Sure, the giant white dome of the Capitol is the symbol of representative democracy, but it also makes for a great (and free) tour. You'll learn the rich history of the building and see the ornate grandeur inside, in striking contrast to the Neoclassical restraint of its exterior. But the greatest thrills here come from the electric buzz of power: the statesmen striding confidently through the halls are Washington's rock stars. When Congress is in session, you can watch your elected reps in action from the House or Senate gallery. For instructions on how to get passes, call the Capitol switchboard at (202)224-3121.
Admission: Free, with timed ticket from kiosk below the Capitol, near Independence Avenue. (A timed ticket allows entrance at a predetermined time.)