Hardrock Hundred Mile Endurance Run

The Hardrock Hundred Mile Endurance Run is an ultramarathon 102.5 miles (165.0 km) in length, with 33,000 feet (10,000 m) of climb at an average elevation of over 11,000 feet (3,400 m). The race is held on a loop course on 4WD roads, dirt trails, and cross country in Southern Colorado's San Juan Range, US. The race is dedicated to the memory of the miners who settled in the area and who built the mining trails on which much of the race is run.

Source: Wikipedia — Hardrock Hundred Mile Endurance Run (CC BY-SA 4.0)