Beneath the streets we walk every day, under the noise of traffic and the glow of neon lights, lies an entire secret world most people never think about: underground cities. These vast networks—some ancient, some modern, some still functioning—tell a story of human resilience, fear, creativity, and adaptation. Learning more about them means uncovering layers of history and engineering that often remain forgotten below the surface.
Many people imagine underground spaces as simple basements or subway tunnels, but some subterranean cities are so extensive that they once housed thousands of people for months at a time. Take Derinkuyu in Turkey, one of the most famous examples. This underground metropolis, carved into soft volcanic rock more than 1,500 years ago, had room for up to 20,000 inhabitants. It included chapels, kitchens, wine cellars, stables, and even complex ventilation shafts. What’s fascinating is not just its scale but its purpose: these underground cities were created as sanctuaries in times of invasion, allowing entire communities to vanish—literally—into the earth.
But underground cities are not relics of ancient history. Some are surprisingly recent or still active today. In Montreal, the “RESO” system connects over 30 kilometers of subterranean passageways linking shopping centers, metro stations, hotels, and office towers. Locals use it to escape harsh winters, and despite being entirely under the city, it feels almost like a parallel universe with its own rhythm. Similarly, in Beijing, a massive network of underground shelters built during the Cold War era still exists, some parts repurposed into homes, shops, and hostels.
There are also underground cities built out of necessity rather than fear. In Australia, the mining town of Coober Pedy sits under a relentless desert sun. Temperatures can soar past 45°C, making surface living almost impossible. So residents built their homes, churches, and even bars underground. Visiting the town feels like stepping into a strange hybrid of modern life and cave dwelling, yet people there live perfectly normal lives—just under a few meters of rock.
One often forgotten detail about underground cities is the level of sophisticated engineering required to make them livable. Ventilation has always been one of the biggest challenges below ground. Ancient architects solved this problem with ingenious systems of shafts and openings that allowed fresh air to circulate, even through many levels. Modern underground complexes rely on advanced climate control to prevent humidity and stale air, and some even simulate daylight using LED technology that mimics the sun’s natural spectrum. This is especially important in places like Helsinki, where an entire underground infrastructure includes sports halls, data centers, and emergency shelters, all designed to remain functional under extreme conditions.
Another overlooked aspect is how underground spaces are often shaped by the threats of their time. Some were built to escape invaders, others to survive nuclear fears, and more recently, to adapt to overcrowded cities. As urban populations grow, architects and planners increasingly look downward for solutions. Tokyo, Singapore, and Helsinki are pioneers of “subsurface urbanism,” where city planning includes multi-layered underground networks designed to ease congestion, protect against natural disasters, or expand usable space without altering the skyline.
When we think about cities, we usually look upward at skyscrapers, high-rise apartments, and towering monuments. But the real intrigue sometimes lies below us, in the buried tunnels, chambers, and corridors that hold centuries of human stories. Exploring these underground cities reminds us that the world is not only wider than we imagine—it’s also deeper. The next time you walk through a subway station or pass an unassuming basement entrance, consider what might lie beneath. Entire cities may be hidden in the dark, waiting for their stories to be rediscovered.
