12 Cities Built Above Unexplored Caverns
Cities around the world sit atop mysterious caverns, tunnels, and forgotten networks that remain only partially explored.
- Alyana Aguja
- 4 min read
Beneath some of the world’s most bustling cities lie vast subterranean labyrinths shrouded in mystery. From ancient aqueducts in Naples to Cold War shelters in Beijing, these hidden spaces reveal forgotten histories beneath modern life. Despite centuries of study, large sections remain uncharted, suggesting that the world under our feet may be far stranger and more intricate than we imagine.
1. 1. Paris, France
Image from Matador Network
Beneath the elegant streets of Paris lies a vast labyrinth of limestone tunnels and catacombs stretching for hundreds of kilometers. While parts of it are open to tourists, much of the underground network remains sealed and unmapped. Even today, explorers known as “cataphiles” secretly enter these spaces, discovering new chambers that defy official maps.
2. 2. Kansas City, Missouri, USA
Image from KCUR
Kansas City sits atop a sprawling network of limestone caves that were once used for mining and storage. Known collectively as SubTropolis, parts of these caverns are now home to businesses, yet large sections remain uncharted. Scientists and explorers suspect that hidden passageways extend deeper than anyone has yet explored, buried under the city’s industrial sprawl.
3. 3. Naples, Italy
Image from Full Suitcase
Naples is built on a honeycomb of ancient Greek and Roman tunnels carved into soft volcanic tuff. Over centuries, these caverns were used as aqueducts, air-raid shelters, and even secret escape routes. Only a portion has been fully studied; many parts remain sealed behind collapsed walls.
4. 4. Edinburgh, Scotland
Image from Scotland’s Wild
Beneath Edinburgh’s cobblestone streets lies a maze of medieval vaults, cellars, and chambers dating back to the 18th century. These caverns were once home to merchants, outlaws, and plague victims. While some vaults have been restored, vast areas remain closed off and unmapped. Historians believe there are still undiscovered sections, containing remnants of the city’s darker, forgotten history.
5. 5. Beijing, China
Image from Gray Line
Underneath Beijing runs a Cold War-era underground city built in the 1960s as a nuclear fallout shelter. While portions have been opened as tourist attractions, most remain off-limits and poorly documented. Urban explorers say the network is far larger than the official record suggests, stretching beneath modern skyscrapers and ancient temples alike.
6. 6. Istanbul, Turkey
Image from Civitatis
Istanbul, once Constantinople, stands atop an intricate system of Byzantine cisterns and tunnels. The most famous, the Basilica Cistern, is only one part of a vast hydrological maze. Archaeologists have discovered new chambers each decade, but a complete map remains elusive. Some experts believe that forgotten sanctuaries and hidden passageways still snake beneath the city’s historic heart.
7. 7. Seattle, Washington, USA
Image from Visit The USA
The modern city of Seattle was literally built on top of its old self after a devastating fire in 1889. The old streets and storefronts were buried beneath new construction, creating a subterranean city that remains partially unexplored. Some areas are open for tours, but much of it is closed off due to instability.
8. 8. Montreal, Canada
Image from Destination Canada
Montreal’s Underground City, officially known as RÉSO, was intentionally built as a subterranean complex of walkways and shopping centers. However, beneath this modern network lie much older limestone quarries and natural caverns. Many of these spaces have never been fully mapped, as they predate the city itself. Occasional collapses hint at deeper voids still hidden beneath the urban core.
9. 9. Budapest, Hungary
Image from Lonely Planet
The Buda side of Budapest sits atop a system of natural caves formed by thermal waters. Over centuries, these caverns were expanded into cellars, shelters, and even prisons. Many remain sealed or unexplored due to unstable rock formations. Geologists continue to uncover new passages beneath the castle district, revealing layers of history interwoven with the earth.
10. 10. Puebla, Mexico
Image from Inspirato
In 2015, workers in Puebla discovered a vast network of tunnels beneath the city, believed to date back to the 16th century. The tunnels may stretch for miles, connecting ancient convents and plazas. While parts have been excavated, most of the system remains closed and largely unexplored. Local myths speak of lost treasures and secret chambers that lie untouched beneath centuries of urban growth.
11. 11. Odessa, Ukraine
Image from UAmedTOURS
Odessa’s catacombs are among the largest in the world, spanning more than 2,500 kilometers. Originally carved from limestone mines, the tunnels form a chaotic labyrinth beneath the city. Only a fraction has been charted, and many sections remain dangerously unstable. Hidden chambers and blocked passages continue to baffle explorers who risk getting lost in its darkness.
12. 12. Nottingham, England
Image from Goway Travel
Nottingham is famous for the hundreds of man-made caves carved into sandstone beneath the city. These underground spaces served as dwellings, breweries, and hideouts for centuries. While some have been restored, archaeologists continue to find new ones during modern construction. The true extent of Nottingham’s underground labyrinth is still uncertain, buried beneath the rhythm of daily city life.