The palace is located on the site of the Fortezza Augustana, residence of the leader Castruccio Castracani, where his palace was also, perhaps designed by Giotto. The large complex, which occupied about a fifth of the city, was destroyed by the population in 1370. The fortress was restored and used as a residence by Paolo Guinigi in 1401; after its fall in 1429 it was once again dismantled and later became the Palazzo Pubblico.