The castle stands on a rocky outcrop overlooking the valley. It was the main fortress of the Grisonians and one of the largest castle fortifications in Switzerland. Built in the Dark Ages, in was extended in stages by the Sacco family (12th and early 14th centuries) and by Gian Giacomo Trivulzio (after 1480) and then dismantled by the Rhaetian Leagues in 1526. The most impressive remains, which underwent preservation work in 1925-26 and at the end of the 20th century, are those of the tower that was destroyed in the 19th century, possibly by lightening. At the foot of the rock archaeologists have found human remains dating back to the Mesolithic Period (around 7000 BC).