Backyard Cycling Ultra is a last-rider-standing cycling race in Weert, Bornem, Belgium, with one rule: ride 24 kilometers every hour or drop out. Only 100 riders start, and each new round begins at the top of the hour with the whole group rolling out again.
Finish the loop inside 60 minutes and you get whatever time is left to eat, drink, recover, and get ready; miss the cutoff and your race is over. There is no set finish distance, because the event ends only when one rider is still able to start and complete another round.