The U.S. Capitol is perhaps the most recognizable symbol of the United States of America.  First completed in the early 1800s, the distinctive, cast-iron dome was added in the mid 1800s.   Within the Capitol's 175,000 square feet of space are both chambers of Congress, grand halls, numerous offices, and a $600 million Visitors Center, a massive underground complex which opened in 2008.  Built on Jenkins Hill, the Capitol overlooks numerous government office buildings below (enjoy your own metaphor here).