The Hirshorn Museum is a a Smithsonian museum of modern art and sculpture. It is shaped like a hollow cylinder and has a sculpture garden at front. When will it no longer be modern?
10 years after people: A flood washes away some sculptures, but not others. The museum itself loses some footing, but can still stand.
20 years after people: Another flood sweeps in and takes away most of the sculptures. The basement gallery is harmed the most.The Wish Tree from Yoko Ono dies.
25 years after people: The legs of the museum cannot hold the brunt anymore and give out. The basement is obliterated. A few sculptures remain, but they will go down too.