The St. Antony Church became the seat of the Chair Bishop of Ampurias in 1503. The current factory is derived from reconstructions operated between 1597 and the eighteenth century. The building, which blends elements of Catalan Gothic and Renaissance classicism, is located in the historical center of Castelsardo, in a panoramic position overlooking the sea. Externally it is characterized by the high bell tower covered with a tiled dome. The interior, with a Latin cross plant, consists of a single nave with a barrel vault, side chapels and transept painted by Andrea Lusso, the Mannerist painter best known in Sardinia. The apse, with starry vault, is rectangular in plant and houses the marble high altar (1810), in which dominates the painting of the Enthroned Madonna and Child (XV century). Also interesting are some wooden altars and eighteenth-century organ. Numerous works of art can also be seen in the basement of the Cathedral, used as Diocesan Museum.