Pedres Castle
The Castle of Pedres, or rather its ruins, is located on a hill 89 meters high, not far from Olbia. Two rows of walls are relatively well preserved. The first wall, very large and square in shape, runs down the slope; the second wall encloses an area of 1,000 square meters. Most likely, it protected the residential quarters. The castle itself was built from granite blocks, some of which were taken from nearby megalithic structures-nuraghes (towers) and dolmens (megalithic tombs). Most scholars believe the castle was constructed between 1296 and 1322, during the period of Pisan-Aragonese rule on the island, and served military purposes. The castle was finally abandoned in the mid-15th century, along with the town’s decline and the population leaving the city.
Roman aqueduct
The Romans took Sardinia in 238 BC, after which Olbia became an important strategic point and seaport connecting the mainland and the island. In Olbia, they even built Sardinia's only aqueduct, stretching 7 kilometers, which collected water from springs on Mount Cabu Abbas and pumped it into the city center. In the Sa Rugittu area, the aqueduct widens-here a large stone reservoir was installed with six openings for air circulation and containers for drawing water. Remains of the aqueduct have survived to this day- it was restored in 1989-1990. As a result, the underground sections were uncovered, including the large reservoir.