Gibraltar's geography: a limestone ridge dug out and built around

Why Gibraltar's area has no single figure

A territory this small ought to have an agreed size, and the figures published as of September 2026 differ by a square kilometre. The English Wikipedia article on Gibraltar gives 6.8 square kilometres, its article on Gibraltar's history gives 6.7, and Britannica prints a total area of 6.5 in its quick facts and 5.8 square kilometres in the body of the same entry. The catalogue's own record rounds the figure to 7.

None of the sources says what its figure includes or when the land was measured. Two things could move it. The 800 metres of the isthmus held by the United Kingdom are disputed ground, and a figure may count them or leave them out. And the land itself has grown: reclamation from the sea ran through the twentieth century and after, so an area taken before one scheme and quoted after it is out of date.

The other dimensions are steadier. Britannica gives the peninsula as 5 kilometres long and 1.2 kilometres wide, joined to Spain by a low sandy isthmus 1.6 kilometres long. The land border with Spain runs for 1.2 kilometres and the shoreline for 12. Gibraltar has no administrative divisions; for planning and statistics it is split into seven Major Residential Areas.

Nothing in those figures leaves room for fields. Britannica records that there is no agriculture on the peninsula, for lack of space, and the whole population is counted as urban, 100% in the 2025 World Bank series the record carries.

What the Rock of Gibraltar is made of

The Rock is a ridge of Jurassic limestone and shale running roughly north to south along the peninsula. Britannica puts its northernmost summit, Rock Gun, at 421 metres, and the highest point at 426 metres near the southern end. From there the ridge shelves down to Europa Point, a relatively flat area ringed by cliffs up to 30 metres high that faces Ceuta across the strait.

The two long sides of the ridge are unlike each other. Seen from the Mediterranean, the east is a run of sheer cliffs dropping to the sea. The North Face, above the isthmus, is a nearly vertical cliff 396 metres high. The western slope is gentler, and it is the only side on which a town could be built: Britannica describes houses rising tier on tier for some 90 metres above the old defensive walls, and above them limestone cliffs that almost cut off the Upper Rock, which is covered in wild trees.

Limestone dissolves, and the Rock is full of caves. The Romans' name for it, Mons Calpe, may come from the Phoenician kalph, meaning hollowed out, and the history of Gibraltar covered in Gibraltar: history begins in those caves. For the geography what matters is what the caves kept. UNESCO, which inscribed the Gorham's Cave Complex in 2016, describes four caves in the eastern cliffs set among fossil sand dunes, fossil beaches and scree slopes, and says the deposits can depict the climate and environment of the peninsula across roughly 120,000 years.

That record shows a different coast. When the polar ice caps were larger the sea stood much lower, and the ridge rose above a fertile coastal plain with marshes and dunes where there is now open water. The east side of Gibraltar is therefore two shorelines at once: the present one at the foot of the cliffs, and older ones preserved in the fossil beaches and dunes of the cave setting. UNESCO lists the property as vulnerable to sea level rise, flooding and other effects of climate change.

How Gibraltar found water without rivers or springs

There are no rivers, no streams and no large bodies of fresh water on the peninsula. The only natural supply was a set of wells in the north, on the isthmus. The ancient settlers of the bay chose the mainland instead, and Carteia, founded by the Phoenicians near modern San Roque, stood at the head of the bay.

For most of the town's history, water was caught as it fell. Wikipedia describes an aqueduct, wells, cisterns, barrels and earthenware pots set out to collect rain. As the population grew in the eighteenth and nineteenth centuries that stopped being enough, and cholera and yellow fever spread through a town where, by one garrison officer's account from the 1860s, more than 15,000 people were confined in a square mile. The sewers were of little use in summer, because there was no water to flush them.

The Board of Sanitary Commissioners, set up in 1865, put the storage inside the Rock. Reservoirs with a capacity of 5 million gallons, about 22.7 million litres, were cut into the limestone. On the east side, the sand slopes above Catalan Bay and Sandy Bay were sheeted over to make a rain catchment, which Wikipedia puts at nearly 250,000 square metres. Rain ran down the sheeting into tanks blasted inside the ridge, and it was blended with water pumped from the isthmus wells or distilled from the sea.

The catchments stopped supplying drinking water in the 1990s, when a desalination plant built in the 1980s was expanded; Britannica records that they still serve as a service reservoir. Drinking water in Gibraltar now comes entirely from desalination. One plant, working by reverse osmosis, was built in a tunnel inside the Rock, and a second, a multi-stage flash distillation plant, stands at the North Mole. A separate supply of seawater is piped for sanitation. Both are held in reservoirs excavated under the Rock.

How the tunnels turned the Rock inside out

Tunnelling began as a military answer to the North Face. In May 1782, during the Great Siege, a party of artificers under Sergeant Major Henry Ince started cutting a gallery towards a protruding rock called the Notch, to cover approaches below the cliff that the guns above could not reach. The Gibraltar Museum records that these Upper Galleries eventually held 17 guns. Thirteen men took five weeks to dig 25 metres. By 1790 there were about 1,200 metres of tunnel inside the Rock.

Twentieth-century tunnelling was far larger. Early in the century the Rock was tunnelled to connect the east side with the west, and Britannica records that the excavated stone reclaimed 26 hectares from the sea. During the Second World War, after the civilian population was evacuated in 1940, the garrison dug more than 50 kilometres of tunnels. The spoil went onto the isthmus to extend the airfield so that it could take bomber aircraft.

