Kaymakli Underground City in Cappadocia is a fascinating maze of ancient passageways and homes that once sheltered over 3,500 people dating back to the 7th and 8th centuries BCE. Built by the Hittites and Phrygians for protection against invaders, this underground city features nearly 100 tunnels spanning eight levels, with unique structures like churches, wineries, and ventilation shafts. Today, visitors can explore four open levels, experiencing a glimpse into the history and ingenuity of this remarkable subterranean settlement.