Derinkuyu is an ancient multi-level underground city located in the Cappadocia region of Turkey. It was carved from soft volcanic rock and could accommodate thousands of people. The city features various rooms, including living spaces, kitchens, and storage areas, as well as ventilation shafts and wells for water supply. Dating back to the 8th century BCE, Derinkuyu was used as a refuge during invasions and conflicts. Its intricate design allowed inhabitants to live underground for extended periods, with the ability to seal entrances for protection. Today, it is a popular tourist attraction, showcasing the ingenuity of ancient civilizations.