Unveiling the subterranean world: cities and tunnel systems below

28 November 2025

Read time: 8mins

‘Subterranean cities – from ancient refuges to modern commercial complexes – are never random. Their existence is a direct response to, and interaction with, their local geography.’

Ty Fields

The world beneath our feet is a labyrinth of human engineering and history, from ancient refuge sites to modern transit hubs. While some subterranean networks are official, commercially active complexes, others are informal, hidden worlds where people seek shelter and community away from the surface.

Despite being one of the most intriguing interests and aspects of human and physical geography, underground cities are still mostly ignored in traditional classrooms. The ‘underground advantage’ is becoming more and more important to engineers and urban planners, although the Earth’s surface continues to get the majority of scholarly attention. This exclusion represents a lost chance for geography educators to teach environmental determinism, human adaptation, and volumetric space.

Geographical significance of subterranean development

Subterranean cities – from ancient refuges to modern commercial complexes – are never random. Their existence is a direct response to, and interaction with, their local geography.

Physical geography: the bedrock of necessity

Subterranean settlements are a testament to the relationship between human activity and geological structure. They occur where the underlying rock permits.

• Ancient cities (Turkey, Italy): the massive underground complexes in Cappadocia, Turkey (e.g. Derinkuyu), were only possible because of the region’s soft, easily carved volcanic tuff rock. This geology provided both ease of excavation and excellent thermal insulation, allowing ancient civilizations to create deep, multi-level cities for refuge and protection from extreme temperatures. The same principle applies to cities like Orvieto, Italy, built into soft volcanic rock.
• Modern complexes (Canada, Australia): modern subterranean spaces are often responses to climatic extremes. Montreal’s RESO network, stretching over 32 kilometers, is a human adaptation to extreme cold, creating a liveable, interconnected urban core beneath the harsh winter surface. Conversely, in Coober Pedy, Australia, the majority of the population lives in ‘dugouts’ carved into the soft soil to escape the blistering desert heat, demonstrating a direct geographical imperative for subsurface life.

Human geography: territory and marginalisation

The subsurface is more than just infrastructure; it’s a contested political and social territory that challenges conventional notions of land use.

• Spatial politics: the study of subterranean territory forces geographers to consider vertical/volumetric space as a resource. Projects like SubTropolis in Kansas City, the world’s largest underground business complex in a former limestone mine, demonstrate the economic use of below-ground space for climate-controlled warehousing. This is a crucial lesson in how resource availability (mined-out space) dictates economic geography.
• The geography of marginalisation: the informal tunnels beneath Las Vegas and New York City, inhabited by the ‘mole people’, represent an extreme form of urban marginalisation. These populations utilise neglected infrastructure (storm drains, abandoned tunnels) as a refuge, illustrating a hidden social geography driven by poverty, homelessness, and the rejection of surface society. They are a reflection of an unequal spatial politics, where the most vulnerable live in the deepest, most dangerous voids of the urban environment.

Mapping the depths: software tools of subterranean exploration

Mapping the invisible world beneath the Earth’s surface requires specialised technology and sophisticated software. Engineers, surveyors, and utility professionals use a combination of hardware and software to create accurate models of subterranean structures:

• Geographic information systems (GIS): core to subterranean mapping, GIS software like QGIS (which can receive live data from mapping platforms) is used to create, analyse, and visualise spatial data. It allows utility data, like the location of pipes, cables, and tunnels, to be accurately overlaid on above-ground maps and topographical information.
• Utility location and detection software: this software is paired directly with hardware like ground-penetrating radar (GPR) and electromagnetic locators (EML). The software interprets the raw data collected in the field to determine the exact location, depth, and type of underground assets.
• 3D modelling and visualisation software: these tools are crucial for creating three dimensional models of utility networks and infrastructure projects. They help engineers visualise the spatial relationships between different subterranean features and the surface.
• Mobile and field data collection platforms: specialised mobile apps that allow field teams to capture, view, and update asset information with centimetre-level precision in real-time, often with full offline capability.

Informal subterranean communities: the ‘mole people’

The term ‘mole people’ is widely known, often referring to homeless individuals who live in abandoned railway, subway, sewage, or storm drainage tunnels beneath major cities. However, this terminology is most prominently associated with the United States, due to publicised accounts of subterranean life in cities like New York and Las Vegas.

