Lurking about 100 feet below the streets of Naples is a cavernous tunnel filled with rusting vintage cars and wartime relics, that was originally built to be as a secret escape route for the royal family in 1853.

The tunnel was commissioned by King Ferdinand II of Bourbon (the same French dynastic house that lent its name to New Orleans’ famous Bourbon Street), who reigned over Sicily and Naples during a tumultuous period marked by riots and uprisings. It was meant to be a passageway from the Royal Palace to the military barracks, in case the royal family needed to flee the revolting populace.

The tunnel was dug out of the volcanic rock below the city, connected to the existing, early-17th-century Carmignano aqueduct system. However, the king died before the tunnel was completed, and it was left unfinished and largely forgotten until World War II.

During the war the subterranean corridors and neighboring cisterns were used as air raid shelters, housing up to 10,000 Neapolitans. On a historic tour of the tunnels you can see artifacts left by the people who sheltered here, including children’s toys, gas masks, and personal items like hair brushes. You can even see the remains of toilet blocks and beds.

After the war the Bourbon Tunnel (Il Tunnel Borbonico) became a dumping ground for wartime rubble and unwanted debris, storing everything from fascist statues to impounded cars from the end of the war until the 1970s, when the tunnel was forgotten again.

The tunnel was restored in the 2000s and now the vintage cars and wartime rubble scattered throughout the tunnel are on display in the eerie space, dubbed the Bourbon Gallery (Galleria Borbonica). It’s not far from the Naples Underground, another entrance to see the maze of underground tunnels hidden beneath the ancient city. Tours of the site are given, including expeditions into the darker corridors of the historic tunnel.