Inca Trail Marathon, Peru

Who: 50 runners

When: June 6, 2015 and August 1, 2015

Why it's unique: After whizzing past the hordes of tourists on 26.2 miles of the famed Inca Trail and ascending over 5,100 feet (with a peak of 13,800 at Dead Woman's Pass), you're welcomed by Machu Picchu, where you may recover among the ruins. If that's not enough, go for the Chasqi Challenge, which tacks on a run around Mount Ausengate and measures 100 miles in total. [andesadventures.com]