I saw an episode of the History Channel’s Life After People series. Interestingly the older buildings, those built prior to WWII i.e. The Empire State Building and the Chrystler Building will last longer than post WWII structures. This is for two main reasons: The newer buildings suffer more water damage, and the structure of the newer buildings are designed with an inner core, which makes the outer skin more vulnerable to breakages faster. Also, the St. Louis Arch is theorized to be one of the longest lasting structures due to its stainless steel exterior.