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.
Derinkuyu in numbers
Estimates differ by source, but Derinkuyu is often described as reaching a depth of roughly 60 to 85 meters, with a capacity reported as high as 20,000 people along with livestock and food stores. It was rediscovered in 1963, according to the usual account, when a resident renovating his home broke through a wall and found a hidden room. Dating is uncertain: the earliest tunnels may go back to the first millennium BC, with major expansion during the Byzantine period. Reports of an 8 to 9 kilometer tunnel to nearby Kaymakli are widely repeated, but you should treat the exact length as an estimate.
Why Cappadocia is ideal for digging
The region sits on volcanic tuff, a soft rock formed from compressed ash that is easy to carve with simple tools but hardens when exposed to air. That geology allowed people to excavate rooms, stairs, and passages with limited technology. Large rolling stone doors, which could be closed from the inside, are among the best-known defensive features at sites like Derinkuyu.
Living in a Coober Pedy dugout
Coober Pedy was founded in 1915 after opal was discovered, and it still has a small population of roughly one and a half thousand people at the 2021 census. Summer temperatures often exceed 40 degrees Celsius, while dugouts remain at a fairly constant temperature year-round, so residents save on air conditioning. The town supplies most of the world's gem-quality opal, and visitors can tour underground churches, museums, and accommodation.
Montreal RESO by the numbers
The network began in 1962 with the Place Ville Marie development and now stretches for about 32 kilometers of passages connecting around ten metro stations as well as offices, shops, hotels, and universities. Estimates of daily users vary, but figures near half a million people are often cited. It is a response to winters that can be harsh enough that being able to cross downtown indoors is a real comfort.
Toronto PATH by the numbers
PATH has roughly 30 kilometers of walkways and more than 1,200 retail fronts across about 371,600 square meters, as listed in 2016 when Guinness World Records named it the largest underground shopping complex. It traces its origin to a tunnel built by the Eaton's department store in 1900, and it links dozens of buildings and subway stations. Guinness World Records has since listed Montreal's roughly 32 km RESO as the largest pedestrian subway network (2023), so the title depends on how you measure.
Beijing's Dixia Cheng: scale and status
Construction began in 1969 under orders from Mao Zedong during a period of tension with the Soviet Union, and continued through 1979. Published descriptions suggest an enormous area, in the tens of square kilometers, at depths of around 8 to 18 meters, but the authorities have not released a full account of its extent. A portion was opened as a tourist attraction in 2000, though reports indicate that official tours stopped around 2008, so a visit today is not something you should assume is possible.