The Smithsonian Museums and National Zoo are all free. Please note, the African American History and Culture Museum, the Air and Space Museum, and the Nationnal Zoo all require timed entry passes that you should reserve in advance. Check out the Smithsonian website for more details.
The Capitol Visitor Center is open Monday-Saturday from 8:30 a.m.-4:30 p.m. All tours are led by professional tour guides and visit the Crypt, the Rotunda and National Statuary Hall. The tour route is subject to change. The tour does not include the Senate and House Galleries. Reservations are recommended, but not required.