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World’s Deepest and Longest Train Tunnels: The Underground Giants You Won’t Believe Exist

World’s Deepest and Longest Train Tunnels: The Underground Giants You Won’t Believe Exist
photo: Billy69150 / Wikimedia Commons / Public domain / CC BY-SA 4.0/Eurotunnel; illustrative photo
01 / 02 / 2025

Rail transport continues to modernize, but some railway masterpieces have been in place for decades. Among them are railway tunnels—let’s take a look at the five longest ones in the world.

The Longest Railway Tunnel in the World: Gotthard Base Tunnel

The world’s longest railway tunnel is located in Switzerland. It is called the Gotthard Base Tunnel, and it holds the top spot with an impressive length of 57 kilometers. Construction began in 1996, but the tunnel was not opened until 2016.

The tunnel consists of two separate tubes, spaced approximately 40 meters apart. The Gotthard Tunnel runs extremely deep underground—one section lies 2.3 kilometers below the summit of Piz Vatgira mountain. This engineering marvel plays a key role in both passenger and freight transport. Thanks to its high-speed rail connection, travel time between Zurich and Milan has been reduced by an hour. However, it is even more significant for cargo transport, allowing companies to move goods from the port of Rotterdam to southern Europe with greater efficiency.

In 2023, the tunnel suffered an accident—sixteen freight wagons derailed, damaging about eight kilometers of the tunnel, which RAILTARGET previously reported about. Passenger trains were unable to run for months, and freight transport was significantly restricted. The tunnel fully reopened in September 2024, after nearly thirteen months of repairs.

Japan Takes Second Place

Asian countries are ahead of the rest of the world in the use of modern railway technologies, and rail tunnels are no exception.

Japan began work on one of its greatest engineering achievements as far back as 1971—the Seikan Tunnel. Interestingly, the construction of this tunnel was preceded by a maritime tragedy that claimed over a thousand lives. The tunnel is 53.85 kilometers long, with 23.3 kilometers running beneath the seabed at a depth of 100 meters.

The Seikan Tunnel connects the Japanese islands of Honshu and Hokkaido, which were previously accessible only by boats or airplanes. In 1954, a typhoon struck a ferry, resulting in Japan’s worst maritime disaster—the sinking of a ship now referred to as Japan’s Titanic, according to SubstackWhat makes this tunnel even more unique is the presence of two underground railway stations—Tappi-Katei and Yoshioka-Katei. These stations serve as emergency exits, making them the first railway stops in the world to be located under the sea.

Travel from France to England in Style—Under the Sea

Rounding out the top three longest railway tunnels is the world-famous Eurotunnel. The tunnel connects the French port city of Calais with Folkestone, England. It has a total length of 50.5 kilometers, with 38 kilometers running under the English Channel, making it the longest underwater tunnel of its kind. The tunnel consists of two separate tubes and was opened to the public in 1994. Today, it is one of the most popular ways to travel between France and the UK.

Each tunnel accommodates a train specifically designed for transporting vehicles. To use it, travelers must complete a registration form specifying the time and type of vehicle they will be driving through. Arrival at the terminal is required two hours before departure, with check-in and customs clearance mandatory before boarding. Vehicles must enter the tunnel 25 minutes before departure, and passengers must remain inside their vehicles for the entire journey.

South Korea Takes Fourth Place

To find the fourth-longest railway tunnel in the world, we must travel to South Korea. Just like the Gotthard Base Tunnel, the Yulhyeon Tunnel was opened in 2016. It is part of the high-speed rail route between Suseo in Seoul and Pyeongtaek in Gyeonggi Province, where trains operate at speeds of 240 km/h.

South Korea originally aimed to build the world’s longest railway tunnel, but it was unable to claim the top spot. Instead, it holds the record for the longest tunnel in its own country, with a total length of 50.3 kilometers—falling just 200 meters short of the Eurotunnel.

China Makes the List with the Sungshan Lake Tunnel

No list of the world’s longest railway tunnels would be complete without China. According to Railway Technology, the Sungshan Lake Tunnel project began in 2013 and was completed in 2016, but passenger operations did not begin until 2017. This tunnel stretches 38.82 kilometers, connecting Jiao and Changping East Station. It plays a major role in intercity transport along the Dongguan–Huizhou railway corridor. The tunnel features six underground stations, offering passengers multiple boarding options along the route. Trains race through the tunnel at speeds of 200 km/h, making it an integral part of China’s high-speed rail network.

Source: Railway Technology, Substack; iDnes.cz; Denik.cz

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