This park lies in a limestone massif, in a bend in the Lesse. The river has hewn out an underground course here and this has been explored since 1962. The natural fortress site was occupied until the 10C, as shown by the reconstructed Roman baths and the ruins on top of the plateau, from where there is a fine view over the Lesse Valley. The headland is dotted with caves in which traces of prehistoric life have been found.