In 1963, a vast underground city was unearthed in Derinkuyu, Turkey. The discovery continues to perplex archaeologists. For Ancient Astronaut theorists, it aligns with ancient accounts from the region attributing the construction to a flying god who warned people of an impending catastrophe. Once considered unique, similar underground cities have since been found, such as the Longyou Grottos discovered in Zhejiang Province, China, in 1992.