A report from the Carabinieri led to the investigation of ancient hydraulic structures in the area of Pian del Terminaccio (Vt), in the territory of the Etruscan town of Norchia which prospered in the Hellenistic period. The investigation looked at an area of agricultural land adjacent to sites where the presence of other Etruscan-Roman hydraulic structures had been noted, mainly comprising tufa cut cuniculi for drainage. The structure at Pian del Terminaccio was originally a drainage duct – of the widely used monumental type – which was later widened and altered enough to be defined as a “cuniculus cistern”. To judge by what has been published, this type of structure would seem to be rarely attested in South Etruria. However, it is more likely that the lacuna in the published record does not coincide with the archaeology but is only due to a problem of methodology, that was linked until recently, to the underestimation of the presence of structures of this type.