Derinkuyu, Turkey
Derinkuyu, in Cappadocia, is an ancient underground city dating back to the 8th century BC. It spans 18 levels and could house 20,000 people. The city features ventilation shafts, wells, kitchens, schoolrooms, etc.

A view of Derinkuyu, Turkey
Photo: @AliceNebularis/x
A view of Derinkuyu, Turkey
Photo: @AliceNebularis/x
