The New York Earth Room is an interior sculpture by the artist Walter de Maria that has been installed in a loft at 141 Wooster Street since 1977. Go see!
You've heard about the reading room at the New York Public Library, haven't you? Then I need not go on. Just look at it. And you're allowed to hang around in there!
A street party/DJ sound system built out of a shipping container. A little slab of hungover berlin/pregaming Berlin in Brooklyn. Whomever the great DJs in town are you will find them playing a low-key set here for a crowd of less than 50 people. Sunset is magic as there's a straight shot through to Manhattan and the light is perfection.