A four-day mountain-bike race across the wilds of Costa Rica. Nearly 250 miles long, and with over 45,000 feet of climbing, the course often leaves riders stuck in thick jungle mud. Passing through a national park and over the slope of a volcano, La Ruta is billed as the most difficult mountain bike competition in the world.
Top 10 Endurance Competitions
This year's 24 Hours of Le Mans saw automaker Audi finish in first, second, and third place. TIME looks at other notable tests of human stamina.