Imposing fortress that occupies the entirety of the Monte Boi peninsula (18 hectares), surrounded by three kilometers of walls. It has three main towers: the Torre do Relógio (Clock Tower, at the entrance, with an alarm bell), the Torre de la Tenaza (Tenaille Tower, to the east, defending the port with artillery), and the Torre del Príncipe (Prince's Tower, in the easternmost part, served as a lighthouse and displays three coats of arms: Austrias, Sotomaior, and the city's). Access is through four gates. The fortress was a crucial strategic point in the defense of the town and the estuary. After the arrival of the caravel Pinta in Baiona in 1493 with the news of the discovery of America, the Catholic Monarchs ordered the town to be established within the walled enclosure, granting it a Carta Puebla. Inside the walls is currently the Parador Nacional Conde de Gondomar, inaugurated in 1966. There is also a monument alluding to the Encounter between Two Worlds, from 1993.