The Museum of Modern Art and the Guggenheim Museum in NYC are probably must see for people really into art. I personally don't like contemporary and modern art a whole lot, and I find hard to understand plain photos of a painting, as if it was for a catalogue.
I found myself idling around all the masterpieces at these two museums while the rest of the group was avidly consuming the artifacts and I realized that some of them can actually be part of a picture, without being the sole subject.
People were the best complement to the various pieces of art, whether they are casually walking by, or they are deeply into the observation of a work.
In some cases the architecture of the place, as the astonishing Guggenheim, provides an interesting setting for a picture.