Karl Wallenda (the grandfather of Nik Wallenda) doing a tight-rope walk across Veterans Stadium. Wallenda did this on August 13, 1972. Shockingly, Wallenda would actually sit down on the wire while in the middle of the walk and motion to Veterans Stadium workers that the rope had to be more taut. Even more incredible: when he went over 2nd base, Wallenda did a headstand!
This photo is courtesy of Sports Illustrated, and you can read the great article from Philly.com about the occasion here.