The castle was built in the 12th century by the Doria family of Genoa atop the promontory of Castelsardo standing high above the bay. The walls and the entire structure are well preserved, as the distance from the salt water prevented phenomena of erosion.
The castle houses the Museum of Mediterranean Weaving, one of the most important museums of Sardinia, dedicated to the local tradition of weaving baskets and other implements of everyday life.
From the terraces along the wall, you can enjoy the sweeping view that encompasses most of the northern coastline and the island of Asinara. On clear days you can even see southern Corsica.
During the Doria dominion, the castle was the stronghold of their extensive landholdings.
Up to the mid-19th century, a number of watchtowers still existed, but they eventually crumbled and were not rebuilt. In some segments you can still walk along the guard pathway, and the bastions are still visible: to the east Bellavista, to the north Manganelo, and to the southeast Loggetta and Sperone, added in the 16th century by the Aragonese. After the fall of the Doria family, in fact, the Spanish court sent its viceroy Vivas to ascertain the conditions of the stronghold and to prepare a report detailing the works necessary to restore the fortification.