The Derinkuyu underground city is a multi-level refuge carved into the soft volcanic rock beneath the town of Derinkuyu in Nevşehir Province, central Turkey. It reaches an estimated 60 to 85 metres below the surface and is thought to have sheltered up to roughly 20,000 people, together with their livestock and food stores. Its earliest levels are usually attributed to the Phrygians of the 8th–7th centuries BCE, and it was greatly enlarged in the Byzantine era by Christian communities who used it as a refuge from raids.
Derinkuyu matters because it is one of the largest excavated underground complexes known anywhere, and because no one can say with certainty when its first chamber was cut. That gap between what can be seen and what can be documented has made it a fixture of ancient-mystery television and a genuine research problem for archaeologists. This guide sets out what the site contains, what the written record says, what mainstream scholarship concludes, and where alternative readings, including Billy Carson's, fit into the picture.
Where is Derinkuyu and what is it carved from?
Derinkuyu is a town in the Cappadocia region of central Anatolia, and its Turkish name means “deep well.” The underground city lies directly beneath the modern town and is one of the components of the UNESCO World Heritage property “Göreme National Park and the Rock Sites of Cappadocia,” inscribed in 1985.
The key to the whole region is its geology. Over millions of years, eruptions from volcanoes including Erciyes Dağı and Hasan Dağı buried the Cappadocian plateau under thick deposits of ash that consolidated into tuff and ignimbrite. This rock is soft enough to be cut with simple iron hand tools, yet cohesive enough to hold open rooms, corridors and stairways without timber supports. The same stone produced Cappadocia's famous fairy chimneys and the thousands of rock-cut churches, homes and dovecotes that dot its valleys.
That context matters for everything that follows. On this plateau, digging into the ground was not an exotic engineering feat. It was the cheapest and most practical way to create durable, insulated space, and people in Cappadocia did it for thousands of years.
What is inside the Derinkuyu underground city?
Derinkuyu is a vertical complex of multiple levels, eight of which are accessible to visitors, joined by narrow, low passages and steep stairways. Rather than one great hall, it is a honeycomb of rooms of different sizes and functions stacked on top of one another.
The upper levels hold the spaces that needed to stay closest to the surface, including stables for animals. Deeper down are storage cellars, wineries and oil presses, communal rooms and living quarters. More than 50 ventilation shafts carry fresh air to the lowest levels, and some of the deep shafts reached groundwater and doubled as wells, allowing the population to draw water without going outside.
Two spaces stand out. One is a large hall with a barrel-vaulted ceiling, traditionally called the “missionary school.” The other, on a lower level, is a cruciform room, laid out in the shape of a cross, that is generally identified as a church. Both belong to the Christian phase of the site's use.
The rolling stone doors
The most distinctive features are the great circular stone doors. Up to about 1.5 metres tall and weighing around 500 kilograms, they sit in recesses beside the passages and could be rolled across to seal a corridor. Crucially, they could only be closed from the inside. The people underground, not the people above, controlled who came in. Combined with passages so low and narrow that anyone entering had to stoop and move in single file, the doors show that the complex was designed above all for defence.
Who built Derinkuyu?
The honest answer is that no inscription or building record names the first builders, so every date is an inference from context. The Turkish Ministry of Culture and Tourism attributes the earliest levels to the Phrygians, who dominated much of central Anatolia in the 8th–7th centuries BCE and were skilled at working rock. Some scholars have proposed that the first cuttings go back further still, to the Hittites of the 2nd millennium BCE, but direct evidence for a Hittite phase is lacking.
Dating a rock-cut space is unusually difficult. Carving removes material rather than adding it, so there is no mortar, timber or foundation deposit to date. Worse, each generation that used the complex enlarged, re-cut and cleaned the rooms, erasing the tool marks and debris left by earlier users. What survives is mostly the last phase of use, laid over whatever came before.
That last phase is well understood. From roughly the 5th to the 10th century CE, Byzantine Christian communities expanded the complex dramatically, and the church, the vaulted hall and much of the layout visible today reflect that period.
