The rural building known as Sas Presones in Bonorva is a short distance from the village of Rebeccu and the necropolis of artificial grottoes of San Andrea Priu, in a very important area for the Roman road system in Sardinia. It is assumed that the main road to Karalibus Turrem (from Cagliari to Portotorres), branched off towards Olbia (fig. 1) right here on the Campeda high plain. The several findings of the columns (milestones) placed b the Romans on the most important roads to show distance in miles in this area are useful for locating the fork in the road.

Fig. 1 - In yellow, the road for Olbia; SP = Sas Presones, CA = Cantaru Addes, SL = Su Lumarzu, TN = nuraghe Tresnuraghes (from IALONGO ET ALII 2007, p. 208, fig. 1).

Known already in the nineteenth century, the building of Sas Presones was a part of a thermal bath complex from the Late Antique Age, relating to a public building, praetorium, that service the road system leading to Olbia.

The recent restoration work of Sas Presones allowed a careful study of the remaining rooms and the overall layout of the original building, that had at least eight rooms (fig. 2).

Fig. 2 - The building of Sas Presones in Rebeccu after restoration (by MASTINO, RUGGERI 2009, p. 556, fig. 2).

Room no. 1, which is rectangular (5.70 x 3.60 metres), was interpreted as a frigidarium, one of the main areas of thermal baths in the Roman era where it was possible to bath in cold water. Room no. 5 (4.50 x 3.00 metres) could instead have been the apodyterium, i.e. a non heated area that was used as a changing room; on the west side there is a terrace, close to room 8, with a tub for baths. The hot rooms are in the lower part: in no. 2 (5.40 x 3.60 metres) there is the the tepidarium, a passage between the hot rooms and the frigidarium, which was sometimes also used as the room for unctions; to the sides of it, there are the sudatoria (Turkish baths), two small rooms 6 and 3, heated like the nearby room 4, that may have been the actual calidarium, the heated room for hot water and steam baths, with the praefurnium next to it on the north side (fig. 3).

Fig. 3 - The rooms that makes up the thermal bath complex of Sas Presones (by IALONGO ET ALII 2007, p. 210, fig. 3).

Recent archaeological surveys brought to light the original floor in the central tepidarium (room 2) made with rectangular basalt rock slabs, suspended on 24 trachyte pillars 60 cm high, that are actually fragments of milestones blocks carrying traces of inscriptions (fig. 4).

The milestones probably come from the fork in the road, after Campeda, that leads to Olbia and Turris. It has been hypothesised that after being replaced, they were stacked in a collection centre and then reused as building material in the thermal baths.

The milestones show the titles of emperors from the 3rd to the 4th century and show the date that must be that of the construction of the thermal baths.

Fig. 4 - The milestones that support the floor in room 2 (by MASTINO, RUGGERI 2009, p. 562, fig. 8).

The building of Sas Presones may therefore be dated to the end of the 4th century A.D., as the road milestones reused in its structures cover a period of time from the age of Galerius to Constantine or Julian. The thermal baths building of Sas Presones underwent changes in both the Medieval era and Modern times, that determined a progressive rising of the floor.