This tiny territory on Spain’s southern tip has been the subject of fierce diplomatic wrangling for years. Spain claims sovereignty, but it’s been ruled by Britain since 1713. Dominating the territory is the famous limestone Rock of Gibraltar promontory, which was once considered one of the two Pillars of Hercules and later become a prized military asset, especially during World War Two.

Today, work inside the Rock is revealing thousands of years of history, including information on how it was repurposed as a military headquarters during the war. There are many miles of tunnels inside, more than twice the amount of roads on the outside. Once considered an urban myth, evidence of a top-secret plan to hide spies inside a cave in the Rock has been also discovered. Now, up to 30 people a year can visit this secret location.

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Source:http://www.bbc.com/travel/story/20200813-gibraltars-infamous-stay-behind-cave?ocid=twtvl