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35 miles long, this Swiss monster is the longest tunnel in the world. Miners are risking death right now as billions of pounds of mountain bear down on them -- hot, young rock, 120 degrees F., tough, shifting and unstable. Engineers are using custom-designed TBMs (Tunnel Boring Machines) 250 feet long, 33 feet in diameter, with 500-pound drilling heads that are changed from inside the machine so miners don't get killed outside by cave-ins. In this subterranean world, rock actually explodes. Walls crumble, floods erupt, mud flows. Laser imaging helps engineers see dimly ahead to potential fractures and cave-ins, but they're working in hell. Once a section is dug, concrete walls are thrown up to keep it from collapsing, but if the concrete dries too fast, it implodes under the pressure and the mountain drops on them. Unfortunately, Alpine tunnels stay dangerous forever. In the last two years, truck collisions have turned three of them into infernos, killing 220 people. To most of the wor