The 31-mile "Chunnel" connecting England to mainland Europe was no small engineering feat, but Switzerland has stepped up the game. On June 1, it will begin testing trains in the world's longest, deepest tunnel—and the $12 billion Gotthard Base Tunnel cuts through solid rock as deep as 7,500 feet beneath the Alps and runs a whopping 35.5 miles long, reports NBC News. "It is an incredible project, a huge achievement," says geotechnical engineer Claire Smith, editor of Britain's Ground Engineering magazine. Allowing passenger trains to travel up to 155mph, the twin tunnels (one for each direction) should reduce travel times between Zurich and Milan from four-plus hours to 2.5, not to mention reduce pollution as it shifts traffic from trucks to trains and more than doubles the hauling capacity on the region's north-south freight corridor to at least 44 million tons.
The whole project, which now surpasses Japan's 33.5-mile Seikan tunnel as the world's longest, took 17 years to build and cost the equivalent of the 2012 London Olympics, as Swiss Info reports, as well as the lives of eight of the 2,600 workers. The giant boring machines themselves were as long as four soccer fields. German Chancellor Angela Merkel, French President François Hollande, and Italian PM Matteo Renzi will gather at a ritzy ceremony to inaugurate the new route, which is set to open to passengers in December. It isn't until 2020, however, that the tunnel's full benefits will be realized when an opening at Ceneri allows trains to haul tractor-trailers as tall as 13 feet, reports the Rail Journal. For American comparisons, the tunnel houses enough concrete to span the height of 84 Empire State buildings, and is roughly 20 times longer than Boston's 1.5-mile "Tip" O'Neill Tunnel. (Speaking of world records, Mt. Everest doesn't even break the 20 tallest mountains in the world using this metric.)