A journalist wears slippers as he walks out on the glass floor of "Step(s) into the Void," an installation at the peak of Aiguille du Midi in the French Alps. | (REUTERS/Robert Pratta)

Tourists brave the view from the the skywalk that extends over the Grand Canyon in Arizona. | (REUTERS/Robert Galbraith)

A reporter leans over the edge of a catwalk during a media preview for the "EdgeWalk" on the CN Tower in Toronto. | (REUTERS/Mark Blinch)

A young girl looks down from "The Ledge," at Chicago's 110-story, 1,450-foot Willis Tower. The glass balcony juts out four feet from the Sears Tower's 103rd-floor Skydeck. | (AP Photo/Kiichiro Sato, File)

A man looks down from a viewpoint in Cabo Girao, on the Portuguese island of Madeira. The viewpoint, a balcony with a see-through glass floor, stands 1,900 feet above the sea level. | (AP Photo/Joana Sousa)