the library of congress: look something up, or just look up
From the monuments and memorials to its great civic and government buildings, DC is full of amazing architecture, but in my opinion the city has two absolute gems - places where I can get lost standing still. One is the Library of Congress - this is just the foyer! Next time I'm in town I'll try to get a shot of the main reading room - and my other favorite structure, the National Cathedral.
Someone has turned this photo into a pretty fun puzzle, which can be found here.