- Population: about 5,500 inhabitants
- Zip/postal codes: 07031
- Dialing Area Code: +39 079
- Patron Saint: Sant'Antonio Abate, celebrated on 17 January
- Frazioni & Localities: Lu Bagnu, Multeddu, San Giovanni, Terre Bianche
The castle was never conquered in the course of the centuries. In the early 16th century the name was changed into Castel Aragonese and finally, when Sardinia passed under the Savoy, to Castelsardo. In the 19th century there was a decline of the economy and a large part of the population emigrated. In more recent times however, tourism is giving a growing impulse to the territory and the economy.
- The Lunissanti, during the Holy Week, a pilgrimage held since the 16th century, organized by the Confraternita di Santa Croce to the abbey of Tergu.
What to see
- The domus de janas called Elephant's Rock.
- The pre-nuragic wall on Mount Ossoni, near Multeddu and the nuraghe Paddaju, as well as others in the territory.
- The Fortezza Bellavista, the seat of the Mediterranean Museum.
- The Cathedral of Sant'Antonio Abate, with an altarpiece by the anonymous maestro di Castelsardo and a majolica dome, with underground crypt.
- The church of Santa Maria with a wooden statue of a black Christ.