The Hardrock Hundred Endurance Run is a challenging ultramarathon held annually in the San Juan Mountains of Colorado. Covering a distance of 100.5 miles, the race features a significant elevation gain of over 33,000 feet, making it one of the toughest endurance events in the world. Runners navigate rugged terrain, high altitudes, and unpredictable weather conditions. Established in 1992, the race is known for its unique loop course that includes numerous mountain passes, some exceeding 13,000 feet. Participants must complete the run within a 48-hour time limit, and the event emphasizes self-sufficiency, requiring runners to carry essential gear.