Second perhaps only to the White House as the most recognizable building in Washington DC, the Capitol Building sits on a hill at the easternmost edge of the National Mall. The cast-iron dome atop the Neo-Classical building-built in 1793 on designs by William Thornton and with a cornerstone laid by George Washington-has a female statue at its pinnacle. This is a professional government building, with both the Senate and House of Representatives in residence, and with advacne planning you may be able to view a live debate from the visitor's gallery. Tours may be booked in advance online. Closed holidays.