An aura of mystery surrounds the ruins of a fortress near Santa Maria Coghinas, in the historical region of Anglona. Perching on the granite mountain known as monti di lu Casteddu (or Mount Urtigiu), along the Mount Ruju chain, Casteldoria (or Castello dei Doria) overlooks a fertile valley fed by the "healing" waters of the River Coghinas and Lake Casteldoria, where the Romans built an important bath complex. The castle was built around the 12th century by the Genoese Doria family, and passed from the Genoese dominion to the Aragonese, then to the Arborea Giudicato and lastly to the Malaspina family.

Only a few ruins remain of the fortress: parts of the walls, the remains of a chapel and a large cistern that was probably used to collect and store water. The famous tower, on the other hand, is well-preserved, and is an important part of the castle, built in large, rectangular granite blocks set in mortar.