A tunnel is defined as an enclosed underground passageway with no openings except for the ends. They are used for a variety of purposes including water supply, telecommunications, power, road and/or rail traffic. They are used for a variety of reasons, such as when a bridge is not feasible or when a road/railway cannot be diverted around a large mountain. Most tunnels are only a few hundred meters in length, but the longest tunnels can run for many kilometers! Let’s find out which tunnel is the longest in the world.
What is the longest tunnel in the world?
The Thirlmere Aqueduct in England is officially the longest tunnel in the world at a total of 154.5 km (96 mi). It was built between 1890 and 1925 to carry water from the Thirlmere Reservoir to the city of Manchester.
The second longest tunnel in the world is the Delaware Aqueduct in New York state with a total length of 137 km (85.1 mi). It catties water from the Delaware Aqueduct, the West Branch Reservoir, and the Kensico Reservoir. It was built between 1939 and 1945 and carries about half of the water supply for New York City. It also holds the title of being the longest continuous underground tunnel at 120 km (75 mi).
The longest rail tunnel is currently the Seikan Tunnel, which travels beneath the sea in the Tsugaru Strait connecting the two main Japanese islands. It is 53.85 km (33.46 mi) long and 23.3 km (14.5 mi) of this is under the sea floor. This tunnel will soon be eclipsed by the Gotthard Base Tunnel, which is a railway tunnel under the Swiss Alps. It is expected to open in 2016 at a length of 57 km (35.4 mi).