Strange History

Derinkuyu: Inside the 18-Story Underground City Found Behind a Basement Wall in Turkey

By The Unsolved Report Editorial Team · Last reviewed 2026-06-19

Derinkuyu is an ancient underground city in Cappadocia, Turkey, carved 85m deep. What we know, the open questions, and the myths about its builders.

In 1963, a man in the central Anatolian town of Derinkuyu knocked down a wall during a home renovation and found cold air pouring out of the gap. Behind the wall was a room. Behind the room was a passage. And behind the passage was a city - one that plunged dozens of meters into the volcanic rock beneath his feet, with chapels, stables, kitchens, wine presses, and ventilation shafts threading down through the earth. He had reopened Derinkuyu, the deepest excavated underground city in Cappadocia, a place that may have sheltered as many as twenty thousand people and their livestock.

That origin story is repeated everywhere, sometimes with embellishments. So let us do what this brand does: separate the documented record from the open questions from the fringe.

What we can prove

Derinkuyu sits in Cappadocia, a region of central Turkey famous for landscapes of soft volcanic tuff. That geology is the whole story. Tuff is soft enough to carve with hand tools yet hardens on exposure to air, which makes it ideal for digging livable spaces underground. Cappadocia is riddled with such sites; more than two hundred underground settlements of at least two levels have been documented in the region, and Derinkuyu is simply the deepest yet excavated.

According to the Wikipedia entry on Derinkuyu, the site descends roughly 85 metres (about 280 feet) and is often described as having around 18 levels, though only a portion is open to visitors. It could reportedly hold up to 20,000 people together with their food stores and animals. The complex includes a 55-metre ventilation shaft that doubled as a well, barrel-vaulted rooms, a cruciform church on a lower level, wine and oil presses, stables, refectories, and storage cellars.

Its most striking defensive feature is a series of large circular stone doors. These rolling stones, some weighing several hundred kilograms, could be moved across a passage from the inside and locked in place, sealing a level against intruders. The doors are a clever piece of asymmetric design: they could be operated easily by the defenders standing behind them, but an attacker on the far side had no handhold and little leverage, and the narrow corridors meant only one or two people could approach at a time. A small hole through the center of some doors may have let defenders thrust a spear at anyone trying to force the stone. Crucially, each floor could be closed off independently, so a section could be defended even if an upper level was breached.

Derinkuyu is also not alone. It is connected by several kilometers of tunnels to the nearby underground city of Kaymakli, and the wider region around the modern town of Goreme is a UNESCO World Heritage Site recognized for its rock-cut architecture. That regional context is important. Derinkuyu is not a freak one-off but the deepest and most elaborate member of a whole tradition of underground living in Cappadocia, where the same soft tuff that made the famous fairy-chimney landscapes above ground also invited people to dig downward.

How a whole city hides underground

The practical genius of Derinkuyu is its life-support engineering. Air is the obvious problem: tens of thousands of people and animals breathing in a sealed warren of rock would quickly suffocate. The builders solved this with a network of vertical ventilation shafts - more than fifty are reported - that pulled fresh air down through every level and that could draw water from the deep aquifer. Wells were placed so they could be accessed from inside without exposing the inhabitants to anyone above ground, and some were reportedly sealed off from the surface entirely to prevent enemies from poisoning the supply.

The layout reads like a town turned vertical:

Upper levels held stables and living quarters, where ceilings were lower and ventilation easiest.
Middle levels contained communal spaces - a reported religious school with a barrel-vaulted ceiling, churches, and storage.
Lower levels held wells, a dungeon, and a large cruciform church.

This was not a place to live full time. It was a refuge. People lived above ground and descended into the earth when danger came, sealing the rolling doors behind them. Carbon dioxide buildup, food spoilage, and the sheer psychological strain of darkness all set practical limits on how long a population could hold out below. The design priorities tell the story plainly: this is architecture optimized for surviving a siege of days or weeks, not for permanent comfort.

Consider what it would have taken to keep twenty thousand people and their animals alive underground even briefly. You need air, water, food storage, sanitation, lighting, and a way to keep livestock from panicking in the dark. Derinkuyu addresses each of these. The deep shafts handled air and water. Cool, stable underground temperatures preserved grain, oil, and wine. Stables near the surface kept animals where ventilation was best. Oil lamps provided light, and the soot-darkened ceilings in places still record their use. It is a complete, if grim, life-support system carved from rock.

