Traveling around Europe by train is about to get a whole lot faster, thanks to the opening of Switzerland’s Gotthard Base Tunnel. It is the product of 17 years of work, including cutting through solid rock at depths of up to 7,500 feet. It cost $12 billion — as well as the lives of eight workers. The project also marks the removal of one of the continent’s most stubborn natural barriers to trade and tourism: the lack of a high-speed route through a mountain range that lies at the crossroads of four countries. The new route has much lower gradients that will allow passenger trains to travel at up to 155 miles per hour, reducing the journey times between Zurich, Switzerland, and Milan, Italy, from just over four hours to two-and-a-half hours.