Galleria Borbonica (Bourbon Tunnel), Naples (must see)

The Bourbon Tunnel was conceived in 1853 during the reign of King Ferdinand II of Bourbon, and was originally intended as a secret military and escape route linking the Royal Palace with strategic points farther inland, such as military barracks on Morelli Street. The Bourbon monarchy of the time was wary of uprisings, and this underground corridor was meant to offer a rapid and discreet way for troops — and potentially the royal family — to move unseen or flee if the city erupted in revolt. Unfortunately, King Ferdinand II died and the tunnel was left unfinished. Despite the sudden interruption of construction works, the tunnel had already been connected to the 17th-century aqueduct system.

After the king's death, the underground space went unused until World War II. During World War II, it became a vital bomb shelter and refuge for thousands of residents, seeking safety from aerial bombardments, with makeshift facilities added to accommodate them. After the war, it was used for storage — at times housing impounded vehicles.

After being rediscovered and cleared in the early 21st century, the Bourbon Tunnel emerged as a popular attraction. Nowadays, guided tours take you through sections of the tunnel where you can see remnants of its varied uses: ancient water systems and aqueduct connections, wartime artefacts such as vintage cars and motorcycles left behind, and the tunnel’s narrow corridors. Some tours delve deeper into adjoining cisterns or offer more adventurous explorations of less visited branches.