The hidden underground world beneath an Italian city

In the early 1850s, Ferdinand II of Bourbon, King of the Two Sicilies, was a monarch with security issues. Besieged by revolutions, the shaky sovereign came up with a plan as grandiose as his title: to build an escape hatch connecting his royal palace in Naples to the military barracks near the sea.

A sound plan, but an assassination attempt in 1856 – by means of a bayonet to the guts – meant our nervous noble died a few years later, from complications brought on by infection. And the sneaky royal route? As useless to him as olive oil on a fire.

A view of the river in the Bourbon tunnels, an underground way used by the military during World War II.Credit: Getty Images

Today, the Bourbon tunnels (Galleria Borbonica) are a tourist attraction for those looking to explore the “other” Naples, and are the highlight of a shore excursion during our seven-day Mediterranean cruise aboard Sun Princess.

“The underground tunnels were designed to be wide enough for troops and horses,” says our guide Lucia Nillo, catching me side-eyeing the narrow walls of the entrance steps.

Down the rabbit hole we go, plunging 40 metres to the fourth century BC, when the Greeks first tunnelled through the volcanic rock to build an intricate network of water reservoirs and cisterns.

“Later, the Romans expanded it to create their aqueduct system, which was extended even further when King Ferdinand II built his escape tunnel,” says Nillo.

The remains of vintage cars and motorcycles in the tunnels.Credit: Getty Images

To my wandering mind, the dimly lit passages are a cross between the crypts beneath Game of Thrones’ King’s Landing and the hidden bunkers from The Walking Dead. Tally-marks and directional arrows etched into the walls add to the intrigue.

Behind me, the stone steps twist into a Penrose impossible staircase, each flight appearing to lead both up and down. Ahead, the aqua-blue waters of a shallow cistern casts an other-worldly glow across the chamber.

As we skirt the still waters, Nillo shares the legend of the Munaciello, a monk-like spirit that is said to inhabit the sewer, capable of malevolent mischief or good deeds. “If something goes missing in our homes, Neapolitans will always blame the Little Monk,” says Nillo, crossing herself and looking around.

Signs of the past in the tunnels.Credit: Adobe

Entering another dark chamber, Nillo points out a series of vertical notches carved into the high walls, where, during the 18th century the “men of the wells” would descend from the mansions above to clean the aqueducts. “Many would fall and die,” she says. “And if that didn’t get them, cholera would.”

It was the 1884 cholera outbreak that led to the tunnels being closed, and as the city built new systems, the ancient underground became a dumping ground.

Abandoned for decades, the tunnels found a new purpose during World War II, serving as a semi-permanent refuge for thousands of Neapolitans whose homes were destroyed by bombs.

“Conditions were dreadful,” says Nillo, gesturing to a row of just seven toilet cubicles – cement partitions without doors. A mental picture of the overcrowded bomb shelter and makeshift hospital makes the hairs on my neck stand up. Earlier, Nillo had activated the air-raid siren, its piercing wail chilling me to the bone.

By 1950, the tunnels were sealed off until their accidental rediscovery in 2005.Credit: Adobe

Around the next bend, there’s another plot twist – a vintage-car graveyard comprising Vespas, Fiats, luxury cars and military jeeps. I’m no car enthusiast, but eavesdropping on others, I learn that this may well be the most remarkable motor museum of all time. But rather than showroom condition, the abandoned vehicles are all covered in a fine dust like they’ve been unearthed from an archaeological dig. Some even have small lamps tucked into their empty headlights, glowing like eyes amid the gloom.

“When the war ended and people went back to their lives, the tunnels were used as an impound site,” says Nillo. “There simply wasn’t room on the streets for all the damaged and derelict vehicles.”

By 1950, the tunnels were once again abandoned and sealed off until their accidental rediscovery in 2005.

“We can’t hide it,” says Nillo. “There’s been a lot of sadness down here but if we remember our past, we can try to create a better future.”

The tunnels are a graveyard for military vehicles in the basements of Naples.Credit: Getty Images

THE DETAILS

FLY
Qatar Airways operates multiple daily flights out of Australia, connecting through Doha to Barcelona and other European cities. See qatarairways.com

CRUISE
A cabana mini-suite on a seven-night Mediterranean voyage, departing Barcelona on June 7, 2025, visiting France and Italy and finishing in Naples, costs from $3789 a guest on a Princess Premier package. It includes Wi-Fi (up to four devices a guest), premier beverage package, two speciality dining meals and unlimited fitness classes. See princess.com/sun-princess

The writer was a guest of Princess Cruises.