The isle is the only one in the Lake Orta and belongs to the municipality of Orta San Giulio. Probably inhabited since the Iron age, the isle has been considered a strategic site since VI century and thus surrounded by defensive walls. After having been a stage for the rivalry between the Sacred Roman Empire and the Lombard kingdom in the 10th century, the whole lake district was ceased to the bishops of Novara, who reconstructed on the island the cathedral of San Giulio in a Romanesque style. In 1841, the medieval castle was demolished to make room to a Seminary, designed by architect Ferdinando Caronesi.