This is the largest cistern in the city, with a capacity of 5 million cubic metres of water and a depth of 15 metres, consisting of a series of bell-shaped cisterns and adjoining chambers connected by means of huge pillars.
To make it waterproof, the cistern was entirely plastered using cocciopesto, an ancient Roman technique which used fragments of finely crushed brick or tile and a fine mortar based on aerial lime. With the construction of the Apulian Aqueduct in the 1920s, it was closed and forgotten for decades.
The cistern was rediscovered in 1991 during the redevelopment of Piazza Vittorio Veneto. At the time of the discovery, being still full of water and not knowing its extent, rubber boats were used to explore.
Due to its size and structure, and its curved walls, the cistern is known as the “Cathedral of Water”.