The Roman roads in Tharros form a triangular square in the centre of the city, onto which a building known as the castellum acquae looks down (figs. 1-2)

Fig. 1 - Location of the castellum aquae (from Google Earth. Review C. Tronchetti)

Fig. 2 - The castellum aquae (photo by Unicity S.p.A.)

This was a building used to preserve and distribute water to the Tharros citizens, which was supplied by an aqueduct, little of which remains, and only outside the city.

The structure is rectangular with no openings. It had an external façade alternating rows of bricks with sandstone blocks; internally, the walls are brick, covered by a thick layer of hydraulic lime and crushed bricks, a limestone plaster with added terracotta fragments that guaranteed it was impermeable. Water flowed out of this large cistern from three holes in the top part of the southern wall, into a decantation tub, and then flowed into the semi-circular public fountain on the southern front of the building that looks onto the square (figs. 3-4).

Fig. 3 - The front of the castellum aquae (photo by Unicity S.p.A.)

Fig. 4 - The castellum aquae with the decantation tub and the base of the public fountain (photo by Unicity S.p.A.)

Based on the building technique used, the castellum acquae can be dated between the 2nd and 3rd century A.D.

The building lost its function in the Late ancient era; an opening was made in the western wall and it was used for a different purpose, which is not clear.