Washington DC is a great place to visit for its museums and iconic images. If you have two days I would visit the following.
1. Walk past the White House
2. Once the lift is fixed pre-book the Washington Monument
3. Walk to the Lincoln Memorial
4. Return via the Vietnam Memorial
5. Visit the Air and Space Museum and follow the free tour at 10:30
6. Pre book a visit to the Capitol Hill tour. TAKE YOUR PASSPORT to allow further access to the Senate and Congress
7. Visit the Library of Congress and do the tour... this is a hidden gem!
8. Visit the US Holocaust Memorial is a must
9. The National Gallery of Art is also so very very impressive
10. If you can make it to the airport and the Air and Space museum there it is the best.
I am sure there are other great things to do in Washington DC but I ran out of time! Enjoy