The region covers a large part of the Aquitaine Basin and a small portion of the Paris Basin (the border between the two being located at the Seuil du Poitou) and the Limousin plate (part of the Massif Central) and the western part of the Pyrenees. It is part of five watersheds facing the Atlantic Ocean: Loire, Charente, Garonne and Dordogne (and their extension, the Gironde estuary) and Adour, giving rivers bordering land dedicated mostly to viticulture and to agriculture.