A car will be a hassle in
Washington DC for many visitors also you don’t get parking in many of the places, so public transport is a good option to visit many places including
The Lincoln Memorial, and the
international spy museum, and the
Air and Space Museum. The Space Museum and the International Spy Museum could both take up several hours so you may want to choose either one to visit. If you want to visit Washington Monument, then purchase your tickets on-line in advance to save time there. Hope this helps and have a nice trip!