No one knows when the underground cities of Cappadocia were built, perhaps in Hittite times or as late as the 6C AD. There were certainly underground cities as early as the 5C BC. They are referred to by a 5 and 4CBC Athenian historian Xenophon in his Anabasis. So far 36 underground cities have been discovered some of them being very recent. It is also estimated that most of them are connected to each other. But it is difficult to identify these connections.The ground consists of the same volcanic tufa. Cappadocians created vast cities which cannot be noticed from the ground level. They carved airshafts as deep as 85 m / 300 ft into the rock and then made holes laterally at different levels in all directions. They hewed an elaborate system of staircases and tunnels to connect all layers to the surface. They dug dwellings, bathrooms, kitchens, dining halls, storage rooms, wine cellars, chapels, graves and suchlike. In times of danger they provided security by rolling big round hard stones across strategic tunnels. Entrances at the surface were also camouflaged.
Today even from some of the modern houses there are man-made holes leading to underground passages most of which are used as cellars.
Kaymakli Yeralti Kenti (Underground City of Kaymakli)
It is one of the largest underground cities in Cappadocia with eight stories. It covers an area of approximately 4 km² / 1.5 sq mi. Visitors can see only about 10% of the city by going down a maximum of five floors. It probably is connected to nearby Derinkuyu. It was opened to visitors in 1964. The population of Kaymakli is thought to have been about 3,000.
Derinkuyu Yeralti Kenti (Underground City of Derinkuyu)
The underground city of Derinkuyu which means “deep well”, like Kaymakli, is one of the largest. It was opened in 1965. It is 70-85 m / 230-300 ft deep with 53 airshafts. The original ventilation system still functions remarkably well. It is not recommended that visitors having problems of claustrophobia or restricted movement go inside since there are many passageways where one has to squat.
The first two floors under the surface housed a missionary school with two long rock-cut tables, baptismal place, kitchens, storehouses, living quarters, wine cellars and stables. Third and fourth floors were for the tunnels, places to hide and armories. The last floors had water wells, hidden passageways, a church, graves and a confession place.