The cave was accidentally discovered during World War II, when in 1942 the Royal Engineers were blasting inside the Rock of Gibraltar so as to create an alternate entrance to the lower chambers of St. Michael's Cave, which had been prepared as an emergency hospital.

[1] The cave's chambers include examples of almost all known cave formations, including a lake nearly 40 yards (37 m) long containing an estimated 45,000 imperial gallons (200,000 L) of crystal-clear water.

[1] After the war, the cave and every visitor was supervised by the United Kingdom's Ministry of Defence, specifically the Royal Engineers.

Within ten years, the guides were all civilians as the Gibraltar Tourist Board took over the cave's management from the military.

[2] Three-hour guided tours of the cave can be arranged, ending with viewing the underground lake.