Haohan Qiao — "Brave Men's Bridge"

The Haohan Qiao bridge in China's Shiniuzhai National Park already had a fearsome reputation. You crossed the slender wooden structure that locals called "Brave Men's bridge" at your peril. And then the park manager decided to take things up a notch. 

In 2014, engineers underwent the unenviable task of replacing Brave Men's wooden slats with glass, allowing visitors to stare directly onto the 590-foot drop. Underneath your now trembling legs are thick panels, 25 times stronger than normal glass. 

Staring down into the abyss is possibly the scariest part of the crossing, but perhaps not the most impressive. At almost 300 meters (980 feet) across, this was the longest glass suspension bridge in the world for a brief time. It connects two peaks in the rocky terrain of the national park in Hunan Province, the region believed to have inspired the film Avatar.  

It didn't hold its title of "world's longest" for very long. In 2016 a 1,400 foot glass bridge was constructed in the nearby Zhangjiajie Grand Canyon, looming twice as high as Brave Men's bridge. These Chinese suspension bridges and other shiny attractions such as the Ledge at the Willis Tower in Chicago and the glass skywalk in the Grand Canyon show how glass adds a novel dimension to the world's wonders.