I took a couple of days off last week. I did a little road trip to Virginia to see my parents. And... I visited the Smithsonian Air and Space Museum annex near Dulles Airport. At the Udvar-Hazy Center, they have a lot of items that are too big to store at the regular museum on the mall... like the Space Shuttle Discovery and the Enola Gay. The space shuttle is a BIG display. See scale below!
If you are a fan of planes, aviation history and motors, this is the place to visit. The parking fee is $15 per car, but it's free to get into the museum.
If you want to visit DC and stay closer to the Mall, make sure you stay until dusk to see the Washington Monument. It's under construction to repair damage caused by the 2011 earthquake, but it's cool when it's all LIT UP.