A labyrinth of Greek and Roman-era tunnels running beneath the streets of the Centro Storico, accessible through an entrance on Piazza San Gaetano. The tunnels were originally quarried for tufa — the soft volcanic stone used to build the city above — and later converted into cisterns for the Roman aqueduct. The network extends for about 80 km beneath the old city.
Tours descend 40 metres below street level through passages carved 2,400 years ago. The route includes ancient cisterns, wartime air-raid shelters, and a section where visitors must squeeze through narrow passages with candles in hand. Book ahead in high season; the 90-minute guided tour is the only way in. One of the genuinely extraordinary things in Naples.