The new plan was carried out by architect Carlo Sada who built an amphitheatre accomodating the Deputies' benches, the Chairman's and Secretaries' seats, the speakers' rostrum and the ministers' table.

The Deputies, who numbered 204 in 1848, met in this hall till April 18, 1860 (?) when the annexation of Lombardy, Emilia and Tuscany increased their number to 337. Following further annexations of central and southern regions, Deputies totalled 443 and Amedeo Peyron (1785-1870) was commissioned to plan temporary quarters. A new hall was swiftly erected in the courtyard of Palazzo Carignano and inaugurated on February 18, 1861. Made of wood, iron, and glass, the hall could accomodate up to one thousand people. Construction of permanent quarters for the Italian Parliament began on the Palace's premises in 1864, but such quarters were never used in their intended capacity because in that very year Italy's capital was transferred to Florence.

The Parliament Hall is evocative of the historical events it witnessed: tri-coloured cockades mark the seats of Camillo Cavour, Massimo d'Azeglio, Giuseppe Garibaldi, Cesare Balbo, Vincenzo Gioberti, and other famous political figures of the time.

Of great architectural interest is its lowered-arch dome topped by a skylight surrounded by seven false niches containing the escutcheons of several Italian and Savoy cities. Another seventeen escutcheons representing the provinces of the Kingdom of Sardinia are displayed on the balcony that encircles the amphitheatre, at the feet of the dome. They were placed there after their original destination, the hall built in the courtyard, was demolished.

Natural lighting is provided by the central skylight, whereas artificial light comes from eight large gilded-bronze wall-lamps, which may have been fuelled by gas.

Also interesting is the canvas behind the Presidency's table, painted by C. Felice Biscarra (1825-1894) and portraying king Vittorio Emanuele II. It is surmounted by a plaster relief by Giuseppe Dini (1820-1890) depicting the signature of king Carlo Alberto's Statute. The press gallery and the galleries for ladies and political observers could be reached through a small spiral staircase, whereas guests were seated on the balcony. The whole complex was restored in 1988, on the140th anniversary of the Subalpine Parliament. All the original furnishings, frescoes, decorations and even lighting were thoroughly repaired to make the hall look exactly as it did when it hosted the last Parliament session on December 18, 1860.