Phoebe and I went to the National Gallery of Art, which I always forget is not a part of the Smithsonian. But it's also a free museum and it's amazing. Today we checked out the modern art building.
This underground walkway connects the two galleries. The lights flow and change in very cool ways. Not worth explaining. Gotta see it yourself.
Sol Lewitt is awesome. This wall is completely covered with colored pencil lines (see close up just below). The wall is probably about 20'x30' or a bit more.
One of Andy Goldsworthy's rock installations. It's on both sides of the window.
This is more typical of Sol Lewitt. My friend Ryan and I have had kids recreate some of his work in our Geometry classes. Ryan even had some students paint their final product on the wall in the hallway above his door, also incorporating the famous 4 color problem in mathematics. 
