These are the secret World War Two tunnels the British Army used to defend Gibraltar from a German invasion.
Christened the Great North Road, the mile-long bombproof tunnel runs right inside the Rock of Gibraltar.
It was built in 1940 so soldiers and equipment could remain safely underground while Luftwaffe planes bombarded the island.
Gibraltar was strategically extremely important during the Second World War, as it allowed the British to control access to the Mediterranean Sea.
After the war, the tunnels were kept intact by the Ministry of Defence just in case they should ever be needed again.
They are currently used for training troops in underground warfare.
Above ground, a gun battery still faces out towards the Spanish coast to guard against enemy warships trying to pass through.
The separate passages, or adits, leading off the main 60ft-wide highway are named after British districts and cities to allow soldiers to know where they are inside the rock.
The place names include Maida Vale, Peterborough, Doncaster, and Durham.
The tunnels house everything 16,000 soldiers needed to survive for 16 months – a telephone exchange, a generating station, a water desalination plant, a hospital ward, a bakery, a frozen food store, munitions stores and a station to repair damaged vehicles and passageways.
They were so well positioned and equipped that…
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