National Constitution Center

This whiz-bang museum makes the US Constitution jump off the page, starting with a dramatic theater-in-the-round presentation by a single actor relating the evolution of the American project. This is followed by a dizzying array of interactive exhibits, from voting booths to trivia games. You can also see an original version of the Bill of Rights and be sworn in as president. Go early, both for lighter crowds and a fresher brain – this place is hard to skim through.