Ozkonak Underground City Özkonak Underground City, located 12 km from Avanos in Nevşehir, is an impressive example of ancient construction and engineering skills. The city was discovered in 1972 by a farmer who noticed that the water he used for his crops seemed to be disappearing mysteriously into the ground. Özkonak is one of three extensive underground strongholds in the region, alongside Kaymaklı and Derinkuyu. The city comprises multiple levels made of volcanic granite that are connected by tunnels and feature a unique communication system, unlike the Kaymaklı Underground City and Derinkuyu. Each room in the city has its own ventilation vent, evidenced by pipes on every level that allowed for air flow even after the cities were sealed during sieges. Similar to other settlements in the area, Özkonak has a water well, ventilation system, wine presses, and rolling stone doors. It also boasts the largest stone door in Cappadocia, which is nearly 2 meters tall. Large floor holes near the exit were likely used for food storage.