The Castle, including a fewdwellings (castrum), stands on Mount Fluno. It has a trapezoidal plan, with the eastern and western sides longer than those of the north and south. A number of round towers are incorporated in its curtain wall with Guelph merlon battlements, especially along the western and southern sides, while a square tower (Mastio) serves as the entrance to the castle on the northern side. One of the round towers was made into a bell tower in the 15th century. Inside the Castle you can admire the remains of the Church of San Lorenzo Martyr, protector of the plague-stricken, where you can still see fragments of a medieval fresco from the 1300s that used to cover the apse and which depicts Christ with the evangelists Mark and John.