A network of underground tunnels that could accommodate up to 16.000 soldiers for over a year. Tunnels and hidden entrances that bore the names of English cities to orient oneself in 55 kilometers of labyrinths, shelters, hospitals, sheds and deposits: it is Great North Road, the underground fortress built in 1940 under almost 'a mile' of limestone that allowed the British to control access to the Mediterranean for the duration of World War II.
Initially based on the tunnels dug in the eighteenth and nineteenth centuries by the English engineers to connect the batteries that defended this British overseas territory - obtained following the Treaty of Utrecht (1713) - the fortress was expanded to the size of a gigantic shelter, able to protect from the attacks of the German Luftwaffe the entire British garrison that was placed to guard the fundamental 'narrow' that gave access to the Mediterranean: there where the mythology had posed the 'Pillars of Hercules'. The passages that led in and out of the tunnels carried the names of English cities and counties, such as Maida Vale, Peterborough, Doncaster, and Durham, to allow troops to easily navigate and reach the established locations.
The complex - that given undisputed security became the basis of the allied command from which General Dwight Eisenhower planned and directed the Operation Torch (the allied invasion of North Africa in 1942) - it housed everything necessary to be self-sufficient and isolated from the outside: large power plants (which supplied 1.200 kW of energy), a hospital, a desalination plant water, a bakery, a frozen food warehouse, ammunition depots and remittances for repairing damaged vehicles.
Despite repeated attempts to sabotage at the hands of Spanish agents hired by the Germans and those attempted by the Xª MAS incursors - who settled for a long time in a villa on Spanish soil only 3 kilometers from the border - Gilbiterra remained under the control of the allies for the duration of the war.
The Operation Felix, designed by the Germans 1940 to invade Gilbelterra and to which the 'commando' Brandenburg should take part, several battalions of the Großdeutschland and Gebirgs Division with the intended use of well 150 demolition mini-tank Goliath, was finally canceled in the 1941.
The tunnel continued to be used during the Cold War. Until 1968 had been guarded by a unit of specialists and designated as a possible underground shelter in the event of a nuclear explosion. He later abandoned himself to become a museum.