The granite hill of Castro (the toponym is the one recorded in the IGM cartography) is located in the central portion of the Monteacuto valley. The relief, even if it does not exceed 200 m, has an elliptical tabular summit (m 250 x 90) with marked and elongated slopes towards the course of the Mannu di Ozieri River. The watercourse is no longer detectable in its original morphology since it has been incorporated into the artificial Coghinas basin that occupies the entire northern portion of the Monteacuto Valley.
The “Itinerarium Antonimi” (3rd century AD) brings back, along the road “to Tibulas Caralis”, the center of Luguidone at an equal distance (about XXV miles) from Gemellas (Perugas) and Hafa (Mores). Anonimo Ravennate's 6th century 'Cosmographia', in the middle of the Byzantine era, mentions the 'castra Felicia'. Scholars agree on the location of these centers with the ruins located in N/O di Oschiri, recognizing the settlement, in addition to a military function, a key role in the road network of northern Sardinia. In fact, the road is actually part of the one that guaranteed the connection with the center of the island. After crossing the Campeda plateau, it was divided into two arteries: one towards Turris, the other towards Olbia. A second route allowed the direct connection between the 'Luguidonis c (astra) 'and the 'Portus Luguidonis' located near Santa Lucia di Siniscola. A firm propensity for continuous attendance at the top of the hill is also evident in the location, in this same place, of the medieval diocese of Castra. The church of Santa Maria (12th century) is located about 1 km from the Roman remains.
Archaeological research, concentrated in the eastern portion of the hill, has made it possible to highlight a portion of the wall in frame work (“opus africanum”) attributed, in its planting phase, to the Julio-Claudian age. The wall circuit, documented in its entirety thanks to area photography, has a trapezoidal profile suitable for closing the entire top of the hill. Some wall curtains and several artificial terraces have been recognized along the S side of the relief. Two excavation tests along the E portion of the wall have verified that the structure was not built against the ground but on a pre-existing structure in lithic material, linked with mud mortar, placed directly on the rock bench. In the easternmost excavation essay, a large rectangular block placed vertically was highlighted. This element has been interpreted as a jamb of an access door to the city open to N. Inside the wall, always in the eastern portion, close to the entrance, a thermal building has been found. The building has a length of 22.20 m and a width between 7.4 m and 13.3 m. At the maximum width, there is the “frigidarium” equipped with a tank that, in its last phase of use, was covered with bricks. In succession, there are the hottest environments: the 'tepidarium' and the 'calidarium'. The latter shows two tanks. The entire plant was built during the first century AD, but the signs of subsequent transformations are evident, witnessed by the use of ribbed embryces that bear the stamp “Valeri”, originally attributed to the second century AD. Not far from the thermal complex, some environments characterized by a floor and wall covering in signine work have been investigated. These spaces have been interpreted as warehouses for wheat; however, their destination as warehouses for water is not excluded. In the N, outside the walls, there is a necropolis. The burials, in the urn and cappuccina, have not been investigated.
From an interpretive point of view, it is evident that Luguidune-Castra assumed a proto-urban role for the territory for a very long time: it is almost a city equipped with public spaces, defensive structures and areas for civilians to be located on the southern slopes of the hill. The epigraphic sources, especially funerary epitaphs recovered in the Iscia Cunzada region, less than 2 km W from the Castro hill, attest to the presence of the “III Cohors Aquitanorum” starting from the Julio-Caudian age. The department consisting of 500 personnel, probably quartered on the hill inside a fortified wooden structure, was probably accompanied during the Neronian age by a “Cohors Ligurium equitata”. In the same area, the work of the 'Cohors Sardorum' seems to have been attested during the Flavian Age, but there are not sufficient elements to define if there was a change between the different departments. The stable presence of the military in this area starting from the first century AD was motivated by the need to protect the roads from the incursions of the Balars, a population that was not completely Romanized, settled in the Limbara massif.

History of excavations
The presence of road sections, together with the remains of walls on the top of the hill, is documented in the 16th century descriptions (Giovanni Francesco Fara) and in those of the 18th century pertaining to the duchy of Monteacuto (fiefdoms of the Spanish family of Oliva). The Roman site has been archaeologically investigated starting in 1987.

Bibliography
A. Mastino-P.G. Spanu-R. Zucca, “The territory of Oschiri from the Roman period to the Byzantine Age”, in Oschiri, Castro and the Eastern Logudoro, Sassari, Carlo Delfino, 2004, pp. 77-99.
L. Pani Ermini, entry “Castra”, in Encyclopedia of Ancient Classical and Oriental Art. Second supplement 1971-1994, II, Rome, 1994, pp. 41-42.

How to get
From Sassari, along the road to Olbia (SS 597), after the high-speed section has been inserted, the site is visible on the road to Olbia at the turn for the church of Our Lady of Castro. Once you reach the church, continue, for more than a km, along the same road to the hill of San Simeone.