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