Zac Vawter Climbs Willis Tower With Bionic Leg

Zac Vawter, a 31-year-old amputee, emerges after walking up the stairs of the Willis Tower in Chicago, Nov. 4, 2012, to become the first person to climb the 103 floors of one of the world's tallest skyscrapers with a bionic leg. (Brian Jackson/Chicago Sun-Times/AP Photo)