In 1325 Galeazzo I Visconti, who conquered the city after a long siege, began the construction of new defences. Among the projects was the bifurcation of the River Lambro (the "Lambretto" branch) and the construction of a castle, the third in Monza. It included a tall-tower, later used as a jail ("Forni"). The Castle of Monza was later expanded to such a degree that it was necessary to demolish the St. Mary of Ingino church as space was needed for new buildings. Two other towers were also built along the River Lambro. In 1327 Galeazzo himself was imprisoned in the "Forni", by order of emperor Louis IV. He was released the next year.