUBSTANCE INDEMNIFICATION AGREEMENT (this “ Agreement ”), made as of December 29, 2006, is by CONTINENTAL TOWERS ASSOCIATES III, LLC , a Delaware limited liability company, (the “ Borrower ”), whose address is c/o Prime Group Realty Trust, 77 West Wacker Drive, Suite 3900, Chicago, Illinois 60601, in favor of WELLS FARGO BANK, N.A., as trustee for the registered holders of COBALT CMBS COMMERCIAL MORTGAGE TRUST 2006-C1, COMMERCIAL MORTGAGE PASS-THROUGH CERTIFICATES, SERIES 2006-C1 (together with its successors and assigns, “ Lender ”), having an address at c/o CWCapital LLC, One Charles River Place, 63 Kendrick Street, Needham, Massachusetts 02494.

W I T N E S S E T H:

WHEREAS, Lender has extended to Borrower a loan in the principal amount of FORTY-ONE MILLION FOUR HUNDRED THOUSAND AND NO/100 DOLLARS ($41,400,000.00 ) (the “ Loan ”); and

WHEREAS, the Loan is evidenced by an Amended and Restated Promissory Note dated of even date herewith (the “ Note ”), executed by Borrower and payable to the order of Lender in the principal amount of the Loan and is secured by an Amended and Restated Mortgage, Security Agreement and Fixture Financing Statement dated of even date herewith (the “ Security Instrument ”), made by Borrower in favor of Lender, encumbering the real property, buildings, structures and other improvements described therein (collectively, the “ Property ”) and by other documents and instruments (the Note, the Security Instrument and such other documents and instruments, as the same may from time to time be amended, consolidated, renewed or replaced, being collectively referred to herein as the “ Loan Documents ”); and

WHEREAS, as a condition to making the Loan, Lender has required that Borrower indemnifies Lender with respect to hazardous wastes on, in, under or affecting the Property as herein set forth.

NOW, THEREFORE, to induce Lender to extend the Loan to Borrower and in consideration of the foregoing premises and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Borrower hereby covenants and agrees for the benefit of Lender, as follows:

1.              Indemnity . Borrower hereby assumes liability for, and hereby agrees to pay, protect, defend (at trial and appellate levels) and with attorneys, consultants and experts

