Derinkuyu, the largest and deepest underground city in Cappadocia, was founded in 1963 and can house up to 20,000 people. It features multi-level living spaces, schools, churches, and ventilation shafts. The architecture features stone doors and tunnels, showcasing civilization's advancement. Derinkuyu is a popular Turkey tour package from India. https://viztravels.com/turkey-tour/turkey-tour-packages-from-india/