While I am local, I find this forum the be very informative. I often have guests in town and they have seen all the standard tourist sites (musuems and monuments). Next time they are in town I'd like to send them to some"hidden gems". Some of the places I can think of are:
Library of Congress - http://www.loc.gov/loc/visit/
Great rotating exhibits. Fantastic architecture.
One of my personal faves. Gotta get the tour !! The Museum was designed in the 1880s by Montgomery C. Meigs to house the Pension Bureau. The building's exterior dimensions are 400 feet by 200 feet, and 75 feet high to cornice level. The rotating exhibits are interesting and are related to architecture, design, engineering, construction, and urban planning.
Botanical Gardens - http://www.usbg.gov/
Gravelly Point - …aol.com/washington/entertainment/venue.adp…
If you like planes you will love this place. This park sits on the Virginia side of the Potomac right at the end of the runway for National Airport. Every few minutes a plane SCREAMS overhead to land or take off (depending on which way the wind blows)
So, posters... what are you hidden gems for tourists???