AMENDED AND RESTATED ENVIRONMENTAL AND HAZARDOUS SUBSTANCE

INDEMNIFICATION AGREEMENT - Page 1

43412-20/Continental Towers

acceptable to Lender, and save Lender harmless from and against, and hereby indemnifies Lender from and against any and all liens, damages, losses, liabilities, obligations, settlement payments, penalties, assessments, citations, directives, claims, litigation, demands, defenses, judgments, suits, proceedings, costs, disbursements and expenses of any kind or of any nature whatsoever (including, without limitation, reasonable attorneys’, consultants’ and experts’ fees and disbursements actually incurred in investigating, defending, settling or prosecuting any claim, litigation or proceeding) (collectively “ Costs ”) which may at any time be imposed upon, incurred by or asserted or awarded against Lender or the Property, and arising directly or indirectly from or out of: (i) the violation of any local, state or federal law, rule or regulation pertaining to environmental regulation, contamination or clean-up (collectively, “ Environmental Laws ”), including, without limitation, the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (42 U.S.C. §9601 et seq. and 40 CFR §302.1 et seq.), the Resource Conservation and Recovery Act of 1976 (42 U.S.C. §6901 et seq.), The Federal Water Pollution Control Act (33 U.S.C. §1251 et seq. and 40 CFR §116.1 et seq.), and the Hazardous Materials Transportation Act (49 U.S.C. §1801 et seq.), and the regulations promulgated pursuant to said laws, all as amended, relating to or affecting the Property, whether or not caused by or within the control of Borrower; (ii) the presence, release or threat of release of any hazardous, toxic or harmful substances, wastes, materials, pollutants or contaminants (including, without limitation, asbestos, polychlorinated biphenyls, petroleum products, flammable explosives, radioactive materials, infectious substances or raw materials which include hazardous constituents) or any other substances or materials which are included under or regulated by Environmental Laws (collectively, “ Hazardous Substances ”), on, in, under or effecting all or any portion of the Property or any surrounding areas, regardless of whether or not caused by or within the control of Borrower; (iii) the failure by Borrower to comply fully with the terms and conditions of this Agreement; (iv) the breach of any representation or warranty contained in this Agreement; or (v) the enforcement of this Agreement, including, without limitation, the cost of assessment, containment and/or removal of any and all Hazardous Substances from all or any portion of the Property or any surrounding areas, the cost of any actions taken in response to the presence, release or threat of release of any Hazardous Substances on, in, under or affecting any portion of the Property or any surrounding areas to prevent or minimize such release or threat of release so that it does not migrate or otherwise cause or threaten danger to present or future public health, safety, welfare or the environment, and costs incurred to comply with the Environmental Laws in connection with all or any portion of the Property or any surrounding areas. “ Costs ” as used in this Agreement shall also include (without double counting to the extent such diminution is already reflected in the costs covered above) any diminution in the value of the security afforded by the Property or any future reduction of the sales price of the Property by reason of any matter set forth in this Paragraph 1 ; provided, however, the costs attributable to diminution in value as described herein shall not exceed the outstanding indebtedness evidenced by the Note plus any costs incurred by Lender in disposing of the Property or the Loan and shall be payable if and only to the extent such diminution or reduction results in a damage or loss to Lender as a result of its inability to recover the outstanding indebtedness upon disposing of the Property or the Loan by Lender or an affiliated entity. The foregoing indemnity shall specifically not include any such costs relating to Hazardous Substances which are initially placed on, in or under the Property after foreclosure or

AMENDED AND RESTATED ENVIRONMENTAL AND HAZARDOUS SUBSTANCE

INDEMNIFICATION AGREEMENT - Page 2

43412-20/Continental Towers

other taking of title to the Property by Lender or its successors or assignee or a purchaser at a foreclosure or a grantee of a deed in lieu of foreclosure.

2.              Representations Regarding Hazardous Substances . Borrower hereby represents and warrants to and covenants and agrees with Lender as follows:

(a)            To the best of Borrower’s knowledge, information and belief, after due inquiry and investigation, and except as otherwise disclosed in the Phase I Report (as defined in the Security Instrument) the Property is not in violation of any Environmental Law;

(b)            To the best of Borrower’s knowledge, information and belief, after due inquiry and investigation, and except as otherwise disclosed in the Phase I Report (as defined in the Security Instrument) no Hazardous Substances are located on or have been handled, generated, stored, processed or disposed of on or released or discharged from the Property (including underground contamination) except for those substances used in the ordinary course of business and in compliance with all Environmental Laws;

(c)            The Property is not subject to any private or governmental lien or judicial or administrative notice or action relating to Hazardous Substances;

(d)            To the best of Borrower’s knowledge and belief, after due inquiry and investigation, and except as otherwise disclosed in the Phase I Report, there are no existing or closed underground storage tanks or other underground storage receptacles for Hazardous Substances on the Property;

(e)            Borrower has received no notice of, and to the best of Borrower’s knowledge and belief, there exists no investigation, action, proceeding or claim by any agency, authority or unit of government or by any third party which could result in any liability, penalty, sanction or judgment under any Environmental Laws with respect to any condition, use or operation of the Property nor does Borrower know of any basis for such a claim; and

(f)             Borrower has received no notice that, and to the best of Borrower’s knowledge and belief, there has been no claim by any party that, any use, operation or condition of the Property has caused any nuisance or any other liability or adverse condition on any other property nor does Borrower know of any basis for such a claim.

