Great Siege Tunnels of World War II

The 52-km of Great Siege tunnels were hewn inside the rock by Merchant Marines in the 1700s to defend the island from siege and used to transfer cannons from one side of the island to the other. These tunnels were so successful that, in WWII, further excavation was done and an underground city of barracks, offices, caverns, and a fully-equipped hospital complex, including an operating theatre and X-ray unit, were constructed.