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!
I love enjoying some Amazing Vietnamese food at this place before heading out to the different bars around Jefferson on L. The restaurant is just behind Elsewhere so you have a nice mix of things to do if you start your night here.
Mcgolrick Park at midnight in the snow. Any early morning with all the bums and drunks passed out on Nassau Avenue. NYC still looks best between 3am and 6am, just before the light comes in to shine on all its flaws.