Placed on a hill overlooking the town, the castle was built in late Middle Ages to block the way to Valvarrone and it still remains a well-preserved tower, surrounded by ruins of ancient houses. The first proofs date back to 1039, when it suffered a long siege. In the Mai district, on the headland overlooking the southern part of Dervio, there are still the ruins of an old castle named Castelvedro from the 5th and 6th century. The fort is situated in a dominant position and it was part of the defense system created on the shores of the lake against the raids of the barbarians from Rezia. It was used to control the old road which connected Dervio with Piazzo di Casargo at the entrance of Valsassina.