According to a royal warrant issued by king Alfonso XI the wall was built around 1337. Notwithstanding evidence confirms that the castle did already exist in the 10th century. The fortress represents the visible consequence of king Alfonso XI's disagreements with the king of Portugal.

In 1497, the Catholic Monarchs ordered the population in Baiona to live inside de walls. Nevertheless, the inhabitants were not happy with the royal decision and only observed it for a few years. After that the fortress became residence for military governors commanding the area -for instance, the Count of Gondomar.

Nowadays the area is a State Hotel where the three surveillance towers still stand. The Tower of the Clock is found near the entrance. Inside this tower there was a hidden warning bell which served as an alarm in case of enemy attacks. The Tower of the Tenaille rises to the East: its duty was to defend the port with artillery. In the West the Tower of the Prince stands over the bay. This is probably the oldest tower and it used to serve as lighthouse for vessels. It shows three coats of arms (the Austrias's, the Sotomaior's and the one of Baiona). The tower was named after the Portuguese prince Afonso Enriques, imprisoned inside the tower in 1137.

The Fortress can be visited all through the year (admission: 100 pesetas). Amazing sunsets over the ria and the Cíes islands can be admired from the walls. Not to miss the coastline along which Baiona stretches.