Everest Marathon, Nepal

Who: 75 non-Nepalese, 20 Nepalese runners

When: November, 2015

Why it's unique: While it's not the only race taking place in the shadow of Everest, this UK-based marathon stands out because it raises money for charities that benefit the people in rural Nepal. With a starting line at Gorak Shep, just below Everest base camp at 17,500, it's mostly downhill and passes though a varied landscape of boulders, grass, scree, and stone staircases; tough on your knees but because the path is unmarked, the real challenge, aside from breathing, is translating the map to terrain. [everestmarathon.org.uk]