Shanghai’s latest tourist attraction: an outside, rail-less walkway around one of its tallest skyscrapers

The public can never get enough of death-defying diversions, from flagpole sitters in the 1920s to today’s ever-crazier rollers coasters. The last two “Mission Impossible” movies—which featured Tom Cruise actually scaling the outside of the Burj Khalifi and hanging onto the wing of a jet in flight—combined did nearly $1.4 billion in box office sales internationally. And one of the attractions of “extreme” sports and recreation is that the participants live to tell about it.