38.3736°N, 34.7300°E.
Underground city in the volcanic tuff of Cappadocia, central Turkey. The complex extends to a verified depth of approximately 85 metres across at least 18 levels (eight excavated, accessible to the public), with capacity for an estimated 20,000 people plus livestock. Features include ventilation shafts up to 55 metres deep, stables on the upper levels, kitchens with smoke channels designed to disperse exhaust, communal halls, churches, schoolrooms, wineries, and 600-kg circular millstone doors that could be rolled into place to seal entrances from the inside. Construction is conventionally dated to the Phrygian period (8th–7th century BCE); Christian use is documented from the 4th century CE through the Mongol invasions. The city is connected to Kaymakli, 9 km away, by a known tunnel; satellite radar suggests further unmapped systems.
The city was rediscovered in 1963 when a Turkish homeowner knocked through a basement wall during renovations — and found a hallway that went down for fifty metres.