Station As - purple - 10,1 km

Until 2017, gravel was extracted north and south of the Kolenspoor. After that, the area was restructured in a landscape-friendly way by the Restructuring Committee (now the Gravel Committee) before being returned to nature. The area is named after the nearby erratic boulder that marks the border between the former municipalities of Lanklaar, Niel-bij-As, and Mechelen-aan-de-Maas.

Between the area 'Aan de Windelsteen' and the Rouwmortelven lies Bosheide, which has truly earned its name. You will find open heathland, heathland with tree regrowth, and fully wooded heathland. An ideal habitat for the tree lark, tree pipit, and butterflies such as the purple hairstreak. Cross-leaved heath also occurs here. This is an endangered plant in Flanders and finds its most important growing place here in the Nationaal Park Hoge Kempen.

You also pass by the Rouwmortelven. This beautiful heathland pond is a chosen spot for plants of the "wet heathland": cotton grass, cross-leaved heath, and the carnivorous sundew. It is a habitat for dragonflies and amphibians, including a number of very rare species (moor frog, great crested newt, white-faced darter).