The two rocky islands house what remains of the Vitaliana Fortress, which Ludovico Borromeo, the feudal land owner of Ivrea and Cannobbio, had built between 1519 and 1521, seem to blossom in the middle of the lake, not far from the banks. The fortress, one of the most suggestive spots in Piedmont, was built over the ruins of the Malpaga Fortress in order to defend the area of the Upper Lake Maggiore from Swiss raids. The main part, which is on the larger island, still has some of its massive wall that skims the water and several large towers of different shapes and still partially crenellated. On the smaller island, called "Prigioni" ("Prisons"), instead, a single broken tower and a wall that continues to flake away can be seen. The fortress, completely abandoned during the second half of the 17th century, gave refuge to traffickers, forgers, and fishermen, after which today – as Piero Chiara wrote in Fioriva una rosa (A Rose Bloomed) - only "ruins, broken steps, large rooms where fishermen hung their nets to dry..." remain.
