I was reminded again how impermanent most human things are in this world, looking at the various parts of the Empire State Plaza platform that are all torn up to replace leaky roofs under the planters, grass and concrete slabs, to limit water and salt intrusion into the building where it can deteriorate the concrete by causing the rebar to rust and the concrete to spall. Without constant maintance of the Plaza the concrete would quickly deteriorated over a period of a few years. 50 or 100 years after abandonment, there might not be much more then pile of collapsed concrete concrete rubble and rusty piers with trees and bushes all grown over it.