Park in the large car park to your left, just after the entrance to the Rimbach. You'll no doubt be surprised by the number of cars when the weather is good.
Follow the small road that continues for a short kilometre. (1) It then turns into a stony path marked with yellow crosses, alongside a river and through forest. If you're worried about your ankles, take the path on your right just before the end of the road. It is marked by blue circles.
Continue on either of the paths until the Lac du Petit Neuweiher (2) which adjoins the Grand Neuweiher (3). This was emptied completed a few years ago (2007) in order to rebuild the embankment that retains the water. Geologists were worried that a fault passing underneath would break, causing a serious flood in the Doller valley. Following these works, the lac has lost a few metres in height.
Then reach the Auberge de Neuweiher (hostel) (4) and turn left on the GR531 marked by blue rectangles. You then climb a little and join the Chaume du Gresson and the Ferme-Auberge du Gresson Moyen at an altitude of 937m (5)