How the Gotthard Tunnel was drilled through 35 miles of granite

The Gotthard Tunnel, which opened June 1, is a 35-mile railroad tunnel at the base of the Gotthard Mountain in Switzerland. It is the newest part of a rail system that now connects Zurich with Milan. Construction began 17 years ago, with 30-foot-diameter drilling machines that cut through the mountainside at a rate of 20 to 25 meters per day, removing a total of 24 million tons of rubble. This video is an animation showing how the drilling machine works.