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                                                                   Exhibit 3.124

                            CERTIFICATE OF FORMATION

                                       OF

                        AGH 75 Arlington Heights LLC

     The undersigned, an authorized natural person, for the purpose of forming a
limited liability company, under the provisions and subject to the requirements
of the State of Delaware (particularly Chapter 18, Title 6 Del.C. Section
18-101, et seq. hereby certifies that:

     FIRST. The name of the limited liability company (hereinafter called the
"limited liability company") is AGH 75 Arlington Heights LLC.

     SECOND. The address of the registered office of the limited liability
company in the State of Delaware is c/o Corporation Trust Center, 1209 Orange
Street, in the City of Wilmington, in the County of New Castle, Delaware, 19801.

     THIRD. The name and address of the registered agent for service of process
on the limited liability company in the State of Delaware is The Corporation
Trust Company, Corporation Trust Center, 1209 Orange Street, in the City of
Wilmington, in the County of New Castle, Delaware, 19801.

     IN WITNESS WHEREOF, the undersigned has executed this Certificate of
Formation as of this 11th day of February, 1997.


                                        /s/ Elizabeth M. Bush
                                        --------------------------
                                        Name: Elizabeth M. Bush
                                        Authorized Person