The genuine open question: who built it, and when

Here is where confident histories start to wobble, and where honesty matters most.

The most commonly cited claim is that the Phrygians, an Iron Age people, began the excavations in roughly the 8th to 7th century BC. The Phrygians were certainly active in Anatolia and were capable rock-cutters, so the attribution is plausible. But it is not airtight. Dating excavated rock is genuinely difficult: carving removes material rather than depositing it, so there is little organic matter to radiocarbon date, and later occupants reused and reshaped earlier spaces. Some scholars push the earliest workings back toward the Hittite era; others are more cautious and treat the deep origins as uncertain.

What is better attested is the later history. The site was substantially expanded in the Byzantine period, when Christian communities in Cappadocia faced raids during the Arab-Byzantine wars. The chapels, the cross-shaped church, and Greek inscriptions point clearly to Byzantine Christian use as a hiding place from invading armies. Centuries later, local Cappadocian Greeks reportedly still used the underground cities to shelter from periodic persecution, up until the population exchanges of the early 20th century.

So the responsible summary is this: Derinkuyu was very likely begun in antiquity, possibly by Phrygians, and was demonstrably enlarged and used as a refuge by Byzantine-era Christians. The precise identity of the first diggers and the exact start date remain unresolved.

There is a deeper methodological point worth dwelling on, because it explains why the mystery persists. Most archaeological dating depends on stratigraphy - reading the layers of deposited material that accumulate over time - or on radiocarbon dating of organic remains. An underground city resists both. Carving is subtractive: it removes rock rather than laying down datable layers. Any organic material found inside, such as charcoal or grain, tells you when someone used a space, not when it was first cut. And because each generation reshaped what the last had built, the earliest surfaces may have been carved away entirely. Derinkuyu is, in a sense, a palimpsest in stone, with the oldest writing scraped off to make room for the new.

What the evidence rules out

Derinkuyu attracts a lot of speculation, and some of it deserves a firm but fair pushback.

You will sometimes read that the city is impossibly ancient - tens of thousands of years old - or that it was built by a lost advanced civilization, or even linked to aliens or to shelter from some prehistoric cataclysm. There is no evidence for any of this. Everything recovered from the site, from the architectural style to the Christian chapels and Greek inscriptions, fits comfortably within known Anatolian history. The engineering is impressive, but it is human-scale impressive: ventilation shafts and rolling doors are clever, not anachronistic.

The famous 1963 discovery story is broadly accurate but often dramatized. Locals knew of underground spaces in Cappadocia long before 1963; what the renovation uncovered was a major new section of the network. The town's name itself - Derinkuyu means roughly deep well in Turkish - hints that the deep shafts were never entirely forgotten.

Why it still matters

Strip away the embellishment and Derinkuyu becomes more impressive, not less. It is a monument to a recurring human experience: the need to disappear. For people living along contested frontiers, where armies and raiders came without warning, the ability to vanish an entire community underground - with water, food, livestock, and a place to pray - was the difference between survival and annihilation.

The real mystery of Derinkuyu is not who carved it with the help of impossible technology. It is the quieter, more human question of exactly how many centuries of fear and ingenuity it took to hollow out a city beneath a plain - and how many times its rolling stone doors swung shut while danger passed overhead.

The bottom line

Derinkuyu is real, deep, and genuinely remarkable, and most of the wild claims about it are unnecessary. The documented engineering and Byzantine refuge history are extraordinary on their own. The honest open question is the identity and exact date of its first builders - a question that the soft, undatable rock may never fully answer.

Sources & further reading

Wikipedia - Derinkuyu underground city - https://en.wikipedia.org/wiki/Derinkuyu_underground_city
Wikipedia - Goreme National Park and the Rock Sites of Cappadocia (UNESCO) - https://en.wikipedia.org/wiki/G%C3%B6reme_National_Park_and_the_Rock_Sites_of_Cappadocia
UNESCO World Heritage Centre - Goreme National Park and the Rock Sites of Cappadocia - https://whc.unesco.org/en/list/357/
HISTORY - Why Is There a Massive Ancient City Hidden Beneath Turkey - https://www.history.com/articles/derinkuyu-turkey-underground-city
Big Think - Derinkuyu: Mysterious underground city in Turkey found in man's basement - https://bigthink.com/strange-maps/derinkuyu-underground-city/