National Geographic Image Collection / Alamy
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
How we use your e-mail address
© 2014 Time Inc. Affluent Media Group. A part of the Time.com sites. All rights reserved.