Humans and apes were living peacefully till when one day, the latter decided to appropriate what the former left behind. – If human beings will not take this place, then we will do it! – Said by an ape.
A single limestone rock holds more abandoned fortresses than most countries.
Gibraltar is a British Overseas Territory occupying a narrow headland on Spain’s southern coast, dominated almost entirely by the Rock of Gibraltar itself — six square kilometres of limestone riddled, quite literally, with the remains of centuries of military construction. There is no single ruin to visit here and no single address to give: batteries, observation posts, gun emplacements and tunnel entrances from both world wars sit scattered across the Rock, some sealed, some fenced, some simply left open to whoever climbs high enough to find them. What follows draws entirely on military installations — bunkers, batteries, and observation posts from the First and Second World Wars — encountered across the Upper Rock.
Historical Context
A Headland Fought Over for Millennia
Human occupation of the Rock stretches back roughly 100,000 years, when early humans and Neanderthals fished its shoreline and sheltered in its limestone caves — Gibraltar’s caves have in fact yielded some of the most significant Neanderthal remains found anywhere in Europe. Phoenician and later Roman sailors passed through, but it was the Moorish commander Tarik ibn Ziyad, arriving in 711 AD, who established the first permanent settlement on the Rock, giving it the Arabic name from which “Gibraltar” derives. Its position commanding the entrance to the Mediterranean made it a prize fought over repeatedly by Spain, France and Britain in the centuries that followed, including the fourteen sieges collectively remembered as part of Gibraltar’s long military history, the longest and best documented of which is the Great Siege of Gibraltar (1779–1783).
Gibraltar at War, 1939–1945
Gibraltar’s strategic value peaked again during the Second World War. Most of the civilian population was evacuated for the duration, leaving around 4,000 residents to remain and support the garrison; the return of evacuees, according to accounts of the period, began in 1944 and continued in stages until 1951, years after the war’s end. Holding Gibraltar gave the Allies control of the western gateway to the Mediterranean and made it a critical link in supply lines to Malta and North Africa, as well as the base of the Royal Navy’s Force H. Germany did draw up plans to seize the Rock, codenamed Operation Felix, but the operation was abandoned when Francoist Spain refused to allow German forces passage through its territory; Gibraltar’s harbour was nonetheless attacked repeatedly by Italian frogmen operating covertly from bases across the bay in Algeciras.
Architecture and Space
An Underground City
The defining architectural feature of wartime Gibraltar is not visible from outside at all. The Rock contains an estimated 34 miles (55 kilometres) of tunnels, excavated in phases over nearly two centuries by British military engineers, nearly twice the length of Gibraltar’s entire road network above ground. The Second World War additions, carved out by Royal Engineers and Canadian tunnelling companies, were built to shelter the entire garrison — some 16,000 soldiers — along with a power station, hospital, water desalination plant, bakery, and ammunition stores, sufficient to withstand a siege of up to sixteen months. Higher up the Rock, along the ridge path leading toward O’Hara’s Battery, sits Douglas Cave, first occupied during the Great Siege and reoccupied in 1940. Unusually, the cave is enclosed within a brick structure rather than left open, and contains a single stone seat beneath a carved symbol — a crown over what has been read alternately as a medallion, a jewel, or a spoon — whose original purpose remains undetermined; one theory holds that the wartime reoccupation was for storing a high-powered searchlight, though this too is unconfirmed.
Decline and Abandonment
Unlike a single factory or institution with one closure date, the Rock’s military fortifications fell out of use gradually and unevenly, as successive technologies made earlier defences obsolete and Britain’s naval and garrison presence shrank in the postwar decades. Some tunnel sections and batteries were maintained for training or storage into the Cold War; others were simply sealed and left, judged too dangerous, too remote, or no longer of any strategic value once the threat they were built against had passed. The result today is a patchwork: a handful of tunnel sections and batteries preserved and opened as visitor attractions, while the majority — including the so-called Lower Galleries and other Second World War sections — remain closed, unlit, and officially off-limits.
What We Found
All the pictures shown here document military installations — bunkers, batteries and observation posts — from both the First and Second World Wars, found across the Upper Rock.
Inside Douglas Cave
Passing along the path, the entrance to Douglas Cave appeared, its brick surround setting it apart from the natural caves nearby. Inside, the carved badge above the stone seat had clearly been cleaned out and painted white at some point, its original surface lost beneath the paint — a small intervention that has done more to obscure the site’s history than a century of neglect.
What Are You Looking For, Bro?
Elsewhere on the Rock, another cave opened into the hillside, dark and unremarkable from outside, one of the many hundred-odd caves recorded across Gibraltar’s limestone mass. The apes were, as always, close by — watching, climbing, occasionally investigating a bag left unattended a little too long, behaving less like wildlife observed at a distance than like fellow residents of the Rock who happened to tolerate the visitors.
Just Chilling
Further along, groups of macaques sat undisturbed on the old fortifications themselves, using ledges and gun positions built for entirely different purposes as places to rest in the sun — abandoned military architecture repurposed, without any particular ceremony, as a nature reserve.
Why Monkeys in Gibraltar?
An earlier theory, since disproven by DNA evidence, held that Gibraltar’s Barbary macaques were a surviving remnant of populations that had ranged across southern Europe during the Pliocene, as long as 5.5 million years ago. Genetic analysis published in 2005 instead traced the colony’s ancestry to founder populations imported from both Morocco and Algeria, most recently during a covert wartime restocking. There is an old superstition, still repeated today, that if the apes ever leave the Rock, the British will follow them off it; Winston Churchill is recorded as having taken the legend seriously enough, in 1942, to order that the macaque population — reduced during the war to as few as seven animals — be replenished from North Africa to keep the old prophecy from coming true. A separate legend holds that the macaques originally reached the Rock through a subterranean passage over fifteen miles long, beginning at Lower St. Michael’s Cave and running beneath the Strait of Gibraltar all the way to Morocco.
Current Status
At the time of writing, in 2026, Gibraltar’s relationship to its own military ruins has shifted noticeably from what is documented above. The World War II Tunnels, a section of the wartime network including the former REME workshop known as Spitfire Hall, reopened in 2025 following a full renovation carried out by a private contractor under the Gibraltar government’s Department of the Environment and Heritage, and further exhibition spaces were added there as recently as September 2025. That renovated stretch, along with the Great Siege Tunnels and select Second World War galleries, is now managed as a paid visitor attraction within the Upper Rock Nature Reserve. The great majority of the tunnel network, however, including the Lower Galleries and sections deemed structurally unsafe, remains closed to the public and is not part of any current restoration plan. No specific published record was found regarding Douglas Cave’s present physical condition beyond what is described above; searches for recent heritage assessments of the cave itself returned nothing more current than general descriptions of its structure and unresolved dating. The Barbary macaque population, meanwhile, is reported by conservation sources as stable or growing, with roughly 300 animals recorded across the Upper Rock as of the most recent published counts.
Urbex location:
