Surprised nobody posted the Woolworth Building yet.
I snuck up there pre-9/11. (Incredibly easy, nobody even asked what I was doing) and went up to the old OBS deck. The floor below it (you take some stairs to get to the OBS deck was pretty small, but perfectly sized for a condo.
In fact, pre-9/11 you could walk into most lobbies and pre-1993 WTC bombing you could walk into EVERY lobby and about 80% of the time (that I tried) just get on an elevator.
Good times... I miss my teen years.