Guidebook with maps/step-by-step :
1/ From the parking of the Granges ski lift, go up in the mountain pasture following the ski lift.
Reach a track, take it on the left and continue to climb towards the Bel Air wood.

2/ After 4 bends, leave the track and turn left on the path that will enter the Bel Air wood.
Staying on this winding path, cross the wood and come out on a vast space above the cable car station and a restaurant (altitude 2050m).

3/ Go south in the valley, pass under the Signal chairlift, stay below the rocky outcrop on the left and reach the edge of an artificial reservoir.

4/ Go past the reservoir on the right and continue to climb in a direction roughly parallel to the Pyramide ski lift.

5/ Pass the col de la Platta, reach the Parc de la Vanoise (large green line on IGN).

6/ Leave the path on the left that goes down to the Refuge du Grand Plan and continue on the balcony path (clear view on the Vanoise massif).

7/ Go down towards the Merlet Lakes Refuge and then the lower Merlet Lake.

8/ Go past the lake then start a small ascent on the right towards the upper Merlet Lake. Ideal for a break.