What is the longest underground tunnel in the world?

The Gotthard Base Rail Tunnel, completed on October 15, 2010, stretches 35.4 miles (about 57 kilometers) under the Swiss Alpine mountains. Its completion pushed the Seikan Tunnel in Japan, at 33.5 miles (about 54 kilometers), to second place. The Gotthard Base Rail Tunnel connects northern Europe to Italy and will shorten the travel time by over an hour when it opens for cargo and passenger trains in 2017. It was a ten billion dollar project that was first conceived about 60 years ago. It took 23 years of digging and the loss of 8 lives for the tunnel to be completed.