The castle occupies the ancient site of Comum Oppidum, the original settlement of Como, dating from the 1st millennium BC. Later it was one of the last Byzantine strongholds in the area, surrendering to the Lombards in 588. The castle was restored during the War of the Lombard League, with the help of emperor Frederick Barbarossa (1158). Barbarossa officially donated it to the citizens of Como in 1178.