Luhring Augustine did a good job of converting an old warehouse/storage facility into a blue chip commercial art gallery that stages four shows of contemporary art per year. Which means you can catch museum quality shows in an unlikely spot, away from all the Chelsea pomp, and it actually has friendly staff, instead of a cold gallerina sat behind a desk pretending to be on the phone.
You can't say you've seen NYC until you've seen it from a boat. Hop on the ferry from anywhere to anywhere and you'll see what I mean. Not only will you see excellent old buildings and factories--the inner workings of the old industrial city--but you'll head out under working bridges and see the skyscrapers in all their towering glory. And once you've done it, do it again, at night.