Comrades Marathon (South Africa)

Comrades Marathon is the world's oldest ultramarathon, with 87 kilometers alternating between 'up' and 'down' runs from Durban to Pietermaritzburg. Its notorious 12-hour cutoff crushes over 20% of starters annually—stricter than UTMB's (#5) 48-hour limit, yet the DNF rate is four times higher than Tokyo Marathon's (#6) mere 2%. With 25,000 finishers yearly, it is five times larger than the average trail ultra. Elevation gain hits 1,600 meters in the 'up' run, while the 'down' run averages 50% faster splits, creating a unique challenge that surpasses Tokyo Marathon's flat course in both distance and cutthroat timing.