The Dilapidated Octagon Tower on Roosevelt Island, New York before the renovations of 2006. It is now an apartment with 500 units.
This was originally the entrance to the New York City Lunatic Asylum which opened in 1841. This Octagon Tower was the last remaining bit of the Asylum but after years of decay and 2 fires it was closed to ruin.
Mistreatment of the patients was later reported from Nellie Bly in her 1887 book, where she faked insanity to study a mental health institution from within.
The second photograph is from May 1970.