The Senate Chamber, designed by Luigi Gabet, occupies the former courtyard of the old papal Post Office.

In the 1930's, the galleries of the members of the Chamber of Deputies and Diplomatic Corps, supported by pillars rising from the floor, were replaced by overhanging galleries at a higher level. Other alterations were also made to the middle aisle to increase the number of seats, but the original structure and the decorations in this room have remained practically unchanged.

The ceiling is the work of little-known artists (Fumanti, Nava, Bruschi, Mei, Barilli and Gai) and features symbolic representations of Strength, Justice, Concord and Law.