One of the characteristics of Cappadocia is having plenty of underground cities. It's known that there are more than a hundred of underground settlements in the region and many of them are not open for visits. The underground cities, which are guessed to be used since the Bronze Age, used to be a settlement mostly in Byzantine period, doubtless. In this period, increasing invasions forced local residents to build underground cities for protection and religious purposes.
Kaymakli Underground City
Certainly the most interesting features of the Cappadocia area are the underground cities founded within. Until now even that have been determined about 40 underground cities just six of these have been opened for visit. Nobody can know how many underground cities there are in the Cappadocia area. Some say that there is one for every village and settlement in the region but certainly not all of the sites can be described as cities. Well known underground cities of Cappadocia area are Tatlarin Underground city Derinkuyu Underground City, Ozkonak Underground City, Mazi Village Underground City, Kaymakli Underground City and Gaziemir Underground City
Derinkuyu underground city
The first inhabitants of Cappadocia area have opened deep cavities within the volcanic rocks due to escape from the attacks of the wild animals and hard winter conditions and then they have enlarged these cavities according to their daily needs, they opened new cavities and created the underground cities connecting these cavities with tunnel and labyrinths. Later the underground cities were the place of the hiding of the first Christians who escaped from the persecution of the Roman soldiers and were enlarged to able when were necessary an entire city to live and every kind of fixture necessary for the living of the people has been attached. When there wasn't any danger the people living on the ground in case of the danger have hidden in the underground cities. For this reason all the homes at that time were connected to the underground cities with a tunnel.
Tatlarin Underground City
In all of the underground cities there are ventilation chimneys reaching place by place to a depth of 80 and until the underground waters. These chimneys were opened due to meet the need of both the ventilation and water. Within the cities that are tepid in winters and cool in summers there are kitchens, cribs, wine houses, depots for cereals, meeting saloons, toilets shortly every kind of living space necessary for living. Within all the cities there are locking stones which can be opened and closed only from inside against to the threats which may come from outside.
The oldest written source about underground cities is the Anabasis named book of Xenophon (Written around B.C. 4). In the book is mentioned that the people living in Anatolia have caved their houses underground and that the houses are connected to each other with holes: "The houses were built underground; the entrances were like wells but they broadened out lower down. There were tunnels dug in the ground for the animals while the men went down by ladder. Inside the houses there were goats, sheep, cows and poultry with their young..."