(S) Depart from the Refuge de Terre Rouge in the commune of Valmeinier. Cross the Ruisseau des Grandes Culées, continue along the hillside, leaving the Chapelle Notre-Dame des Neiges on your left, and go to the Bissorte water intake. Continue to the junction about 150 m further on.
(1) Take the path on the right towards the Col des Marches. Climb up the valley, then reach the scree slopes where you will need to follow the cairns before arriving at the Lac de Roche Noire.
(2) Follow the signposted path north towards Col des Marches. You will find a well-marked path for a final steep climb to Col des Marches (altitude 2725 m).
(3) Cross the pass from west to east and descend into the Bissorte valley.
(4) Pass by a small lake and continue downhill towards the Refuge des Marches.
(5) At the fork below the refuge, ignore the footbridge and turn left towards Lac de Bissorte. Walk along the western shore of the lake until you reach the dam.
(6) Take the track that starts directly below the dam on the left bank and pass under the buildings above the dam.
(7) Leave the track and take the first path on the left before you reach the large building below the dam. Join the pretty Fenêtre du Prec path. Follow this path, which is a little dizzying but never difficult: take care with children or in wet weather. Continue straight down to reach the Prec car park (E).