United States Capitol dome (largest cast-iron dome in the world)

The cast-iron dome of the United States Capitol, designed by Thomas U. Walter and constructed between 1855 and 1866, is the largest cast-iron dome in the world. It rises to approximately 288 feet above the ground to the top of the Statue of Freedom. The dome replaced an earlier, smaller wooden dome and was completed during the American Civil War using cast-iron sections manufactured off-site and assembled on the building. The Capitol dome remains a prominent architectural and engineering landmark in Washington, D.C.