Similar to the round trip trail on the right slope, there are also 10 tourist information boards on the left slope, but here the red dot trail has a longer route, different from the mere walk past the 10 boards. The first board is opposite the first one fixed on the right slope. Climb up near the second board, where there is a signpost, responsible for this route and also for trail 14 (blue cross). This is where you leave the thematic route and head toward Data massif, which rises to the north. Trail markers are slightly visible, but there is a signpost at the intersection of the trails. From this signpost, you start quite a difficult ascent to the top of Data massif, where the scenery is impressive. The ascent goes through a rocky area that is quite dangerous especially in wet weather and that is equipped with chains. A few meters before reaching the top, the trail goes round the peak - to the south, then enters the forest and descends to a meadow. Leave the ridge and turn right (east), start a steep descent through the forest and then through an area with shrubs, heading towards Data Saddle, where you come across trail 14 (blue cross). Continue to the south, walk past a small wooded peak and have a break in another saddle, where you find the fifth board of the thematic trail (because of the detour via Data peak, you "by-passed" the third and the fourth boards). Walk past the sixth board, where again the scenery is magnificent. Then climb to the highest point on the left slope and immediately after the peak reach the seventh board. Continue along the ridge, through the forest, to a saddle located just before a large cliff that seems difficult to pass. The eight tourist information board is here. Turn left (east) and descend more steeply through the oak forest, as indicated by the ninth board located at the edge of the forest. Walk through a pasture with shrubs that makes it a little difficult to follow the trail marking, but eventually reach DN107M national road, about 1.5 km downstream from where you started.