National Geographic Image Collection / Alamy

Grand Canyon Skywalk, AZ

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Twelve-and-a-half inches of reinforced glass is all that separates the brave souls who walk this four-year-old horseshoe plank from a 4,000-foot plunge into the Colorado River below. —Erin Florio

Coolest New Landmarks Around the World

Grand Canyon Skywalk, AZ

Twelve-and-a-half inches of reinforced glass is all that separates the brave souls who walk this four-year-old horseshoe plank from a 4,000-foot plunge into the Colorado River below. —Erin Florio

National Geographic Image Collection / Alamy

Coolest New Landmarks Around the World

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