In both campaigns one operation made two things: a hole inside the ridge and new ground outside it. Most of the tunnelled roads are still operated by the military and closed to the public, and Britannica also records tunnels within the Rock for vehicular traffic.

How Gibraltar built new land along its shores

The western shore has been moved outward for more than a century. The history of Gibraltar notes that the only land access to the town, a coastal strip about 350 metres wide below the North Face, was considerably narrower before twentieth-century reclamation. From 1889 the Royal Navy built a new harbour and an expanded dockyard on this shore. The port facilities now occupy most of the western shore and a portion of land reclaimed from the sea.

A larger programme followed the reopening of the frontier in 1985, as the territory built for finance, shopping and tourism. The result is that about a tenth of Gibraltar's present land area was reclaimed from the sea, and the 2012 census found that reclaimed land housed more than 40% of the population. Wikipedia gives the usually resident population in 2012 as 32,194, a density of about 4,959 people per square kilometre.

The later figures run higher. The record gives 34,003 as of 1 January 2020, and Britannica gives 38,196 for 2022. The vast majority live on the Westside, the western slope and its reclaimed shore; the East Side holds the settlements of Catalan Bay and Sandy Bay. Population growth was running at 2% in 2025, in the World Bank series the record carries, and Wikipedia records that the demand for space is increasingly met by reclaiming more land.

What lies on the isthmus below the North Face

North of the Rock the ground drops to the isthmus, a low sandy neck 1.6 kilometres long. The southern 800 metres of it are within Gibraltar's territory. Spain holds that this ground was never ceded and the United Kingdom claims it by long possession, and Gibraltar: history sets out both positions; this catalogue takes neither.

The isthmus took the uses that need flat ground. An airfield was laid out on it in 1933, and the tunnelling spoil of the Second World War extended it. The runway and the road north had to share the same neck of land. For decades Winston Churchill Avenue, the main road into Spain, crossed the runway itself, with movable barriers closing it whenever an aircraft landed or took off. A new road and tunnel named Kingsway, passing under the terminal and the eastern end of the runway, opened on 31 March 2023, and the runway is now closed to everyday road traffic.

Beyond the frontier the isthmus continues into the Spanish town of La Línea de la Concepción, in the province of Cádiz. The hinterland is the comarca of Campo de Gibraltar, whose name means the countryside of Gibraltar. The mainland is also where much of Gibraltar's workforce sleeps. The Gibraltar government's budget address counted 13,844 frontier workers in 2024, almost half the workforce. Under the UK-EU agreement applied provisionally from 15 July 2026, the House of Commons Library records, physical barriers on this border can be removed and joint checks move to the port and the airport.

How the strait shapes Gibraltar's wind and sea

Gibraltar sits at the eastern mouth of the Strait of Gibraltar, 24 kilometres from the Moroccan coast. Britannica gives the strait as 58 kilometres long, 13 kilometres wide at its narrowest between Point Marroquí and Point Cires, and 23 kilometres wide at its eastern end between the two Pillars of Hercules, the Rock to the north and a peak on the African side, identified as either Mount Hacho near Ceuta or Jebel Musa in Morocco. The channel averages about 365 metres deep.

Two layers of water move through it in opposite directions. A surface current runs east into the Mediterranean through the centre of the channel, and below about 120 metres a colder, heavier and saltier current flows west into the Atlantic. The eastward flow is the larger, and Britannica's summary is that without the strait the Mediterranean would become a shrinking salt lake.

The wind is funnelled the same way, and it blows either from the east or from the west. The easterly, the levanter, is a shallow, fast, low-level stream of cold air from the north pushed out through the gap, and the territory is exposed to it.

The climate is Mediterranean, classed Csa, with mild wet winters and hot, humid, almost rainless summers. The average daily high across the year is 21.7 °C and the overnight low 15.8 °C. January averages a high of 16.3 °C with the sea at 16 °C; August a high of 28.4 °C with the sea at 22 °C. Wikipedia attributes Gibraltar's comparatively cool summers and steady annual temperature, which it shares with Algeciras and Tarifa, to the strait.

What lives on the Upper Rock of Gibraltar

Most of the Rock's upper area is nature reserve, and it holds more than 500 species of flowering plant. Wild olive and pine grow on the Upper Rock among dense maquis. The Gibraltar candytuft, Iberis gibraltarica, is otherwise native to North Africa and grows wild on the Rock; it is the symbol of the reserve.

The Barbary macaques are the best known of the animals. Three-quarters of the world population lives in the Middle Atlas mountains of Morocco, and the species is listed as endangered. How the Gibraltar group arrived is not settled: Britannica says the animals were introduced possibly as early as Roman times, and Wikipedia cites genetic studies and historical documents pointing to arrival during the Islamic period. In 1944 Winston Churchill sent a message to the Colonial Secretary asking that something be done about their falling numbers.

The group is managed as well as wild. A government statement of 7 May 2026 records that the macaques are fed every day of the year in two feeds, morning and late afternoon, on a diet set by a veterinary surgeon, that a network of purpose-built freshwater ponds has been created for them in the reserve, and that patches of maquis are to be cleared after the bird nesting season to open new foraging ground. The same statement treats illegal feeding by visitors as the main pressure on the animals.

Rabbits, foxes and bats also live on the Rock, and dolphins and whales are frequently seen in the bay. The Barbary partridge lives here and nowhere else on the European continent. Migrating birds are very common. The sea off the east side, below the Gorham's caves, is protected as the Eastern Marine Conservation Zone.