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The Roman Cistern in Formia: the underground cistern that supplied Cicero’s villas
Beneath the medieval hamlet of Castellone, at a depth of over 10 meters, lies a structure that literally supports the houses above. The Cisternone Romano (Great Roman Cistern): dating to the 1st century BC, spans 1,200 square meters and has a capacity of 7,000 cubic meters of water. It supplied the whole area of ancient Formiae: private dwellings, fish-farming tanks (piscinae), and the villas of Marcus Tullius Cicero and Mamurra. For centuries, its exact location remained uncertain. In 1860, Pasquale Mattej collected accounts from those who had gone below ground to investigate, allowing for its precise identification.
Inside the cistern
The structure is arranged into four sections which are divided by 60 pillars, each 6.5 meters high, topped with pseudo-groin vaults. The massive masonry supports the entire medieval district overhead. Light filters sporadically between the pillars, creating effects that have led the structure to be called by some "underground basilica". The original entrance, located at the end of the central section and once used for drawing water, now serves as the visual centerpiece of the visit.
A legacy to rediscover
While often compared to the Basilica Cistern in Istanbul, a more historically accurate comparison is with the Piscina Mirabilis in Bacoli. The latter was built a century later when the Roman fleet moved from Formia to Misenum, likely using this large cistern as a blueprint.
