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PHOTOS: The World's Greatest Stunts

Will Nik Wallenda add another by walking over Niagara Falls Friday?

PHOTOS: The World's Greatest Stunts

World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
World's Greatest Stunts
Robbie Knievel during his successful 231-foot jump over the Grand Canyon, May 20, 1999. WATCH WALLENDA'S WALK ON THE FULL EPISODE NOW (John Gurzinski/AFP/Getty Images)
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