What the ancient texts say
The oldest text usually cited is Xenophon's Anabasis, written in the 4th century BCE. In Book IV, Xenophon describes villages in the Armenian highlands of eastern Anatolia where the houses were dug into the ground, entered through an opening like a well, and shared by the families and their livestock. The passage describes a region well to the east of Cappadocia, so it is not a description of Derinkuyu itself. It is, however, strong evidence that subterranean living was an established Anatolian way of life more than two thousand years ago.
Why was Derinkuyu dug?
The mainstream explanation is that Derinkuyu was a refuge: a place where an entire community could hide with its animals and supplies when danger passed through. Anatolia sat on the path of armies and raiders for most of recorded history, and an underground city was a way to survive a raid without abandoning the land.
The Byzantine period supplies the clearest example. During the long Arab–Byzantine wars, Cappadocia was a frontier zone repeatedly crossed by raiding forces, and the local Christian population is thought to have retreated underground when raids came. Sealable doors, internal wells, ventilation, food stores and stabling all fit that purpose: the goal was to outlast a threat that would eventually move on.
Climate offered a second, everyday reason. Underground rooms hold a far more stable temperature than the surface, which suits the storage of grain, wine and oil and offers relief from the plateau's hot summers and harsh winters. Many Cappadocian households used rock-cut cellars for exactly this reason long after the threat of raids had passed.
The complex stayed in use for a very long time. Cappadocian Greeks were still using the underground spaces into the 20th century, until the 1923 population exchange between Greece and Turkey removed the Greek Orthodox communities of the region. After that, much of the complex fell out of use and out of memory.
How was Derinkuyu rediscovered?
Derinkuyu was rediscovered in 1963, when a local resident renovating his house knocked through a wall and found a passage behind it. The passage led into a network of rooms that turned out to be far larger than anyone expected. Clearing and study followed, and the underground city opened to visitors in 1969. It has since become one of the most visited sites in Cappadocia.
Derinkuyu, Kaymaklı and Cappadocia's other underground cities
Derinkuyu is not unique; it is the best known of more than 200 underground settlements identified across Cappadocia. They range from a few connected rooms beneath a village to full multi-level complexes.
Its closest neighbour is the Kaymaklı underground city, and the two are reported to be linked by a tunnel about 8 kilometres long. Whether or not every stretch of that tunnel was ever passable, the connection fits the refuge model: communities that could move between shelters, or share them, were harder to trap.
The list keeps growing. In 2013 and 2014, urban renewal work around Nevşehir castle exposed another underground complex, which Turkish officials have described as potentially larger than Derinkuyu. Excavation there is a reminder that the full extent of Cappadocia's underground world is still not mapped.
The alternative theories about Derinkuyu
Derinkuyu's scale and uncertain start date have made it a favourite of alternative-history writers, and several distinct claims circulate. They should be understood as claims, set alongside the archaeological picture rather than in place of it.
The most widely broadcast, popularised on television programmes such as Ancient Aliens and among some readers of Zecharia Sitchin, holds that the city was built as a shelter from a threat from the sky. A second claim links the underground cities to the climatic upheaval that some researchers place around 12,900 years ago, arguing that people dug down to survive a sudden cold period; the evidence for and against that event is covered in our guide to [the Younger Dryas impact hypothesis](/the-younger-dryas-impact-hypothesis-explained-the-evidence-for-and-against). A third proposes that a lost, earlier civilisation cut the first levels, pointing to the fact that Anatolia hosted monumental construction far earlier than once believed: [Göbekli Tepe](/gobekli-tepe-explained-oldest-temple-in-the-world), in the southeast of the country, is more than 11,000 years old. Derinkuyu also features in wider discussions of subterranean worlds, which our explainer on [hollow earth theory](/hollow-earth-theory-explained-from-halley-to-agartha-and-what-science-shows) examines from Halley to Agartha.
The mainstream response is straightforward. No artefacts from the Ice Age or the early Neolithic have been reported from Derinkuyu, and nothing in the complex points to an aerial threat. The features that can be dated, such as the church, the wineries and the stone doors, match known historical periods. And because tuff is easy to carve, a very large complex does not require advanced technology, only many hands over many generations.
