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The Swiss Alps have always posed a formidable barrier to European transport . For centuries , merchants and travellers navigated steep mountain passes , and later , early rail networks struggled against severe gradients . To resolve this bottleneck , Switzerland embarked on an unprecedented project : constructing a railway path directly through the base of the Saint - Gotthard Massif . At 57 kilometres , the resulting Gotthard Base Tunnel is the longest railway tunnel in the world . Rather than climbing over the mountains , trains travel on a flat gradient only slightly above sea level . This design allows heavy freight trains to cross the Alps with far less locomotive power . Boring through the Alps meant operating under as much as 2 , 300 metres of solid granite . At that depth , the pressure is immense , and the rock behaves unpredictably . What engineers had to control was not just the shifting stone , but the extreme subterranean heat . Without ventilation , temperatures inside the rock can exceed 46 degrees Celsius . To manage the excavation , crews worked simultaneously from several access points , using massive tunnel boring machines . Over the course of the digging phase , these machines excavated roughly 28 million tonnes of rock . Much of this material was subsequently recycled and used as concrete aggregate for the tunnel lining itself . The defining moment of the excavation occurred in October 2010 , when the two primary boring machines finally met deep inside the mountain . Rarely in civil engineering does a two - directional excavation achieve such precision over such a vast distance . The horizontal deviation between the two bores was a mere 8 centimetres . Shifting European freight traffic from road to rail was the primary motivation behind the infrastructure . By removing thousands of heavy goods vehicles from Alpine roads every day , the tunnel significantly reduces carbon emissions . The flat trajectory also cuts the travel time between Zurich and Milan by nearly an hour . The tunnel officially opened to regular traffic in 2016 , following more than two decades of planning and construction . The final cost exceeded 12 billion Swiss francs . It was the Swiss public who ultimately funded this endeavour , having approved the financing through a direct national referendum . Have you ever travelled through a major mountain tunnel ? Do you think large - scale rail projects like this are the best way to handle international freight ?
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