My favorite museum on the Mall is the Hirshorn, directly across from the Air and Space place. The exterior looks a bit like a space vehicle.
During the summer months the fountain is running, but I think it's just as interesting in the winter. This is where the fisheye lens comes in handy.
The featured exhibit at the Hirshorn is a collection of Morris Lewis works. He used a thin acrylic called Magna and drew it across the canvas to make some compelling paintings.
Downstairs, there is a coathanger sculpture by Dan Steinhilber.
For my Canadian friend, this is the building where all those screwy American laws are made. We call it the Capitol. Last year, they cleaned the exterior. Maybe soon they'll clean up the inside?