In order to secure their coastal region – especially the Strait of Gibraltar - the Spanish government signed a purchase agreement on June 23, 1927 with the English company Vickers Limited for ten coastal defence guns: 381/45 mm Model 1926 Vickers guns to be exact. The Vickers 381/45 calibre guns have a good firing range of 38,276 yards. At its narrowest point the Strait of Gibraltar is 15,310 yards wide. A 45-calibre gun is able to fire two shells weighing up to 1,951 pounds per minute at a muzzle velocity of 833 yards per second. The Vickers 381/45 were each mounted on a turret that was mainly underground. The turret contained numerous rooms and passageways, e.g. machine rooms, lift systems, magazines and storage areas. Between 15 and 20 people were needed to operate the gun.
When one of the guns was being installed in the Paloma Alta Battery not far from the Strait of Gibraltar, the geographical location made a couple of special features necessary. In order to hide the large base of the gun, it was embedded in a man-made hill covered in artificial blocks of stone.
The Paloma Alta Battery is located roughly 1 mile from the Atlantic Coast in the foothills of the Baetic Mountains. It is a rugged area rich in forests. The man-made boulders are in an area that is approximately 1,196 square yards in size. The boulders, which lie next to each other and on top of each other, look like a large collection of huge glacial erratics. They are made out of cement-bound mortar and were moulded on a metal lattice frame. They were made with such care and precision that there are only a few places where you can see a mark left by a trowel or a place where a piece of the metal lattice peeks out from beneath the age-worn mortar. After decades of lying in the middle of the woods in rugged terrain the elements have taken their toll on the surface of the man-made boulders. They are also now covered in lichens. Shrubs and trees grow in the cracks. In fact, today, even after careful inspection, the blocks of stone can hardly be distinguished from volcanic rock such as andesite and dacite – a type of rock that is not indigenous to the area. It would take a mineralogical analysis at a lab to confirm that this is indeed not natural rock at all.
