Daredevils in Spain have attempted to walk between two hot air balloons 1,640ft up in the air.

The extreme athletes tried to walk across a slack-line, a tight chord of nylon or polyester, that was tied to the two balloons, on February 1.

Filmmaker Sebastien Montaz-Rosset posted a video of the  attempt on social media sites on February 6, and it is going viral, with more than 700,000 views already.

The extreme athletes are part of a group of extreme athletes,  called Skyliners, who get together to make films of themselves slack-lining in dangerous situations.