Yeah it's mostly North-African and French athletes doing this one. 240 km in 6 days, carrying your own food. I don't know any race tougher than this one. An ironman is a piece of cake compared to this.
well its up there, some argue the barkley is tougher, its actually a rogaine, , only 13 runners have every completed the 100 mile course inside the 60 hour cutoff. approaching 20,000m of climbing.... http://www.mattmahoney.net/barkley/