The Roman Tanks are located under Piazza del Popolo, corresponding to the public area of the Roman period (Forum), which now overlooked by the main public and religious buildings of Todi. Represent the most important monument of hydraulic engineering of the city designed in Roman times, visited by a suggestive underground. The monument consists of two twin tanks: the east, stretching along the Palazzo del Capitano and Palazzo dei Priori; the second, parallel, under the initial stretch of Via del Monte. Similar in structure and size, the tanks have a rectangular plan divided internally by twelve adjoining rooms. The work was used to supply water to the hill, and helps to enrich the heritage of underground city, consisting of a network of wells, tunnels and tanks of all time. Coeval to the forensic square, underwent a first restoration already in the second century AD.