The Library of Congress
The Library of Congress turned out to be a real highlight of my visit to DC. Stunning architecture, well laid out exhibits (with computer UIs that worked and made sense!) and a general feeling of respect and a calm that was a very pleasant transition from the bustle and noise of the very heavily toured Capitol.
Ever since I was very small and watched the Reading Rainbow episode on the LoC, I've wanted to see the reading room. We didn't make it in there this time, but I'm definitely putting it on the list for next time.