Where: 5 Beekman St.
5 Beekman Street was built in 1882 and is the earliest surviving "fireproof" office building of the pre-skyscraper period. It features a gorgeous atrium and cast iron details, mosaic floors, and spectacular views. It's hard to find any abandoned buildings in Manhattan, so this palace is a hidden treasure. Apparently there are plans to rennovate the building, so you should get there before the real estate agents do!