(a)            Borrower shall keep or cause the Property to be kept free from Hazardous Substances (except those substances used and stored by Borrower or any tenant of the Property in the ordinary course of its business and in compliance with all Environmental Laws and, if applicable, its Lease), shall not install or use any underground storage tanks, shall expressly prohibit the use, generation, handling, storage, production, processing and disposal of Hazardous Substances by all tenants of space in the Improvements (except

AMENDED AND RESTATED ENVIRONMENTAL AND HAZARDOUS SUBSTANCE

INDEMNIFICATION AGREEMENT - Page 3

43412-20/Continental Towers

those substances used in the ordinary course of business and in compliance with all Environmental Laws and its Lease), and, without limiting the generality of the foregoing, during the term of this Agreement, shall not install in the Improvements or permit to be installed in the Improvements asbestos or any substance containing asbestos.

(b)            Borrower shall promptly notify Lender should Borrower become aware of (i) any Hazardous Substances, or other potential environmental problem or liability, with respect to the Property, (ii) any lien, action or notice affecting the Property or Borrower resulting from any violation or alleged violation of the Environmental Law, (iii) the institution of any investigation, inquiry or proceeding concerning Borrower or the Property pursuant to any Environmental Law or otherwise relating to Hazardous Substances, or (iv) the discovery of any occurrence, condition or state of facts which would render any representation or warranty contained in this Agreement incorrect in any material respect if made at the time of such discovery. Borrower shall, promptly and when and as required and regardless of the source of the contamination, at their own expense, take all actions as shall be necessary or advisable for the clean-up of any and all portions of the Property or other affected property, including, without limitation, all investigative, monitoring, removal, containment and remedial actions in accordance with all applicable Environmental Laws (and in all events in a manner reasonably satisfactory to Lender), and shall further pay or cause to be paid, at no expense to Lender, all clean-up, administrative and enforcement costs of applicable governmental agencies which may be asserted against the Property. In the event Borrower fails to do so, Lender may, upon not less than ten (10) days prior written notice to Borrower, cause the Property or other affected property to be freed from any Hazardous Substances or otherwise brought into conformance with Environmental Laws and any reasonable out-of-pocket costs incurred in connection therewith shall be included in Costs and shall be paid by Borrower in accordance with the terms of Paragraph 4(c) hereof. In furtherance of the foregoing, Borrower hereby grants to Lender access to the Property and an irrevocable license to remove any items deemed by Lender to be Hazardous Substances and to do all things Lender shall reasonably deem necessary to bring the Property into conformance with Environmental Laws.

(c)            Upon the written request of Lender, at any time and from time to time after the occurrence of and during the continuance of an Event of Default under this Agreement or the Loan Documents or at such other time as Lender has determined (in the exercise of its good faith judgment but in no event more than one (1) time in any consecutive twelve (12) month period absent the occurrence and continuance of an Event of Default) that reasonable grounds exist to believe that Hazardous Substances are or have been released, stored or disposed of on or around the Property in violation of the Environmental Laws, Borrower shall provide, at Borrower’s sole expense, an inspection or audit of the Property prepared by a hydrogeologist or environmental engineer or other appropriate consultant reasonably approved by Lender indicating the presence or absence of Hazardous Substances on the Property in violation of Environmental Laws or an inspection or audit of the improvements located on the Property prepared by an engineering or consulting firm reasonably acceptable to Lender indicating the presence or

AMENDED AND RESTATED ENVIRONMENTAL AND HAZARDOUS SUBSTANCE

INDEMNIFICATION AGREEMENT - Page 4

43412-20/Continental Towers

absence of friable asbestos or substances containing asbestos on the Property. If Borrower fails to provide such inspection or audit within sixty (60) days after such written request, Lender may, upon not less than ten (10) days prior written notice to Borrower, order the same, and Borrower hereby grants to Lender access to the Property and an irrevocable license to undertake such inspection or audit. The cost of such inspection or audit shall be included in Costs and shall be paid by Borrower in accordance with the terms of Paragraph 4(c) hereof. If no Event of Default has occurred and is continuing and in the event Lender requests any such inspection or audit more than one (1) time in any consecutive twelve (12) month period, Lender shall have the right to obtain such additional audit or inspection at Lender’s sole cost and expense.

(i)             settle or compromise any act