China's newest feat, a bridge too clear?

China has a thing for glass-bottom footbridges, which seem to be gleefully constructed with the intention of frightening visitors while at the same time reassuring them all is well.

The highest and longest glass-bottomed bridge in the world opened in Hunan province on Saturday.

Spanning 430 meters across Zhangjiajie Canyon, it is 300 meters high and features 99 panes of three-layered glass (each layer about 5 centimeters thick) as its walkway.

Designed by Israeli architect Haim Dotan and built by China Construction Group, the bridge is wedged between two mountain cliffs in Zhangjiajie park. The mountain range is said to have inspired James Cameron's 2009 film Avatar.

A maximum of 8,000 visitors (paying 138 yuan, or $21, apiece) are allowed to traverse the bridge daily, which is about 6 meters wide, and 800 are allowed on at one time. There are three other glass bridges in the Tianmen Mountain in the Zhangjiajie scenic area - including the "heaven seeking avenue", which takes hairpin turns around cliffs.

Before the bridge opened, 20 volunteers were given the chance to swing sledgehammers at the glass bottom to test its sturdiness. It withstood the pounding.

As for how the new bridge stacks up with some in North America, the Grand Canyon Skywalk in Arizona is about 21 meters long and 220 meters above the canyon's bottom.

"Visitors of the Grand Canyon Skywalk can walk over the western rim of the Grand Canyon on a clear, glass-floored structure built to withstand over 71 million pounds (32,200 metric tons) of weight, and experience the sensation of seeing the canyon fall straight away below their feet," the attraction's website says.

The Glacier Skywalk in Alberta, Canada, which opened last year, is 400 meters long. It extends 35 meters from a cliff and is 280 meters above ground.

If you weren't scared enough, the Zhangjiajie bridge will offer the highest bungee jump in the world. (The current title-holder is the 233-meter Macao Tower.)

I think my concern with crossing these bridges would not be because they have glass bottoms but how stable the supporting cables are, for instance, when it gets windy.

So what is the attraction to such a dizzying attraction?

"It is the relationship between emotionally driven fear and the logical understanding of safety," architect Keith Brownlie told the BBC in January. "These structures tread the boundary between those two contrasting senses, and people like to challenge their rational mind in relation to their irrational fear."

Uh, that fear isn't always irrational. Another glass-bottom walkway in China, this one attached to the side of a mountain in Henan province (1,080 meters above the ground) cracked as tourists were crossing in October 2015.

"I yelled out loud, 'It cracked, it really cracked', then pushed the people in front of me to leave. (I was) terrified," a young woman posted on a micro-blogging site, the Daily Mail reported.

Yuntai Mountain scenic spot management said that staffers had noticed some cracks near the exit of the 400-meter walkway. A sharp object falling onto the glass was blamed for the cracks, but management said there was no cause for alarm because there are three layers of glass. (I hope sledgehammer-swinging isn't allowed at Yuntai Mountain).

Contact the writer at williamhennelly@chinadailyusa.com