Turkey’s Derinkuyu could shelter 20,000 people eighteen stories below the ground

Beneath the town of Derinkuyu in central Turkey lies one of the largest excavated underground cities in the world, a warren of tunnels, rooms, wells, and passages carved straight down into soft volcanic rock. At its full extent it descends roughly eighteen levels and, by common estimates, could shelter as many as twenty thousand people along with their livestock and food stores.

The site is not a single chamber but an entire subterranean settlement, complete with the infrastructure a hidden population would need to survive underground for extended periods. Its scale and engineering have made it one of the most studied features of Cappadocia, a region whose geology invited people to dig rather than merely build.

The Cappadocian rock that made it possible

Derinkuyu sits in Cappadocia, a plateau in central Anatolia covered by thick layers of volcanic ash that hardened over millions of years into a rock called tuff. Tuff is soft enough to be cut with simple hand tools yet firm enough to hold its shape once exposed to air, a combination that let communities hollow out homes, churches, and storerooms across the region, as reference accounts of the area describe. The same conditions produced the region’s famous “fairy chimneys” aboveground and, below the surface, a network of carved dwellings and refuges.

Because the stone could be worked downward in stages, an underground complex could be expanded over generations, each era of inhabitants deepening and widening what earlier ones had begun. That accretion helps explain how a site like Derinkuyu reached the size it did.

Eighteen levels and a self-contained design

The city plunges through a series of stacked levels connected by narrow, easily defended passageways, reaching a depth on the order of eighty-five meters. Rather than a random maze, the layout reflects deliberate planning: living quarters, kitchens, storage rooms, stables for animals, wine and oil presses, and even spaces identified as chapels and a school were distributed through the complex.

Crucial to survival underground was ventilation. Derinkuyu was pierced by vertical shafts that circulated air to the deepest occupied levels and, in places, doubled as wells that drew water from below without exposing it to anyone on the surface. That last detail mattered for defense, since a besieging force could not poison a water supply it could not reach.

Rolling stone doors and a city built to be sealed

What separates Derinkuyu from an ordinary cellar network is that it was engineered to be closed off from the inside. At intervals along its corridors sat large circular stone doors, some weighing hundreds of kilograms, that could be rolled across a passage to seal a level. The doors were designed to be operated only from within, so defenders could block an advance while attackers had no easy way to shift the stone from the other side.

The upshot was a settlement that functioned less like a permanent home than like a vast bunker. In times of danger a population could descend, seal the entrances behind them, and live off stored provisions and internal wells until a threat passed, then return to the surface when it was safe.

Who hid there, and from what

The origins of Derinkuyu are debated, with construction sometimes attributed to peoples of the first millennium BCE and expansion continuing over many centuries. What is clearer is how it was used in the Byzantine era, when Cappadocia lay along contested frontiers and its Christian communities faced repeated raids and invasions. During those centuries the underground cities served as refuges where whole villages could shelter through periods of unrest, as documentation of the wider Cappadocian landscape notes.

Living underground for days or weeks at a time was demanding, which is precisely why the complexes included so much infrastructure. The presence of stables, presses, storerooms, and communal spaces indicates that the builders anticipated sheltering not just people but the economic life of a community for as long as necessary.

Connected to a wider underground world

Derinkuyu did not stand alone. Cappadocia contains dozens of underground settlements of varying size, and Derinkuyu is reported to have been linked by a long tunnel to another major complex at nearby Kaymaklı, suggesting a coordinated regional network of refuges rather than isolated hideouts. Rediscovery of Derinkuyu’s fuller extent is often traced to the twentieth century, when work on a surface home is said to have broken through into forgotten passages, prompting renewed exploration.

Today the site is a heavily visited landmark, with a portion of its levels opened to the public while much of the complex remains unexcavated or closed. Its enduring appeal rests on the same qualities that made it effective: the sheer ambition of carving a city downward into rock, and the ingenuity of a design meant to keep thousands of people alive and hidden beneath the surface.

Why the numbers still impress

Estimates of Derinkuyu’s capacity vary, and a figure like twenty thousand is best treated as an informed approximation rather than a precise census, since no one recorded how many people ever actually sheltered there at once. Even so, the point of the figure holds. A settlement able to absorb a population that large, feed and water it, ventilate its lowest chambers, and seal itself against attackers represents a remarkable feat of premodern engineering, accomplished with hand tools and an intimate understanding of the rock.

This article was researched and drafted with the assistance of AI and reviewed before publication.

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