The castle, called Orgoglioso in the earliest sources, rises on an isolated hill around three km. from Silius. Completed around the middle of the thirteenth century, when southern Sardinia was largely dominated by the most powerful Pisan cemeteries, it was later bought by the Comune of Pisa which transformed it into a military base . It was besieged and destroyed around the middle of the fourteenth century by Mariano IV of Arborea, when the Catalans had already conquered the territory of Cagliari and assigned this area of the island to new feudal lords. A series of excavations has brought to light the whole of the structure, consisting of a trapezoidal outer wall closed on one of its short side with a semi-circular section, and on its other with a tower flanking the gate. A series of rooms opens onto the central courtyard, distributed on several storeys and linked by short flights of stairs. The earliest phase has large rooms, with arched windows and niches framed by neat stone edging. In the later phase these rooms were subdivided by walls of pebbles and earth. To this phase is attributed a small, well-preserved oven, the only medieval example of this type of structure. The most recent excavations have reached rooms below the level of the courtyard, situated in the service area, and perhaps destined for the conservation of foodstuffs and granaries. This is suggested by the find of a millstone in one of the rooms above, which also contained the oven, and may have been linked to the lower room by a trap door. On the exterior, only partially explored, a short stretch of the entrance road has been revealed, with, on the slope below, a manger for horses obliterated by a refuse dump.