Underneath the streets of Naples in Italy, there is a network of tunnels that were built by Ferdinand II, who was a paranoid ruler of Bourbon back in the 1800s. He was planning to use this tunnel if there was a riot and this was his backup escape route.
The construction of this tunnel begun back in 1855 and as the technology back then was limited; the work progressed at a rather slow pace. The workers were making use of hand tools such as picks, hammers and wedges. The medium to light these tunnels were confined to candles and torches.
Four years after this project started, it was stopped as Ferdinand II died in 1859. Until World War II, the tunnels were closed. But during World War II, it served as a holding place for the military equipment and it also doubled up as a bomb shelter for the citizens.
Once the war was over, the tunnels were abandoned and things were left untouched until 2010, when they were opened again for restoration.
The tunnels are now used as the Galleria Borbonica and are open for visitors.