41 riders from 15 countries have entered August's Mongol Derby, known as "The Longest Horse Race on the Planet" and "the longest, toughest horse race in the world," across the wild and remote steppes of Mongolia.
Riders race 40 km at a time over 1000 km from urtuu to urtuu where they change horses, imitating Genghis Khan's postal system. The Monogolian horses are "semi-wild", and riders negotiate their routes by map and GPS.
Last year's Mongol Derby provided terrific drama:
http://www.endurance.net/international/Mongolia/2013MongolDerby/