Underground channels dating to as early as the sixth century BC, frequently found cut into the tuff bedrock in South Etruria to carry runoff water, in both urban and rural contexts and, in some circumstances, to provide a water supply. The most dense zone of rural cunicoli in Etruria was in the territory of Veii. The most elaborate and visible single example is the Ponto Sodo, originally some 100 meters in length. Other systems in the same area have measured almost a kilometer in length. Their construction may be connected to the intensive cultivation of the landscape, particularly of tree crops such as the olive.
Historical Dictionary of the Etruscans. Simon K. F. Stoddart.