7. Arlington National Cemetery. To reach Arlington, you will need to cross the Potomac, but it's still very close to downtown DC. Catch one of the complementary shuttle buses from the visitor center if you wish. It is an uphill walk if you decide to do it by foot. You will see rows of stones that will remind you of soldiers standing at attention. Also found at Arlington will be the resting places of the Kennedy family including JFK, Jackie, Robert, and John, Jr. There is an eternal flame at the former president's resting place.
Be sure to wait for the changing of the guard at the Tomb of the Unknowns and look for the many special monuments here such as a memorial to the astronauts of the Challenger and a memorial to the lives lost on Pan Am Flight 103 (Lockerbie, Scotland). Arlington House found on these grounds was the home of General Robert E. Lee. The Washington Monument can be seen from Arlington and view is quite impressive.
8. The Pentagon is in Arlington, VA, but like the cemetery is just a short distance from the city. This is a walking tour that will last an hour and a half, so be prepared with the footwear you choose as well as remembering the security issues. These include needing a valid photo ID for ages 16 and over and you will need to be scanned for security purposes. No cameras, tape recorders, video cams, etc. are allowed inside of the Pentagon.
9. The National Zoo on Connecticut Avenue is yet another spot that offers "nightmare level to non-existent" parking, so once again I will say that it is vital to research before your trip. Know which metro stops are for which attractions and your vacation will be a lot less stressful. The zoo is situated on more than 160 acres and houses about three thousand animals.
10. The National Cathedral. I won't try to think of too many words to describe this incredible building, but "awe-inspiring" "breathtaking" come to mind immediately. If you have a moment to visit the Cathedral and are near Massachusetts and Wisconsin Avenues, NW, it is certainly worth the visit. There are 215 exquisite stained glass windows and the tower rises 30 stories in height.