Derinkuyu reaches 85 meters (280 feet) below the surface and sheltered up to 20,000 people during invasions. The engineering includes ventilation shafts running the full depth, rolling stone doors, stables, living quarters, communal dining, a cross-shaped underground church, and multiple food storage areas. On the upper levels, find the rectangular carved stone troughs - these are wine presses. The Christian Greeks hiding down here brought their entire food economy underground, and wine was essential infrastructure, not an afterthought. Enter and descend as far as permitted (usually 8 levels). Notice that wine/food storage areas are on the upper levels (first in, first used) while living quarters are on the lower levels (safest from attack).
🔄 BACKUP: Ask the guide about the 8-9km underground tunnel connecting Derinkuyu to Kaymaklı - they functioned as one interconnected underground society.