This picture, taken in Bosnia and Herzegovina in September, gives new meaning to the term hanging out. These 19 daredevils, suspended more than 650 feet above the Tijesno Canyon, are practicing “hammock highlining,” which combines elements of zip-lining, mountain climbing, and tightrope walking. It was part of the Drill and Chill Climbing and Highlining Festival, an annual gathering of people who love extreme vertical sports, which have gained in popularity over the past two decades. To set up, the participants anchored a line to two mountains across a 260-foot-wide gap and, after attaching safety harnesses, slid out on 17 hammocks; they then hung out for about four hours. So what’s the meaning behind hammock highlining? “They go out there to enjoy the heights, the scenery, and celebrate vertical culture,” says David Lemmerer, one of the festival organizers. “They really just hang out up there. It’s a social thing.”