This walk takes you up and down a remarkable "cliff" with some geographical exaggeration.

On the western side of the Maas valley, a steep edge forms, an abrupt transition of about 45 meters in height, which extends over more than 20 kilometers from Opoeteren to Gellik. This is one of the most spectacular geological phenomena in the otherwise flat Flanders.

About 600,000 years ago, the ice ages began, during which the Maas, as a wide, meandering river, transported enormous amounts of gravel and debris from the Ardennes and other mountain ranges. This material was deposited in a fan-shaped cone of debris, the current Kempen Plateau, which rose higher than the surrounding areas. Due to the alternation of cold and warm periods, the course and strength of the Maas changed regularly. Sometimes the river deposited new debris, and sometimes it cut into its own deposits, creating a stepped terrace landscape. The steep edge marks the abrupt transition between the main terrace (the plateau) and the lower Maas valley (the middle and lower terraces). This height difference averages about 45 meters and is even 50 meters in some places.

The steep edge lies precisely at the transition between the Kempen Plateau and the Maas valley because here the plateau abruptly ends and the valley carved by the Maas begins. The plateau consists of relatively hard layers of gravel that withstood weathering and erosion better, while the Maas could cut deeper into the softer underlying sandy layers. This created a clear, steep transition in the landscape.