The Underground City of Derinkuyu

During my visit to Cappadocia, I explored the fascinating underground city of Derinkuyu. It is believed to have been built in the 8th century by early Christians seeking refuge from persecution. The complex consists of multiple levels, with tunnels, rooms, and even a church. It was a remarkable feat of engineering and architecture, with intricate ventilation systems and stone doors that could be closed to defend against intruders. I compared this underground city with other human-made underground structures I have encountered before and found it to be extraordinary.