Ozkonak Underground City Özkonak Underground City, 12 km from Avanos in Nevsehir is a spectacular example of the construction and engineering skills. Discovered in 1972 by a farmer who noticed the water he would give to his crops seemed to mysteriously drain somewhere into the ground, Özkonak is one of three expansive underground strongholds in the region (including Kaymaklı and Derinkuyu). The Ozkonak Underground City has many different levels made up of volcanic granite. These levels are connected by tunnel and have a communication system, which is unique when compared to the Kaymaklı Underground City and Derinkuyu. Each Carved room in this city had its own ventilation vent as evidenced by the pipes in each level that allowed air flow even after the entirety of these cities were sealed during sieges. Like other settlements in the region, Özkonak includes a water well, ventilation system, wine presses, and rolling stone doors. The largest stone door in Cappadocia (nearly 2 meters tall) is located here. The large floor holes near the exit were used for food storage.