The castle was equipped with two moats: one dividing the Courtyard of Arms from the Ducal Courtyard and the Rocchetta, now referred to as the dead moat; and the original moat that defended the city walls when the Visconti Castle was under construction. The moat outside the fortress, purportedly of the Sforza era, was filled-in in the 17th century and re-excavated between the 19th and 20th centuries.