Saskatchewan contains two major natural regions: the Boreal Forest in the north and the Prairies in the south. They are separated by an aspen parkland transition zone near the North Saskatchewan River on the western side of the province, and near to south of the Saskatchewan River on the eastern side. Northern Saskatchewan is mostly covered by forest except for the Lake Athabasca Sand Dunes, the largest active sand dunes in the world north of 58°, and adjacent to the southern shore of Lake Athabasca. Southern Saskatchewan contains another area with sand dunes known as the Great Sand Hills covering over . The Cypress Hills, located in the southwestern corner of Saskatchewan and Killdeer Badlands (Grasslands National Park), are areas of the province that were unglaciated during the last glaciation period, the Wisconsin glaciation.