With its 105 miles (170 km), the Orne is the second largest river in Normandy after the Seine. It weaves its way between the cliffs and the forests of Norman Switzerland. The region is the meeting point of hard rocks belonging to the Massif Armoricain and softer rocks of the Bassin Parisien. The river dug its bed in the latter, leaving high shale cliffs on either side. Kayak trips are possible for about 17 miles (28 km) in a site listed as Natura 2000 for its biodiversity.