What today remains of the old Sforzesco Castle is only a part of the original building restored by the Sforza family after the Milanese citizens had destroyed the Visconti Castle in 1447. At present, the Castle is a quadrilateral enclosing the PIAZZA DELLE ARMI, with its central tower facing the city designed by Filarete and later restored by Luca Beltrami and two cylindrical towers covered with bosses on each side (the TORRIONE DEI CARMINI and TORRIONE DI SANTO SPIRITO). At the beginning of the 20th century, some new buildings, which now house offices, were added to the walls facing south and west. The TORRE DI BONA DI SAVOIA is built on one side of the Rocchetta, just near the place where there was the old PORTA GIOVIA, one of the medieval gates providing access to the city. The FOSSATO MORTO (dead moat), which can be seen today around the inner walls of the castle, was the original moat around the medieval town walls.