This Saturday, the Audi Power of Four Ski Mountaineering Race returns to test winter endurance athletes to the max. The Power of Four is the winter edition of the annual endurance race series. The event tests athlete’s stamina as they race in teams of two across all four mountains making up the Aspen Snowmass resort. The grueling course covers 24 miles and more than 10,000 vertical feet of climbs. Starting in Snowmass Village, the teams traverse to West Buttermilk, then on to Aspen Highlands where they ski over to Aspen Mountain and end at the gondola plaza, at the base of Aspen Mountain. Sound like fun?