Complex sentence: The Downtown Athletic Club clubhouse was not physically damaged in the attack on 9/11/01, but it was located within the "frozen zone" from which the public was excluded for an extended period during the clean-up after the attack.
Split into simpler sentences: The Downtown Athletic Club clubhouse was not physically damaged in the attack on 9/11/01. But it was located within the "frozen zone" from which the public was excluded for an extended period during the clean-up after the attack.