It is also fair to note what that response cannot settle. Because the earliest levels were re-cut repeatedly, the date of the very first excavation remains technically open, and that open question is the space the alternative theories occupy. Readers weighing those arguments may find it useful to set Derinkuyu beside the broader question of [whether ancient civilisations had advanced technology](/could-ancient-civilizations-have-had-advanced-technology).
Billy Carson's reading
Billy Carson treats Derinkuyu as one example of a global pattern rather than a local curiosity. In his view, underground refuges on several continents point to ancient populations responding to cataclysm, people who expected a threat severe enough to justify moving an entire community below ground and who built accordingly.
Carson connects that pattern directly to Egypt, and in particular to the tunnels and chambers he discusses beneath the Giza plateau. For him, Derinkuyu and the spaces under Giza belong to the same story of a deep human past that is only partly recorded in conventional history. That is his interpretation, not the scholarly consensus, which continues to read Derinkuyu as a refuge from raids and a practical response to the local climate and geology. Readers who want the Egyptian side of the argument can start with [our guide to the Giza plateau and what lies beneath it](/the-giza-plateau-explained-a-visitors-guide-to-the-pyramids-sphinx-and-what-lies-beneath).
What both readings share is the recognition that Derinkuyu is an extraordinary achievement of human planning and labour, and that its earliest chapter has not yet been written with certainty.
Watch, read and go deeper
Billy lays out his case for a hidden world beneath Egypt in the podcast episode Underground City Discovered Under the Giza Pyramids. On 4BK TV, the series [Ancient Enigmas](/watch/ancient-enigmas) and [Unsolved](/watch/unsolved) explore the sites and open questions that sit on the edge of mainstream history. For the wider context of ancient origins, the [Anunnaki topic hub](/topics/anunnaki) gathers Billy's articles, episodes and reading on the earliest civilisations.
Frequently asked questions
How deep is the Derinkuyu underground city?
Estimates put the deepest parts of Derinkuyu at roughly 60 to 85 metres below the surface. The complex is arranged on multiple levels, and eight of them are open to visitors. Exact figures vary because not every part of the complex has been fully cleared or surveyed.
How many people could live in Derinkuyu?
The usual estimate is up to about 20,000 people, along with their livestock and food stores. That number is an estimate based on the size of the complex, not a recorded population. The city was designed for temporary shelter during danger rather than permanent everyday living.
Who built Derinkuyu?
No record names the original builders. The Turkish Ministry of Culture and Tourism attributes the earliest levels to the Phrygians of the 8th–7th centuries BCE, and some scholars suggest earlier Hittite origins without direct evidence. The complex was greatly expanded by Byzantine Christians between roughly the 5th and 10th centuries CE.
Can you visit Derinkuyu today?
Yes. Derinkuyu has been open to visitors since 1969, and eight levels can be explored. The passages are narrow, low and steep in places, so visitors who are uncomfortable in confined spaces should be prepared.
Is Derinkuyu connected to Kaymaklı?
Derinkuyu is reported to be linked to the nearby Kaymaklı underground city by a tunnel about 8 kilometres long. Both are among more than 200 underground settlements identified across Cappadocia. The connection fits the view that these complexes were part of a regional network of refuges.
Sources and further reading
- Xenophon, Anabasis, Book IV, translated by Carleton L. Brownson (Loeb Classical Library).
- UNESCO World Heritage Centre, “Göreme National Park and the Rock Sites of Cappadocia,” inscription of 1985.
- Turkish Ministry of Culture and Tourism, site information for the Derinkuyu Underground City.
- Spiro Kostof, Caves of God: Cappadocia and Its Churches (Oxford University Press).
- Robert G. Ousterhout, A Byzantine Settlement in Cappadocia (Dumbarton Oaks, 2005).
- Robert G. Ousterhout, Visualizing Community: Art, Material Culture, and Settlement in Byzantine Cappadocia (Dumbarton Oaks, 2017).
