United States Capitol dome

The United States Capitol features a dome situated above its rotunda. The dome is 288 feet (88 m) in height and 96 feet (29 m) in diameter.^[1] Designed by Thomas U. Walter, the fourth Architect of the Capitol, it was constructed between 1855 and 1866 at a cost of $1,047,291 (equivalent to $17.1 million in 2023).^[2][3] The Statue of Freedom tops the lantern on the dome, and the dome is centered over the origin on street maps of Washington, D.C.

The dome is not stone, but rather cast iron carefully painted to appear to be made of the same stone as the main capitol building. It is actually two domes, one inside the other, and the total weight is 9.1 million pounds (4,100 t).^[4] The dome's cast iron frame was supplied and constructed by the iron foundry Janes, Fowler, Kirtland & Co. in the Bronx, New York.^[5] The interior of the dome includes a detailed geometric and floral pattern of lightly colored plasterwork, with Brumidi's monumental ceiling fresco, The Apotheosis of Washington, appearing in the oculus at the top of the inner dome.