Castelsardo small craft and yacht harbour is protected from the NW by a mole extending 450 m NE from the coast which incorporates Isolotto di Frigiano (Frigianu) at its mid-point. Molo Foraneo, the part of the mole NE of Isolotto di Frigiano, protects the harbour entrance which lies between a short rubble spur extending ESE from Isolotto di Frigiano and a short rubble breakwater extending NW from a rocky point on the coast; Torre Frigiano stands on the point.