 At that period the town had developed alongside the left bank of the main branch of the river, whose course in that point opened eastward to form a vast delta.Water provided places, suburbs and the town itself with the most effective protection.Not very long before the construction of the Castle, the watchtower underwent a transformation, ordered by Nicolò II and probably carried out by the same Bartolino da Novara, who would both later have been the future patron and architect of the Castle.