Built as a fortress in the 13th century by the Marquis of Monferrato Guglielmo VII. Two Roman towers from the ancient "Porta Pretoria" were incorporated into the building. In the 15th century it was expanded by Ludovico d'Acaja, with the construction of the façade facing the Po River, and during the 17th century Ascanio Vitozzi and Carlo di Castellamonte readapted it. The monumental baroque façade was built between 1718 and 1721; the design by Filippo Juvarra, was carried out only partially. It is characterized by a giant order of pilasters and Corinthian fluted columns, surmounted by a marble balustrade with reliefs, statues and vases. Inside, the monumental ceremonial staircase by Juvarra is of interest. The Civic Museum of Antique Art, with its rich collections of sculptures, paintings, glass panes, tapestries, etc., is housed inside the palace.