Finishing a marathon is the ultimate achievement for most runners. But for a group of unique athletes—ultramarathoners—26.2 miles isn’t enough. They train for years in order to test the limits of their legs over 50, or even 100, miles of mountainous terrain. (To put that into perspective, if you start in Denver and run north, you’d be in Wyoming before you cover 100 miles.) Thanks to our many mountains and active culture, Colorado has become the unofficial home of ultrarunning and hosts some of the most exciting and feared races of the season.

For the majority of us, these kinds of feats are out of the question. But as a spectator, ultramarathons inspire a sense of community, excitement, and awe like almost nothing else. Grab a few water bottles and snacks, and head to one of the many thrilling races coming to Colorado this summer.

San Juan Solstice

Looks can be deceiving. While only half the distance of the longest ultramarathons, the 50-mile San Juan Solstice carries a ferocious reputation. The trails weave through the San Juan Mountains, hovering between 8,500 and 13,000 feet of elevation. Paired with spectacular alpine views, many describe this course as a mini Hardrock (see below).

When: 5 a.m., June 21

Where: Lake City, a five-hour drive from Denver

Hardrock 100

With more than 67,000 feet of elevation change, this annual 100-mile race in Silverton is considered one of the most grueling ultramarathons on the planet. Only 140 hyper-experienced ultraracers are allowed to participate each year. On average, a little more than half of them will finish.

When: 6 a.m., July 11

Where: Silverton, about a six-and-a-half hour drive from Denver

Grand Mesa Ultra Marathon

This trio of races (60K, 50 miles, and 100 miles) at Grand Mesa in West Colorado is a popular newcomer to the ultra scene. Participants in all three races begin at the same time, boosting the sense of community.

When: 5 a.m., July 26

Where: Grand Mesa, just outside of Cedaredge, and about a five-hour drive west of Denver

Telluride Mountain Run

Does the thought of just watching someone run 100 miles tire you? Perhaps you’d prefer cheering runners through the 38-mile long Telluride Mountain Run through the San Juan Mountains. Celebrating its second anniversary this summer, the race prides itself on attracting tough runners who need little aid.

When: 6 a.m., August 9

Where: Telluride, a six-hour drive or one-hour flight

Leadville Trail 100 Run

As one of the most prestigious ultras in the world, this 100-mile race attracts runners, sponsors, and spectators from around the globe. Beginning in Leadville, the highest city in the United States, it winds its way through trails forged by 20th-century miners.

When: 4 a.m., August 16

Where: Leadville

The Grand Traverse

For 17 years, cross-country skiers around the world have made the pilgrimage to Crested Butte for the storied Grand Traverse, a 40-mile winter race that ends at the base of Aspen Mountain. This year, for the first time ever, the same race will take place during the summer on feet instead of skis.

When: 6:30 a.m., August 16

Where: Crested Butte, a four-hour drive

Run Rabbit Run

This late season double-header (50 miles and 100 miles) promises cooler temperatures and beautiful fall colors. The race is sure to be on the minds of many ultrarunners, as the winner gets a sizeable chunk of prize money. Any spectator who guesses the correct winner will find themselves $250 richer as well.

When: The 100-mile race is September 12 at 6 a.m.; the 50-mile race is September 13 at 8 a.m.

Where: Colorado Springs

Ultra Race of Champions

With a name like Ultra Race of Champions, this series of races (half marathon, 50 miles, 100 miles) at Copper Mountain is bound to draw some of the sport’s biggest names.

When: September 16

Where: Copper Mountain, less than two hours west of Denver

—Image courtesy of Shutterstock