This room is not particularly large, but it is an important symbol in the history of the Republic: here Enrico De Nicola, Alcide Degasperi and Umberto Terracini signed the Italian Constitution on 27^th December 1947, as appears in the photograph under a planisphere on one of the walls. On the other walls there are a map with the territories conquered by Rome and a view of the imperial city.

A copy of the Constitution rests on a bookstand. The Renaissance-style table is the same one on which the Constitution was signed. Now it is used by the Senate President to meet Heads of State and Government.

The most outstanding feature of the room is a high wooden bookcase, with a balcony and a winding staircase to reach the highest shelves.