Starting from the centre of Chamonix (1035m) the route climbs steadily towards the upper valley, progressively passing through the hamlets of "les Bois" and Lavancher to reach Argentière (1250m).
In Argentière the Marathon follows a trail towards Le Planet, from here you traverse across the fields to begin the trail on the Balcon Nord before going down towards Montroc.
After going through the village of Montroc you take the trail towards Tré le Champ and from here you go toward the Col des Montets.
The route crosses the "Col des Montets" (1461m) in the heart of the Aiguilles Rouges Nature Reserve. Then along the "chemin des Diligences", the old stage-coach route, you arrive at the hamlet of Buet before reaching Vallorcine (1260 m), nestled at the bottom of a pretty valley only a stone's throw from Switzerland.
Here begins the progression to the Col des Possettes (1997m) via a trail leaving from the Plan de l'envers.
A refreshment post is available a the top of the col before finally climbing up to the Aiguilles des Possettes (2201m) where you will be rewarded by a breathtaking panoroma of the Mont Blanc range.
Facing the ‘Aiguille Verte' and the Mont Blanc range, the route follows the ridgeline of the 'aiguillette' gradually descending in the direction of Tré le Champ.
You will go along a pretty trail that brings your toward le Tour, crosses through the village, and then takes you toward the Tour glacier. You will then take a north facing trail (a cooler perspective....)towards Montroc before crossing through the hamlets of the Frasserands and Tré le Champ.
At the heart of the Aiguilles Rouges massif, opposite the Mont-Blanc range, the route climbs up towards la Flégère (1875 m).
After crossing the magnificent Charlanon comb(1812m) the climb is gentle at first.
The gradient increases until just before the arrival at Planpraz (2050 m) giving one of the most beautiful views of the Mont-Blanc.
