United States Capitol rotunda
The United States Capitol rotunda is the central rotunda of the United States Capitol in Washington, D.C.. It was built 1818–1824. It is located below the Capitol dome, built 1857–1866. It is the tallest part of the Capitol and has been described as its "symbolic and physical heart".
The rotunda is 96 feet (29 m) in diameter, rises 48 feet (15 m) to the top of its original walls and 180 feet 3 inches (54.94 m).