The Horizontes Backyard Ultra is an official race on the Backyard Ultra calendar. An American concept created by Lazarus Lake, organizer of the famous and legendary Barkley Marathons in the Frozen Head Nature Park in Tennessee.

The logic of this race is very simple: complete a loop of 6,706 km in a maximum time of 1 hour. Every hour there is a start and everyone has to complete the Loop in under an hour. If someone finishes earlier, they can rest while waiting for the new Loop to start.