I went to college in DC, and lived there for 12 years back in the 90s and 00s. There are some good suggestions in the thread. My personal ones:
-The Lincoln and Jefferson memorials are must sees. It is too bad you wont be there in Spring-Jefferson memorial and cherry blossoms is fantastic.
-The Smithsonian museums are all worth your time-especially Air and Space and American history.
-The White House tour is really good. The FBI building tour is also really great and interesting, if they still do it. You have to get tickets in advance, but it is really good.
-The National Zoo is great, but be careful about that if you are going in February. This could have changed since I was there, but it did not have many indoor places and there is a lot of walking. Not a great place if there is winter weather,
Have fun TC! I do not miss DC traffic, but other than that it is a pretty great place.
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