In furtherance of the general purposes of this subchapter as prescribed in section 407m of this title, the Secretary of the Interior is authorized to enter into cooperative agreements with the city of Philadelphia to assist in the preservation and interpretation of the property known as the Independence Hall National Historic Site and with the Carpenters' Company of Philadelphia to assist in the preservation and interpretation of Carpenters' Hall, in connection with the Independence National Historical Park. Such agreements shall contain, but shall not be limited to, provisions that the Secretary of the Interior, through the National Park Service, shall have right of access at all reasonable times to all public portions of the property now within Independence Hall National Historic Site and to Carpenters' Hall for the purpose of conducting visitors through such buildings and grounds and interpreting them to the public, that no changes or alterations shall be made in the property within the Independence Hall National Historic Site, including its buildings and grounds, or in Carpenters' Hall, except by mutual agreement between the Secretary of the Interior and the other parties to the contracts.