An entire underground city carved in Turkey once hid 20,000 people from invaders

Beneath the soft volcanic rock of central Turkey lies a labyrinth of carved rooms, stables, chapels and storage halls that once sheltered tens of thousands of people at once. Known today as Derinkuyu, the underground city ranks among the largest and most elaborate refuges ever carved by human hands, built entirely by hollowing out soft stone rather than stacking it.

Carved Into Volcanic Ash

Derinkuyu sits near the town of the same name in Nevsehir Province, part of the Cappadocia region on Turkey’s central Anatolian plateau. The complex descends roughly 85 meters below the surface across multiple connected levels, all cut into tuff, a soft rock formed from compacted volcanic ash that is abundant throughout the region and, crucially, easy to carve with hand tools while still being sturdy enough to hold its shape once shaped. Cappadocia’s underground settlements sit within the boundaries of Goreme National Park and the Rock Sites of Cappadocia, a UNESCO World Heritage property inscribed in 1985 that spans nearly 9,884 hectares between the cities of Nevsehir, Urgup and Avanos. UNESCO’s assessment of the property specifically names Derinkuyu and the nearby Kaymakli underground city among the region’s defining features, describing the wider landscape as one of the world’s largest and most striking cave-dwelling complexes, shaped both by natural volcanic erosion and by centuries of deliberate human excavation.

A City Built in Layers Over Centuries

Tunneling at Derinkuyu likely began with the Phrygians as early as the 8th or 7th century BCE, according to research summarized in the site’s excavation history, though the city as it exists today took shape gradually over more than a thousand years. During the Byzantine era, local Christian communities expanded the original caverns into a deep, multi-level complex, adding chapels, a religious school with a distinctive barrel-vaulted ceiling, and Greek inscriptions carved directly into the rock. UNESCO’s documentation notes that Cappadocian monastic activity dates back to at least the 4th century, when small communities of ascetics began carving cells into the region’s soft rock formations, a practice that laid the groundwork for the far larger defensive complexes that followed. Historians point to the Arab-Byzantine wars, roughly between 780 and 1180 CE, as the period when Derinkuyu likely reached its peak population, as local Christians retreated underground to escape Umayyad and later Abbasid raiding armies moving through the region.

Engineering for 20,000 People

At its largest capacity, Derinkuyu could reportedly shelter as many as 20,000 people along with their livestock and stored food supplies, a scale that required genuine engineering sophistication rather than simple tunnel-digging. The complex included wine and olive presses, stables, storage cellars, communal dining halls and even tandoor-style ovens still recognizable in Cappadocian villages today. Ventilation was one of the hardest problems to solve for a city carved deep underground, and Derinkuyu’s builders addressed it with a network of vertical shafts, including one central shaft roughly 55 meters deep that doubled as a water well, supplying both the underground population and the town above even when the surface was inaccessible during a siege. Engineering analysis published in the journal Rock Mechanics and Rock Engineering found that the shaft openings across different levels were deliberately staggered rather than aligned, a layout that appears designed to maximize airflow through the complex. Massive circular stone doors, operable only from the inside, could seal off individual levels or sections entirely, letting defenders isolate a breach, regroup, and in some recorded cases mount organized counterattacks against intruders who had entered the tunnels.

Rediscovered by Accident in 1963

Knowledge of Derinkuyu’s full scale faded after the Christian population of Cappadocia was forced to leave Turkey in 1923 under the population exchange between Greece and Turkey that followed the end of the Ottoman Empire, and the underground city was abandoned. It remained largely forgotten until 1963, when a local resident renovating his basement knocked through a wall and discovered a hidden chamber leading into the tunnel network beyond. Further digging by archaeologists revealed the full extent of the complex, and more than 600 separate tunnel entrances to the city have since been identified, many concealed beneath the basements of ordinary houses in the modern town above. Even after decades of study, researchers using acoustic and structural surveys continue to document previously unrecorded chambers and passages, and a 2025 acoustics study reported on by the American Acoustical Society used 3D soundscape modeling to reconstruct what the underground chambers may have sounded like when fully occupied.

A Refuge Used Again and Again

Derinkuyu’s usefulness as a hiding place did not end with the Byzantine era. Cappadocia’s underground cities continued to serve as shelters during Seljuk incursions in the 11th century and Mongol raids under Timur in the 14th century, and Cambridge linguist Richard MacGillivray Dawkins, who documented Cappadocian Greek-speaking communities between 1909 and 1911, recorded local residents retreating into the underground chambers as recently as 1909 in response to regional violence. That repeated pattern, of a community returning to the same carved refuge across vastly different historical periods and threats, underscores why Derinkuyu remains such a significant archaeological site. It is not simply a monument to ancient engineering but physical evidence of a defensive strategy that Cappadocian communities relied on, refined and returned to for well over two thousand years, right up until the early 20th century.

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

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