Oh, nomoo...if you go to District of COLOMBIA, you might not make it back. (Just joking with you.) Actually, it's the District of Columbia; and I think the greatest place for anyone to visit is the Smithsonian if you have time. (You can spend a month there and not see all the neat exhibits.) If you're on a whirlwind trip though try to see the White House and the Capitol and some of the great statuaries on the Mall. The War Memorials (all of them) are special, too.
In springtime it is all the cherry blossom trees in bloom. Otherwise, the Holocaust Museum and smithsonian museums. Also the metro, and a giant sculpture called "the awakening". It was in a park but I am not sure where they move it to.