Underground cities, from ancient hideouts to modern hubs, showcase human ingenuity. In Turkey’s Cappadocia, Derinkuyu’s multi-level tunnels housed thousands, with ventilation shafts and stone doors for defense. Ancient sites like Malta’s Hypogeum and Petra’s tombs used rock-cut architecture and water systems like qanats for survival. Today, Coober Pedy’s cave homes beat desert heat, while Montreal’s […]