It's only the biggest (or longest or deepest) one until someone builds an even bigger one. That holds true for so many things, the largest Ferris wheel, the longest suspension bridge, the tallest building, and the list goes on. For now, Switzerland lays claim to the longest and deepest rail tunnel in the world called the Gotthard Base Tunnel.

For thousands of years, the longest tunnel in the world was an ancient Roman tunnel that they built to drain a lake. The tunnels are called the Tunnels of Claudius (after the Roman Emperor) and stretched for 6 kilometers or 3.5 miles. Not all ambitious tunnels that get started, get completed. A forerunner to the English Channel Tunnel (aka Chunnel) started being built in 1880 before the British government put a stop to it out of security concerns.

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The Gotthard Base Tunnel - The World's Longest

The Gotthard Base Tunnel is a twin-born tunnel supplying a high-speed rail link under the Swiss Alps to connect northern and Southern Europe. The tunnel stretches for some 57 km or 35 miles and was planned to take some 1 million trucks off the road so that the cargo can go by train instead.

  • Length: 57 km or 35 miles
  • Depth: Up To 2.3 km or 1.4 Miles Below the Mountains
  • Type: Rail Tunnel
  • Rail Type: High-Speed Rail And Heavy Freight Trains
  • Completed: In 2016

Previously the longest rail tunnel in the world was Japan's 53.9 km Siekan rail tunnel with the famous Channel (at 50.5 km) under the English Channel coming in next.

It is also the deepest tunnel in the world and gets around 2.3 km below the surface of the mountains towering high above. Another dimension of the tunnel is the temperature. The rock can reach a toasty temperature of 46C or 115F.

The rock that the tunnel bored through ranged from as hard as granite to as soft as sugar. In total, some 28 million tonnes of rock were excavated.

The longest tunnel under construction is the Mont d'Ambin Base Tunnel between Italy and France with an expected completion date of 2029. When complete it is expected to be 57.5 km or 37.7 long and will claim the mantel of being the longest tunnel in the world.

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The Swiss Alps and the Need For a Massive Tunnel

The Gotthard Base Tunnel is the third tunnel to be built under the Gotthard - after the Gotthard Tunnel and the Gotthard Road Tunnel. It is considered a base tunnel as it bypasses much of the existing Gotthard railway line (which is a winding mountain route that opened back in 1882).

The Alps, while utterly stunning, are also a major barrier to transport in Europe - especially freight. The tunnel has not only removed untold numbers of trucks from the roads of the Alps, but it has also significantly reduced the danger of fatal road crashes and environmental damage posed by heavy trucks.

  • Reduced: The Tunnel Has Reduced Travel Time, Environmental Damage, and Road Accidents
  • Cost: The Project Cost over $12 Billion
  • Referendum: The Tunnel Was Approved In A Swiss Referendum in 1992

As Switzerland famously has an open-source democracy, it had to be approved in a referendum in 1992. It was approved by 64% of the Swiss voters and the first preparatory work commenced in 1996 with official construction starting in 1999.

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Using The Tunnel Today

The tunnel has better tied the canton of Ticino to the south of the Alps with the rest of Switzerland (which lies mostly to the north of the Alps). A trip from Basel in Switzerland to Milan in Italy has seen around an hour cut off the travel time.

  • How To Travel The Tunnel: Book A Train Through The Swiss Alps
  • Bonus: Travel On A High-Speed Train

If one would like to travel through the tunnel, then remember it is a train-only tunnel. One will need to book a ticket from northern Switzerland (like Basel or Zurich) to southern Switzerland (like Lugano) or Italy (like Milan).

There are more frequent and more convenient services with new and modernized rolling stock that made passenger travel through the tunnel more attractive. The tunnel rail improvements gradually came into being between 2016 and 2020 or so with authorities seeking to make this tunnel the main route.

Today the tunnel stands beside the likes of the Panama Canal and the Channel Tunnel as one of the greatest engineering feats of modern times.