Near Piazza del Plebiscito and a little way up Via Gennaro Serra, a tiny vicoletto provides another route into the heart of the underground. You begin in a former veterinary clinic before descending tuff stone steps down into the Bourbon Tunnel.

The year 1848 was tough for any European monarch; riots and revolution were the order of the day in many cities. This made King Ferdinand more than thoughtful as he sat in his new palace in Naples. What he needed most of all was a possible escape route. So in 1853 he commissioned architect Enrico Alvino to construct a tunnel from the royal palace to a spot near the barracks at Piazza Vittorio. Officially this was to be a double tunnel, the King’s and Queen’s tunnels running parallel, full of stores and with an elegant interior. But in reality, the workers not only had to dig through the tuff rock to create a new passageway, but they also had to cross the existing water system that Cesare Carmignano had devised in the 17th century. This part, at least, was accomplished by bridging cisterns and carving out new spaces where once only the pozzari had ventured with their lanterns. Work stopped after two years and soon Ferdinand and his building projects would be overtaken by political changes that swept across Europe.

As with many other underground spaces, the tunnel was used as an air-raid shelter during the Second World War; cisterns were filled with earth to raise them to usable levels, low voltage electricity supplies were installed along with toilets and showers. One can only imagine how difficult it was to endure months of bombing in these dank spaces. Down here, as you pass along the corridors and through echoing cisterns, you can see heart-rending messages on the walls – Noi vivi or “We are alive” – and view the remains of beds and children’s toys.

Towards the end of the tour comes a real surprise, the ghostly chassis and frames of cars, vans, and bicycles along the passageways. The tunnel was used as storage for vehicles confiscated from Neapolitans who engaged in contraband trade, chiefly that of tobacco. Just before emerging, blinking into the light of day at Via Morelli (grateful there are no stairs to climb back up) you see the broken fragments of an enormous statue that once stood in Piazza Santa Maria degli Angeli – a monument to Aurelio Padovani, the fascist leader of Campania in the 1920s.

Padovani died, along with eight other people, when he stepped out onto a balcony in Via Generale Orsini to greet enthusiastic crowds on his name’s-day and the railing gave way. Conspiracy theories abound as to whether Mussolini, jealous of Padovani’s popularity and power in the south, had orchestrated his demise. Il Duce commissioned his statue, whether in a fit of regret or cynicism, and the monument remained in the little square throughout the war. How the pieces came to be found under layers of trash and rubble in the Bourbon tunnel is yet another mystery.

It took five years for the teams of speleologists and various volunteers to clear out the accumulated lumber and refuse, but now the tunnel offers a great glimpse into the history of Naples at three key points in its history.

Visit the Bourbon Tunnel