A system of underground cuniculi was identified during rescue excavation on a building site. Of the first tract between two open air wells, 7.67 m apart, only a minimal part of the vault was preserved. Amongst the few archaeological material recovered during excavation were a number of tiles and bricks, coarse cooking ware, refined plain buff ware and amphorae of late Republican date. It was clear that the _cuniculus_ followed the slope of the valley, from north to south, in the bottom of which the Fosso di Tor Bella Monaca flowed. Therefore, a cut was made into the bed rock of Tufa di Villa Senni, typical of the volcanic area of the Alban Hills. This intervention revealed a section of the gallery that was almost free of debris and earth. The _cuniculus_ had a typical ogival section, 1.70 m high with a _maximum_ width at the vault impost of 0.60 m, the space necessary to allow a man to work inside it, and a _minimum_ width at the bottom of 0.38-40 m. A little further on the structure narrowed, the height became 1.14 m and the width at the vault impost was only 0.40 m. At a distance of 36 m from the second well was a third, 1.50 m long and 0.88/0.49 m wide. At the north-eastern end it was joined, as well as by the above mentioned _cuniculus_, by a second gallery descending from the east and 0.65 m wide. Both cuniculi were completely blocked. On the long sides of the well, as in the previous one, the characteristic foot-holds were visible. The fill that was excavated produced several tile fragments and an amphora stopper as well as a truncated pyramid shaped tufello, typical of _opus reticulatum_, with traces of mortar on the contact surfaces. On the south-west side of the same well was the entrance to a third _cuniculus_ which channelled the waters from the other two downhill. In this case the vault was almost flat; the gallery was 1.80 m high, it was 0.65 m wide at the impost and 0.40 m wide at the bottom. In conclusion, given the rural context this hydraulic system was used to collect and channel surface water towards a ditch downhill; the latter was identified during the investigation of an area south-east of this one. The first two wells found, which opened at the bottom of a ditch like a sort of swallow hole, channelled the waters into the subterranean gallery. The third, at the meeting of the two cuniculi, provided access for necessary maintenance.