The Orne gave birth to the relief at the origin of the name and reputation of Norman Switzerland. Leaving the soft sedimentary rocks of the Bassin Parisien to enter the Massif Armoricain, the river collided with the hard rocks of the Bocain syncline. It then traced its course in the Precambrian shales of the Massif Armoricain by drawing a series of irregular meanders. These meanders are dominated by large rocky escarpments of conglomerates and sandstone such as the rocks of Cambronnerie, Parcs and Houlle located near Clécy in the Calvados department.