During the Lombards era the monastery of San Pietro in Ciel d'Oro in Pavia possessed a farm in Magliaso. The origin of the old church of S. Quirico (mentioned in 1033) and the San Giorgio Castle is not known. It was the home for nearly two decades (1098–1117) for the schismatic bishop of Como, Landolfo Carcano, who was appointed by Emperor Henry IV against Pope Gregory VII's bishop. The castle was besieged and conquered in 1117 by Como and the fate of Landolfo, is uncertain (possibly deported or murdered). This caused the ten-year war between Como and Milan. The romanesque fresco on the south tower dates from around the same time and is one of the few secular romanesque works in Switzerland. In the 13th Century the castle passed into the possession of a branch of the Rusca family of Como. Carlo Corrado Beroldingen, Chancellor of the bailiwick of Lugano, acquired the sovereign rights over the village in 1668. He had the parish church built and replaced the decaying ruins of the castle with an ornate palace.