What's to see and do in Washington DC?

[Doctor Strange]

As others have said, it's punishingly hot and humid in the summer, but Washington is still awesome. Every museum on the National Mall is worth visiting - American History, Air and Space, Natural History, both buildings of the National Gallery, the other art museums... and admission to nearly all of them (being components of the Smithsonian Institution) is FREE. And if it's not too uncomfortable outside, the memorials - Lincoln, Jefferson, FDR, Korean war, Vietnam, WWII, etc. - are all inspiring and memorable. Just walking around, there are fascinating buildings and statues everywhere. Union Station is an Art Nouveu beauty, the Capitol, Library of Congress, and Supreme Court buildings are so impressive...

And it wasn't open yet the last time I was there, but I'll bet the Spy Museum is fascinating.

I've been on multi-day visits to Washington four times, and didn't come close to seeing everything!

 

[scotrace]

See everything you can - there's little that isn't of interest. A much easier list might be what you really do NOT want to see.

I'm thinking that, as you are coming from London, you aren't going to be as bowled over by swell buildings, you might want to concentrate on spots that illustrate the split, and the origins of our country. If you can, get out to Mt. Vernon, General Washington's home, which is remarkable for its simple elegance. See the Smithsonian of course. The Lincoln, WWII, FDR memorials. Shopping: Georgetown!
Getting about, the trains are clean, easy to understand, cheap, frequent, safe and fast. DC is run by Congress, and they want the folks from back home to see their governmental seat in the best light. You're used to London, so DC should seem as safe as Bullfrog, North Dakota.

Weather: Historically, Washington clears out in the hot summer months. Lincoln used a summer house (preserved) not too far out of town, but far enough to escape the worst of the swampy swelter. It's going to be hot and humid. Washington used to be plagued by malaria.

I'll echo what Rue said about the Willard. The current structure isn't technically historic, as the place had multiple burn-downs and has been rebuilt. Everyone stayed at The Willard. It's the one place I would never miss seeing. I once had drinks there with Fred H and his stunningly beautiful wife, and Barbigirl. It was a highlight of my life. The Willard is a monument to Victorian gimcrackery.