Zac Vawter Climbs Willis Tower With Bionic Leg

Zac Vawter stands on The Ledge of the Willis Tower in Chicago after walking up the stairs of the building, 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. Vawter became the first person to stair climb wearing a prosthetic leg controlled by his mind. (Brian Jackson/Chicago Sun-Times/AP Photo)