An inconspicous street in Cappadocia extends between Kaymakli and Derinkuyu.
Two huge underworld "cities" are concealed beneath it, both offering a capacity for thousands of people.
It was discovered in 1963, they were used by the Christians in the 7th century as places of refuge
from the advancing muslim crusaders.

Derinkuyu lies 29 kilometers south of Nevsehir. 50 underground cities are assumed to be located
in the region, with 36 of them already located, but only 3 have been made accessible.
Derinkuyu, with the as yet 8 open levels, is one of the biggest. The temperature is constantly at
8 degrees Celsuis. The first underground levels were already used as storage and water depots by
the Hethiters. Further excavations took place in the second half of the 7th century, as cappadochian
Christians had to expand their previous hideouts.
Living and sleeping quarters are available, as well as churches. Escape routes up to the neighbouring
city 9 km away have been found. The most imposing feature is the ventilation system.
15000 chutes take care for the good air down to the 8th floor. Even today, the population acquires
its good-quality water from the old water ducts.

A few entrances to the underworld exist in both the cities Kaymakli and Derinkuyu.
A complex branching of the corridor system (1) in multiple floors (up to 12!)
reaches a dept of 50m. A well thought of arrangement of huge
ventilation channels (2) crosses the cave system. The corridors could
be closed with "millstone doors" (3).

Doubts about the christian refuge theory exist. The ventilation chutes could be easily closed
from above ground. It is probable that the cave cities are older that assumed.

An underground connection between both cities (distance 10 km) could exist! Similar
settlements at Özkanak, Karakören and Catköy are still to be researched.