This race is a looped 100.5 miles of dirt trails along the San Juan Range of Southern Colorado (USA) with a total elevation of 67,984 feet.
Starting at 6am, the cut off time for the race is 48 hours.Runners cover extremely rugged terrain, steep scree climbs and descents, snow, river crossing and boulder fields.
Alternating between clockwise and anticlockwise every year, this extremely challenging course leads participants from Silverado through the towns of Telluride, Ouray and Sherman and back, crossing 13 major passes in the mountain range. Survival and navigational skills are required.