A hand-dug underground city in Turkey could hide 20,000 people and their animals

Beneath the small town of Derinkuyu in central Turkey lies a city that most residents walked over for centuries without knowing it existed. Carved entirely by hand into soft volcanic rock, the underground complex descends roughly 85 meters and, at its largest, could shelter as many as 20,000 people along with their livestock and stored food. It stayed hidden from the wider world until a resident renovating a basement broke through a wall in 1963 and stumbled into a tunnel network that archaeologists are still mapping today.

Derinkuyu sits in the Cappadocia region, an area shaped by ancient volcanic eruptions that left behind a soft, easily carved rock called tuff. That geology is what made a project of this scale possible without metal excavation equipment, and it is also what has kept the tunnels structurally intact for well over two thousand years.

Carved into soft volcanic tuff

The rock at Derinkuyu is tuff, compacted volcanic ash that is soft enough to carve with basic hand tools but hardens somewhat when exposed to air, giving finished passages more structural stability than the raw material’s softness would suggest. That property let successive generations dig, widen and interconnect rooms over hundreds of years using picks and chisels rather than the metal-cutting tools a project of this scale would otherwise demand. Engineers who have surveyed the site describe a network of vertical shafts and connecting tunnels engineered with enough precision that ventilation channels reach nearly every chamber, a detail that becomes especially significant given how deep the lowest levels sit below the surface.

Eighteen levels of rooms, stables and a church

The complex descends across as many as 18 distinct levels, according to researchers who have surveyed the full network, though only a portion is currently open to visitors. Rooms found throughout the tunnels served specific functions: stables for livestock, wine and oil presses, communal kitchens fitted with tandoor-style ovens still recognizable to residents of Cappadocia today, storage cellars, refectories and even a barrel-vaulted room on the second level that researchers believe functioned as a religious school. A church occupies one of the lowest levels, reached by a staircase system that also allowed each floor to be sealed off independently in an emergency.

A refuge built and rebuilt over centuries

The earliest tunneling at Derinkuyu is generally attributed to the Phrygians, who began carving chambers into the region’s tuff as far back as the eighth or seventh century B.C. The city reached its fullest form much later, during the Byzantine era, when Christian communities in the region expanded the original chambers into the deep, multi-level refuge visible today, adding chapels and Greek inscriptions as they went. Historical accounts describe the underground city sheltering local populations during the Arab-Byzantine wars between roughly 780 and 1180, a period when raiding armies made the tunnels’ concealment and defensibility especially valuable, and it is during this stretch that researchers believe the site’s population came closest to its peak capacity.

Engineering that outlasted its builders

The tunnel system connects to at least one other underground settlement, Kaymaklı, through a passage stretching between eight and nine kilometers, evidence that Derinkuyu was never an isolated project but part of a broader regional network of underground refuges across Cappadocia. Large rolling stone doors, some over a meter thick, could seal individual sections from the inside, letting inhabitants isolate compromised areas or mount organized counterattacks if part of the city was breached. Ventilation relied on a series of shafts of varying width, including one central shaft reaching 55 meters that appears to have doubled as a water well, engineered so that openings on different levels never lined up directly with one another, a layout that seems designed to maximize airflow through the complex.

Abandoned in 1923, rediscovered decades later

Derinkuyu remained in active use by local Cappadocian Greek and Armenian communities into the twentieth century, providing refuge during periods of persecution as late as 1909, according to research conducted by Cambridge linguist Richard MacGillivray Dawkins during his fieldwork in the area. The tunnels were finally abandoned in 1923, when the Christian population of the region was relocated to Greece as part of a large-scale population exchange between the two countries. Knowledge of the specific network at Derinkuyu then faded until that 1963 rediscovery, after which more than 600 separate tunnel entrances were eventually identified, some hidden beneath the basements of ordinary houses in the town above. The site is now protected as part of Goreme National Park and the Rock Sites of Cappadocia, a UNESCO World Heritage property recognized for both its cultural and natural significance.

What makes Derinkuyu remarkable is not just its size but its longevity as functioning infrastructure, expanded and reused across roughly three thousand years by different peoples for the same basic purpose: staying hidden and staying alive when the surface became too dangerous.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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