Derinkuyu Underground City (Turkey)
An ancient underground city carved out of the soft volcanic tuff of the Cappadocia region, believed to have been able to shelter thousands of people across multiple underground levels for extended periods. It was equipped with ventilation shafts, wells, stables, storage rooms, and even worship spaces, and is thought to have been connected by long tunnels to the nearby KaymaklΔ± underground city. The commonly accepted view is that it was built and expanded to hide for long periods from invaders or wartime turmoil.
Coober Pedy (Australia)
A desert town in Australia famous for opal mining, where daytime temperatures are so extreme that many residents live in underground homes carved into the earth, known as "dugouts." The underground extends beyond housing to churches, hotels, and shops, meaning a substantial part of the town's daily life happens below ground β a practical way of life that developed both to escape the intense heat and to make use of the space already excavated during mining.
Montreal's Underground City (Canada)
Also known as RΓSO, Montreal's underground pedestrian network connects subway stations, shopping malls, offices, and university buildings via indoor passageways, forming one of the largest underground city spaces in the world. Its defining feature is that it has expanded over decades to let people move through much of downtown without ever needing a coat, even in Canada's harsh winters, and new sections continue to be connected today.
Toronto PATH (Canada)
A massive underground pedestrian network connecting Toronto's subway stations, office towers, and shopping areas, often cited as one of the largest underground shopping and pedestrian spaces in the world. Sources vary somewhat on its exact total length or number of shops, but they commonly agree that tens of kilometers of passageways densely link the downtown underground. Along with Montreal's underground city, it is considered one of North America's premier underground pedestrian networks.
Beijing Underground City, "Dixia Cheng" (China)
A network of air-raid-shelter-style underground tunnels built during the Cold War era to prepare for large-scale bombing, with some sections having been opened to tourists at various points. Although built for that purpose, it was fortunately never needed for full-scale wartime use, and has since been repurposed at times as storage or lodging space. However, which sections are open, and whether they are open at all, can change depending on the period, so anyone planning a visit should check the latest information separately.
Why were underground cities built at all
The reasons vary by region β a hideout to escape war or invasion, housing to escape extreme climate, or a pedestrian network to move around a city center despite brutal weather. The common thread is that when the surface environment becomes difficult or dangerous to live in, people have actively turned to underground space as an alternative. Today, discussions about developing underground space to address extreme climates or crowded city footprints continue in many cities around the world.