Derinkuyu Underground City is an ancient multi-level underground city in the Derinkuyu district in Nevşehir Province, Cappadocia, Turkey. Extending to a depth of approximately 60 meters, it is one of the largest underground cities in the region. It was opened to visitors in 1969 and since then has been a popular historical site. The city includes various rooms, stables, churches, storage areas, and even wine-making rooms, all interconnected by tunnels. It is believed to have been built during the Byzantine era in the 8th–9th centuries to protect the community from invasions. The city could accommodate as many as 20,000 people along with their livestock and food stores. Remarkably ingenious ventilation shafts provided air deep into the underground levels, and large stone doors could block access through the tunnels in times of danger. Exploring Derinkuyu offers insight into the inventive and resilient nature of its ancient inhabitants.