Piscina Mirabilis

An archaeological pièce de résistance, the Piscina Mirabilis lies tucked away in a Bacoli backstreet. To access it, contact custodian Signora Filomena at No 9, who has the key to what is the world’s largest Roman cistern. Bathed in an eerie light and featuring 48 soaring pillars and a barrel-vaulted ceiling, it’s more ‘subterranean cathedral’ than ‘giant water tank’. The cistern was an Augustan-era creation, its 12,600 cu metre water supply serving the military fleet at nearby Miseno. Fresh water flowed into the cistern from the Serino river aqueduct, which was then raised up to the terrace with hydraulic engines, exiting through doors in the central nave. Engineers still marvel at its sophistication. Admission is free, but save face and tip the signora a euro.