This is really the kind of museum that you want to make a whole day out of. Admission on the weekend requires a pass, but otherwise you can get in anytime after 10 am on weekdays. It's intense, but worth the visit.
Great food court, beautiful artwork, meaningful and intense exhibits
All the Smithsonian museums are free, so why not visit one of the best zoos in the US? This is a great activity for families and individuals alike.
A fun restaurant where you can check out board games to play while you enjoy your meal.
A DC institution, enjoy a chili dog and take in a DC staple.
Just outside of DC (you can take the Metro there) is Arlington National Cemetery. Visit John F. Kennedy's gravesite, the Tomb of the Unknown Soldier, and see the Changing of the Guard .
A bit farther out from the city is George Washington's Mount Vernon. It's a great activity for a nice day when you can walk the grounds and enjoy the great views.
Accessible by car or a short walk from the Rosslyn Metro. The island is in the Potomac river and offers a series of trails with city views.
The first week of May you should be able to see early rhododendrons and azaleas blooming, as well as flowering dogwoods, crabapples, late-flowering cherries, and Asian magnolia.
Rock Creek Park is another great place for a nature walk. The urban forest is located in the middle of the city and offers a series of trails and recreation areas.
Of course, you can't come to DC and not walk the National Mall. Visit the National Mall and Memorial Park website to help map out the monuments and memorial sites.