It was conceived 63 years ago by Swiss engineer Eduard Gruner and was approved 20 years ago by Swiss voters, and when it was finally finished on Oct. 15 after 14 years of construction, the Gotthard Base Tunnel took the title of the world's longest underground passage. It's a $10 billion, 35.4-mile (57 km) tunnel through the Swiss Alps that now connects Europe's high-speed rail network and lessens the journey between Zurich and Milan by nearly two hours. The tunnel surpassed the length of the 33.4-mile (54 km) Seikan rail tunnel in Japan, which connects the islands of Honshu and Hokkaido.