WATCH: For highliners Lukas Irmler and Pablo Signoret, an ascent up two frozen waterfalls is only a prelude to the main action: traversing the space between two Alpine peaks.

Two men in the French Alps scaled two frozen waterfalls with 400 pounds of gear to anchor one end of a slackline into each one.

While that might sound like a feat on its own, their goal was actually the space between two alpine peaks, where they performed gymnastics feats on the slackline, more than 500 feet above the ground.

The men, highliners Lukas Irmler and Pablo Signoret, are a climbing team who had been planning this adventure for years, with support from a few other team members who joined them to help them set up. In a secret location near Grenoble, France, the team attached a 1,400-foot slackline between the two waterfalls—an especially challenging location for the sport.

After waiting several days for the right conditions in a shelter they dug, the weather finally cooperated, and the two men were able to go up onto the slackline, a nylon strip that stretches with the walker's weight.

A drone captured footage of their amazing feats in progress. The pair of highliners even stopped occasionally to lie down on the strip, fully immersing themselves in the grandeur of the mountains.

“Usually, a highline is on top of everything,” says Pierre Chauffour, who filmed the stunt. “But here, it was attached in the middle of a gigantic ice waterfall. It makes you feel even smaller than what you’re used to while being in such places.”

Chauffour says it was one of the most challenging highlines the team has rigged.

“They had to ice climb to access the line, which is not usual nor easy,” he says. “There was a risk that the ice [would] melt, but as it was -15°C, it was ok.”

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