Globally, the existence of marginalised communities seeking shelter in the underground is a hidden geographical and social phenomenon. Rather than the sensationalised ‘mole people’ label, other countries use terms that are more descriptive of the local infrastructure they inhabit or the group’s characteristics:

Location	Common reference/name	Description
United Kingdom	Rough sleepers (general term)	While specific individuals may shelter in tunnels, the official and charitable term for those sleeping outdoors or in informal locations is ‘rough sleepers.’ The ‘mole people’ term is not commonly used.
China (Beijing)	Rat tribe (Shuzu)	Refers to millions of low-income migrant workers and students who live in crowded, affordable housing in former Cold War era bomb shelters and basements beneath the city.
Romania (Bucharest)	Bucharest’s tunnel children	Describes the specific population, often orphans or former street children, who established communities in the city’s extensive sewer and heating pipe network, particularly after 1989.
Jamaica (Kingston)	Gully queens/gully dwellers	Refers to a group of marginalised individuals who sought refuge in the city’s storm drains, or ‘gullies’, to escape persecution and seek shelter.
Russia (Moscow)	Homeless/orphans in the sewers	Describes individuals who use the city’s heating ducts and sewers to survive the brutal winter temperatures, sometimes referred to descriptively as ‘sewer people.’

Population estimates in US tunnels

• Las Vegas: the storm drain tunnels beneath the city are reported to house a significant number of homeless residents, seeking shelter from the extreme desert temperatures. Estimates of the population vary, with reports suggesting anywhere from around 300 to 2,000 people living in the flood channels. Reports mention that some individuals have managed to furnish their ‘rooms’ with beds and other comforts.
• New York City: while the most widely publicised accounts date back to the 1990s with the book The Mole People, thousands of people were reported to live in the abandoned subway, railroad, and sewage tunnels. Contemporary sociological accounts portray a diverse group of individuals seeking shelter and a separate existence, though the dramatic claims of underground communities have been subject to factual scrutiny.

Geography and life in the tunnels

These informal settlements are typically found in neglected or active infrastructure, such as:

• Storm drains and flood channels: as seen in Las Vegas, Nevada, these systems provide a network of shelter, but they are incredibly dangerous, particularly during flash floods.
• Abandoned railway/subway tunnels: in New York and other older cities, disused lines and maintenance tunnels offer hidden, out-of-the-way spaces.
• Sewer systems: while less common for long-term habitation due to obvious health risks, segments of older, larger sewer systems have been used.

Life in these tunnels is often characterised by a struggle for basic survival, including the need for lighting, ventilation, and a degree of privacy, with small communities sometimes forming. The stability of the subterranean temperature provides a crucial buffer against surface weather extremes.

Global subterranean cities: size and scope

Subterranean cities on an international scale range from ancient wonders to massive modern commercial and transit complexes.

Subterranean network	Location	Type	Size/Depth/Length
Derinkuyu Underground City	Cappadocia, Turkey	Ancient refuge (c. 1000 BC)	18 levels deeps (approx. 85 meters). Could house an estimated 20,000 people along with their livestock and food stores.
Montreal’s RESO (Underground City)	Montreal, Canada	Modern commercial/transit	Spans 32 kilometres (approx. 20 miles) of interconnected tunnels, covering over 41 city blocks. Connects offices, shops, metro stations, and attractions.
Subtropolis	Kansas City, Missouri (USA)	Modern industrial/commercial	5,100,000 square meters (55 million sq ft) of developed space. It is a massive artificial cave complex used for warehousing and business.
Napoli Sotterranea	Naples, Italy	Historic tunnel network	Covers more than 80 kilometres of tunnels and passageways beneath the city.
Beijing Underground City (Dixia Cheng)	Beijing, China	Former war shelter	A vast network of tunnels and chambers spanning over 33 square miles (85 sq km).
Helsinki Underground	Helsinki, Finland	Modern public shelter	Connects a large underground surface with facilities and bunkers capable of sheltering all 630,000 residents of Helsinki in an emergency.

Potential tourist risks in subterranean spaces

While formal, guided tours of historic and commercial subterranean sites (like the Cu Chi Tunnels in Vietnam, Derinkuyu, or Montreal’s RESO) are generally safe due to modernisation, lighting, and controlled access, unguided exploration of abandoned or unauthorised tunnel systems carries extreme danger.

Underground space is multidisciplinary, touching on geology, engineering, and history, but it often lacks a clear home in the geography syllabus.

• Engineering vs. geography: the planning and construction of subterranean spaces (subways, utility tunnels) is often relegated to civil engineering and architecture studies, not core geography. The need for a dedicated focus on underground oriented education has been recognised by urban planning and technical experts, but it has yet to filter into general geographic learning.

By integrating the study of subterranean cities, geography can offer a powerful, holistic lesson in human-environment interaction – showing how geology dictates settlement, how climate drives necessity, and how human ingenuity creates complex, hidden worlds beneath our feet.

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© Ty Fields, and the Geographical Association, 2025