THE TERM BOULDERING, with its connotations of unroped monkey play on low rocks, scarcely conveys the skill and athleticism required for this century-old climbing discipline, which has exploded in popularity over the past 20 years, thanks in part to the development of high-quality foam-and-nylon crash mats. Top boulderers practice a bouldering route—or “problem”—for days, weeks, or even months, repeatedly falling onto the pads, learning the nuances of every handhold, rehearsing body positions, and then putting it all together to make “the send.” In 2010, two new boulder problems were awarded the highest grade possible: V16. These were the first such problems identified in the U.S.; only a handful of other, equally difficult tests have been proposed elsewhere in the world.

The first of the climbs—the Game, an eight-move line in Colorado, on the underside of a prominent talus block below Boulder Canyon’s Cob Rock—was completed by Daniel Woods on February 10, 2010; it has since been repeated and downgraded to V15. The other, Lucid Dreaming, on the Grandpa Peabody boulder outside Bishop, California, was sent by Paul Robinson on March 30, 2010. His remains the only successful climb, and though the 24-year-old Robinson has said Lucid Dreaming might be only a V15, he’s certain that it’s the hardest thing he’s ever done. Robinson worked on the climb over a three-year period, falling hundreds of times during practice trips made from his home in Boulder, Colorado.

Many people watched Robinson rehearse the route, but he finally nailed the ascent without witnesses or cameras. Any chance he’s lying? No way. Thanks to Robinson’s track record and his frequent presence on the rock, the only doubts have been expressed in a few snarky comments in the blogosphere. Here’s how he pulled it off.