A Selection of the World’s Biggest Underground Structures

Large underground structures can sometimes be an even more impressive architectural feat than large above-ground structures. After all, when you start building downward, you have to deal with a variety of issues, including everything from waterproofing concerns to the sheer weight of the earth. That’s why it’s so impressive to see huge underground structures. Here are just a few of the largest and deepest underground structures in the world today.

The Deepest Subway Station: 346 Feet Deep

Many subway stations are underground, but the deepest subway station in NYC is 173 feet underground. That’s only half of the depth of the Arsenala Station in Kyiv, Ukraine. The town of Arsenala is at the top of a hill, but the stops before and after the town are at ground level. To ensure the subway didn’t have to go up and down the hill every time it ran, the construction crew just built through the hill. Now, the subway stop is the deepest in the world.

The Deepest Basement: 120 Feet Deep

When most people talk about the Sydney Opera House’s architecture, they’re talking about the pieces that are visible above-ground. However, the belowground architecture is just as incredible. The parking garage underneath the Sydney Opera House is technically the world’s deepest basement. However, it’s not just a square, like a typical parking garage. To meet fire regulations, the parking garage utilizes a series of double helix-like underground curves.

The Longest Underground Tunnel: 35 Miles Long

Because the Swiss Alps are huge mountains, most trips throughout the Swiss Alps have required going over these mountainous regions, at least to an extent. The Gotthard Base Tunnel was the first to change that. It’s the first-ever flat route through the Swiss Alps, involving absolutely no elevation climb. About 28 million metric tons of 73 different types of rock were excavated for this tunnel, and at its deepest point, the tunnel reaches a whopping 8,040 feet below the surface, where temperatures can reach 115 degrees Fahrenheit.

The Deepest Building Foundation: 310 Feet Deep

The deepest building foundation in the world is actually not attached to the tallest building in the world. Rather, it’s attached to the Salesforce Tower in San Francisco. The tower is 1,070 feet tall, meaning that the foundation is nearly a third of the building’s height. However, this foundation set new benchmarks for seismic safety. Because San Francisco is so prone to earthquakes, this 310-foot foundation was needed to ensure that the building would be sturdy and safe.

The Biggest Underground City: 18 Stories Deep

When you think of underground architecture, you likely think mostly of modern architecture. However, in the case of the underground cities under Cappadocia in Turkey, underground architecture has been around since around 1200 B.C. In fact, this underground city was once a bustling center. People eventually stopped using it to the point where it was completely forgotten; in 1963, a Turkish man knocked down a wall in his basement and accidentally discovered an entrance. Over time, over 600 entrances were found all throughout the city.

The Deepest Underground Research Center: 7,900 Feet Deep

Underground research centers can be extremely beneficial for scientists who are doing extremely sensitive physics experiments. This is because cosmic radiation can impact these experiments but going at least a mile underground all but negates the cosmic radiation’s impact. The Jinping Research Center in Jinping, China is in a former gold mine, placing it nearly 8,000 feet below the earth. Because it’s in a mountain, scientists can simply drive to the laboratory, reducing the need for complicated descent routines.


Underground architecture is at least as incredible as aboveground architecture. In many cases, people find it even more so. Regardless of why you’re interested in architecture in the first place, taking a look at these incredible architectural finds can be an amazing way to gain respect for the architects, designers, and construction crews involved.