The annual contemporary art super-fair (with its Modern outgrowth directly to the south at Pier 92) features hundreds of galleries from all over the world presenting works by their artists. You probably need all four days to do it right; you'll saturate fast if you try to do it all in one visit. Look for the galleries that give their entire booth over to an installation by one artist, as they tend to be the most interesting and memorable when the dust settles.