Julia Stewart of Washington, D.C., has competed in the 2016 Mongol Derby, a horse race that currently holds the Guinness World Record title of the longest multi-horse race in the world.

The Mongol Derby was founded in 2009 by a UK-based group called "The Adventurists". The course is 1,000 kilometers, or 621.37 miles, long, and recreates the horse messenger system developed by Genghis Khan in 1224 through the Mongolian-Manchurian steppe, a temperate grassland zone. The exact course changes every year and the is unmarked. Riders are given a series of GPS coordinates to guide them to each horse station – certainly an improvement which Genghis Khan would have approved. They have 10 days to complete the race.

Riders switch horses approximately every 40 kilometers. The horses, which belong to families who live along the course, are semi-wild.