This is not just one museum, but several under one name. When visiting DC, make sure you visit these museums. There is the natural history museum, the art museum, air and space musuem...I can't remember all of them, but it is awesome. I love the museum with all the cool fossils, dinosaurs, rocks, etc. You could easily spend several days going through these museums. I think they are all free, but I'm not sure, since it has been a while since I've been here. Don't miss the zoo also, it is free!