Sforza Castle stands on the site of the former fortifications of Castrum Portae Jovis from the time when Milan was the capital of the Roman Empire. It was here that the 'castra pretoria' - the personal bodyguards of the Roman emperors - were stationed in ancient times.
However, it was during the time of the Sforza family in Milan that the Castello Sforzesco rose to greatness. Some of the greatest artists of the Renaissance worked on its decoration: Leonardo da Vinci (who did the frescoes in several rooms, in collaboration with Bernardino Zenale and Bernardino Butinone) and Bramante.