There are some great museums and cultural opportunities there. I'm firmly of the opinion that everybody ought to spend two, maybe three weeks in DC. Go to the Smithsonian, the monuments, see the Capitol and White House...then turn in any direction and run, don't walk, away.
That would be the Steven F. Udvar-Hazy Center at Dulles, an extension of the Smithsonian Air & Space Museum. From what I've heard, you can take a full day in each of their two hangars and still be left wanting more (plus a day at the main A&S Museum, or course).
I want to visit there one time. When my wife retires next year early, we are planning on taking our RV on the road for an extended road trip. I DO want to visit DC for the memorials, and museums. My wife is not a huge museum fan, so will have to work around that.
