If you're going to visit one place on your Washington DC tour, we suggest the National Mall. Located right in the middle of the city, the National Mall houses some of the most interesting monuments, buildings, and museums in Washington.
We might be a little biased here, but we think the best way is to take a Washington monuments tour like the one offered by Action Tour Guide!
Are there tours of the Washington Monument? There are no guided Washington Monument tours inside the building, but you can reserve tickets to visit and check out the exhibits on their website