In a sport full of bucket list events, the Hardrock Hundred Mile Endurance Run is one of ultrarunning’s most coveted finishes. Each year a complex three-tier lottery cuts more than 1,000 would-be entrants down to just 150, a number necessitated by the race’s fragile alpine terrain. That fortunate group will start this year’s run in Silverton, Colorado on Friday.

“The course is an intimidating monster,” said Mike Foote, an elite ultrarunner from Montana. Foote was third in 2010 and is expected to challenge for a podium finish at this year’s race.

Hardrock’s 100-mile loop connects a series of mountain towns while gaining nearly 34,000 feet of elevation, all at altitudes that reach as high as 14,000 feet, while never dipping below 7,000 feet in a near constant up and down.

“The altitude, the cumulative elevation gain and loss, and the distance alone demand respect,” Foote said. Add to that the potential for extreme mountain weather, and Foote is “hopeful not to be on top of a peak or pass when the inevitable thunderstorm rolls through.”

That’s exactly what happened to Adam Campbell last year, when he and his pacer Aaron Heidt were caught at the top of the 14,058 Handies Peak about halfway through the race during a storm. A crack of lightning struck so close by, the men were knocked to the ground. Campbell went on to finish third.

“[We] were just in the wrong place at the wrong time and we were both incredibly lucky that neither of us was seriously hurt,” Campbell said. “I would never intentionally run onto a marathon in a lightning storm and know that people get killed every year in similar circumstances.”

Although commonly considered a race, Hardrock is officially titled a run, and its challenges more often turn it into an adventure, and that’s part of the cult-level appeal.

 “I am fully aware that not everything will go perfectly as planned on race day, so it’s exciting to think how I can react to the diversity. This course throws more at you than most, which leaves less time to think about competition,” Foote said. “To be honest, I like this setup far better and it allows me to focus on the things I can control, versus what my competitors are—or are not—doing.”

Anna Frost, who is considered a top contender for this year’s race, said her mind is squarely on the logistics involved to complete the distance. The women’s winner will typically complete the circuit in 30 hours.

“I think come race day there is no need to worry, you just have to get it done. Be flexible and go with whatever is happening,” she said. “At the moment, I am just stuck on getting all the race day food and equipment sorted in my mind.”

Kilian Jornet, defending champion and course record holder (22:42:33), of Catalonia, will return for this year’s race, and is highly favored. He beat the previous record by 40 minutes while taking pictures along the way.

It’s those stunning (and breathtaking) landscapes of the San Juan Mountains that thrill those who are lucky enough to earn a spot on the starting line.

 “I am more inspired by the terrain than I am moving through than I am by the competition at the moment, and Hardrock provides some of the most special and beautiful mountain running around,” Campbell said.

Frost, of New Zealand, who will be joined by three-time defending women’s champion, Darcy Piceu, has been in Silverton since June 5. Her preparations have already created a year’s worth of incredible miles and climbs. “I fell in love with [Hardrock’s] brutality, its beauty, the history of this area, and the people involved,” she said. “There is just so much to explore and see, every day is a treat.”