The steps are slick with salt. A late-January cold snap has glazed the walkway in thin ice, and a sharp wind rises from the canyon floor, cutting clean through thick winter clothes.

"Walk on the sides," guide Shi Xiuzhi cautions her guests. Behind her, suspended hundreds of meters above the floor of the Dehang Grand Canyon is the Aizhai Bridge, a 1,176-meter sweep of steel and cable.

When it opened in 2012 in the Xiangxi Tujia and Miao autonomous prefecture in western Hunan province, it was one of the longest suspension bridges in the world to span a canyon.

"When I was a student, it took me four or five hours to get home from school," Shi says, recalling life before the bridge was built.

"My grandparents had never been to the city. Back then, it seemed that the birds couldn't fly out of these mountains."

The mountains have never been easy to cross. In the 1930s, as war swept across China, a "wartime lifeline" was carved into these cliffs. More than 2,000 laborers, carrying their own food and tools, spent seven months chiseling out what became the Aizhai Highway.