Palazzo Giustiniani, Senate residence near Pantheon, Rome, Italy

Palazzo Giustiniani is a palace on Via della Dogana Vecchia in Rome's Sant'Eustachio district, near the Pantheon. Its tall orange facade rises from a pale stone base to a projecting cornice, with rectangular windows framed in pale stone, grey-green shutters on the upper floors and dark metal grilles at ground level. A rounded stone portal carries a small balcony with a dark iron railing, the off-centre doorway and balcony added by Francesco Borromini in 1650.

Palazzo Giustiniani was built at the end of the 16th century for Monsignor Francesco Vento and bought in 1590 by Giuseppe Giustiniani, a Genoese noble whose family had governed Chios. His son Cardinal Benedetto Giustiniani joined neighbouring buildings until the palace covered a whole block near the Pantheon. Giovanni Fontana designed it, probably with his brother Domenico; in 1650 Francesco Borromini added the off-centre doorway with its balcony on Via della Dogana Vecchia and the courtyard with lowered arches.

The name recalls the Giustiniani family from Genoa, who once owned the property and built their private art collection here. Today the building serves as an extension of the Senate, where officials and staff carry out their duties while the historic halls are used for ceremonial occasions.

An underground passage links the building to Palazzo Madama across the street, where the Senate holds its sessions. Access is only possible on certain occasions and with prior permission, as the building continues to serve political purposes.

The room where the Constitution was signed is the Sala della Costituzione, not the library; the Italian source places the 27 December 1947 signature there, by Enrico De Nicola, Alcide De Gasperi, Umberto Terracini and Giuseppe Grassi. The Sala Zuccari, named after Federico Zuccari, keeps its 1586–87 ceiling frescoes of the story of Solomon.