I might find myself with a 1.5 day layover at D.C. Land at 5 am at Dulles on Saturday morning then depart early Sunday afternoon. About five years ago I toured the Air & Space Museum and thought that was fantastic. Looking forward to touring the museum next to Dulles on Sunday morning to see all the planes they have there. Give me some ideas on what to do Saturday around the Mall. No car and I will be spending the night at a Hampton Inn about 7 blocks from the National Archieves.
Spent a week there last year. If I had to do just one thing, it would be: arrive by cab at the Lincoln Memorial at 7am or a little before. You will have it to yourself. Stand before the statue, read the Gettysburg address on the left wall, the 2nd inaugural on the right, and , turn and face the mall, the famous pool of so many events from MLK to Forrest Gump. Anyway, it really got to me. Then as the first bus arrives, head down the steps and up the mall. Viet Nam memorial on your left, then Korean on your right, then the WW2 way up near the middle. Take your time, think about it. Then to the Washington Monument and you're iout of the trees and in the clear. This will take a couple of hours to do, overall. Having got that in, pick your poison of the mall museums. Archives are cool, but, not all that much. I like the National Museum of Art, but, that's not for everyone. Head up to Grand Central Station for a glimpse of how it used to be, in the grand age of trains, etc. And walk around the Capitol Bldg. Can't get near it or on the steps or anything, which is too bad, but then its a great view all the way back down the mall. You'll have a huge apetite and sore legs after this. You always get sore legs in DC.
sorry I didn't see this before you went, but for future reference, check out the spy museum...most fun I had during a 5 day trip to D.C. was at that museum.
My favorite museum is the Air and Space but my favorite experience was the Lincoln Memorial at night.
National Geographic has or had a museum of the weird on 16th, a few blocks up from the White House. That was always nice and not very crowded. I lived a little bit up the road from it and frequented it a good amount. I also prefer the Gallery of Art to Air and Space but that may be due to the crowds and having seen it a lot early on in my living there. If you like sculptures I suggest the Hirshorn on the Mall as well. You can ice skate next to the Gallery of Art too. Too bad you won't be there for longer or I would have you travel to Dumbarton area in upper Georgetown, East of Wisconsin Ave. I also lived across the street from the park, near the cemetery edge and it is gorgeous. The park and the little museum with a good amount of Olmec, Mayan and some Teotihuacan pieces as well.