The History of Naples Underground
The story of the Naples Underground is the story of the city itself, told from below: quarried by Greeks, engineered by Romans, forgotten, and then sheltering a population through the bombing of the Second World War.
Greek beginnings
When Greek settlers founded Neapolis, they cut building stone from the soft volcanic tuff beneath their new city. The quarries they left behind became the first great voids in the rock — hollow chambers that later generations would connect, extend and put to use. The same easily worked stone that raised the buildings above created the network below.
The Roman aqueduct
The Romans turned those cavities into infrastructure. They built an aqueduct and a web of cisterns that carried and stored the city's water, tunnelling channels through the tuff and lining them so they would hold. For centuries a caste of well-keepers maintained the system, lowering themselves through narrow shafts to clear and repair the conduits that fed fountains and private homes far above.
Water, plague and abandonment
The underground supplied Naples with water into the modern era. After a cholera epidemic in the 1880s, the old well-and-cistern system was blamed for spreading disease and a new pressurised aqueduct replaced it. The ancient network was sealed and, for decades, largely forgotten — remembered mainly as the space below the floorboards where debris was dumped.
Shelter under fire
The Second World War gave the tunnels a second life. As Allied bombing raids struck the city, Neapolitans descended into the old cisterns and passages by the thousand, turning the cool, deep galleries into air-raid shelters. Families lived below for long stretches; the graffiti, furniture and everyday objects left behind are still part of what visitors see today.
Rediscovery and the Roman theatre
In the second half of the twentieth century the underground was cleared, mapped and gradually opened to visitors. One of its most surprising discoveries sits at the boundary between the buried city and the living one: a Roman theatre, where the emperor Nero is said to have performed, preserved beneath later apartments and entered through an ordinary-looking building at street level.
The well-keepers and their legends
For as long as the system carried water, a guild of well-keepers — the pozzari — kept it working. They squeezed down the narrow shafts to clear blockages, patch the render and draw water up to the houses above. Living half their lives in the dark, they gathered a reputation for appearing unexpectedly in cellars and courtyards, and folklore turned them into the Munaciello, the little monk who might leave a coin or play a trick. The legend is a reminder that this network was never just plumbing; it was a lived-in second city, woven into the imagination of the streets above.
Scale and rediscovery
The full extent of the tunnelling runs to many kilometres of hand-cut passage beneath the historic centre, only a fraction of which is open to visitors. Much of it was mapped and cleared only in recent decades, as volunteers and speleologists hauled out the rubble of a century of dumping and reconnected chambers that had been sealed since the 1880s. What you tour today is a curated, safe route through a far larger warren — enough to make the point, without pretending to show the whole.
Not the catacombs
It is worth clearing up a common mix-up. The Naples Underground is an aqueduct-and-shelter network; it is not the Catacombs of San Gennaro, which are a separate early-Christian burial site on the hill of Capodimonte. Different place, different story, different ticket.