If this video doesn't help you understand why slackliners do what they do, then nothing will.
Shot on a GoPro Hero 3, it begins with tranquil music and footage of a few dudes -- members of the group Slack and Run -- hiking through sunny mist near Trois Salazes, a group of three jagged rocks that shoot 6,890 feet above the jungle on the island of La Réunion.
These rocks are really jagged. Like "only room for one person walking on top of them, balance-beam style" jagged. It's a crazy thing to do, but somehow the video makes you realize that to these guys, extreme danger is worth the chance to feel completely alone in an uncharted jungle.
At 2:47, the friends set up their slackline and start a tightrope walk between the rocks. It's only a seatbelt-thick band, their bodies, and nearly 7,000 vertical feet of sprawling tropical jungle. There are tricks (3:27, 3:56), wobbles (3:46), and falls (3:04, 3:17). Every second is a stunning man-meets-nature experience.
But slacklining is not about the stunts, you realize in the end. It's about getting as close to nature as humanly possible, with nobody else around.
...most of us just feel safer doing it on the ground.