How I climbed a 3,000-foot vertical cliff -- without ropes | Alex Honnold

Imagine being by yourself in the dead center of a 3,000-foot vertical cliff -- without a rope to catch you if you fall. For professional rock climber Alex Honnold, this dizzying scene marked the culmination of a decade-long dream. In a hair-raising talk, he tells the story of how he summited Yosemite's El Capitan, completing one of the most dangerous free-solo climbs ever.