The route is designed so that the total amount of climbing on the longest course exactly equals the height of nearby Mont Blanc, the highest mountain in the Alps and for which the event is named. To complete this long course participants have to have reached control points before certain cut-off times, otherwise they are re-directed on to the shorter versions of the route. This is possible because the routes of the three courses share the same initial and final sections, but the longer routes also incorporate various additional detours on the Col des Saises.