The Senate Chamber is a rectangular, two-story room located in the center of the north wing. The nation's 100 senators sit at individual desks arranged on a tiered semicircular platform facing a raised rostrum. A visitor's gallery overlooks the chamber on four sides.
First used on January 4, 1859, the Senate chamber was designed by Thomas U. Walter, the architect of the Capitol extension. The chamber was built without windows to insulate senators from outside noise. Light was originally provided through a large skylight and ventilation came courtesy of steam-powered fans.
In 1949-1950 the chamber was reconstructed, the skylight removed, and the walls redesigned. Pilasters made from red Levanto marble replaced the cast-iron originals; the wooden rostrum was replaced with a larger version in marble; and the iron and glass ceiling was taken out and a new stainless steel and plaster ceiling installed. The alteration were intended to improve the chamber's acoustics and ventilation while ridding it of its mid 19th-century decor, which was then out of fashion.