Derinkuyu: an underground city for twenty thousand people

Derinkuyu in central Turkey descends about eighty-five metres through some eighteen levels. It could shelter thousands of people — estimates run to twenty thousand with their livestock and supplies — and it was rediscovered in 1963 when a man knocked through a wall of his house.

It is one of over two hundred underground settlements in Cappadocia, and it is a good example of a site that needs no mystery because the real explanation is more impressive.

Why it was possible

Geology. Cappadocia is covered in tuff — volcanic ash consolidated into rock that is soft enough to carve with hand tools and hardens on exposure to air.

That combination is unusual and it is the whole reason these settlements exist. Digging is feasible with simple tools, and the result is structurally sound. The same rock produces the region’s distinctive eroded landscape.

What it was for

Refuge. The doors are the clearest evidence: circular stone slabs, up to half a tonne, which roll across passages and can only be moved from the inside.

That is not a design for living. It is a design for hiding from something that comes, and then leaving when it has gone.

Cappadocia sat on a frontier that was fought over repeatedly — by Persians, Romans, Arabs, and later others. The sites were used and extended over a very long period, with substantial use by early Christian communities during Arab-Byzantine warfare.

The dating question

Genuinely difficult, and worth stating honestly. Carving rock removes material rather than depositing it, so there is little stratigraphy and nothing organic to date from the excavation itself.

Dating relies on associated finds, on textual references — Xenophon describes underground dwellings in the region in the fourth century BC — and on architectural features such as chapels. Origins are usually placed with the Phrygians or earlier, with major expansion in the Byzantine period.

Why it deserves more attention than it gets

Because it is one of the largest human excavations of the pre-modern world and it was made by ordinary communities over generations, for the entirely comprehensible purpose of not being killed.

There is no puzzle about who or why. There is a genuinely remarkable feat of collective engineering by people whose names are not recorded, which is the usual situation and rarely treated as impressive enough.