Bavaria is a country of high plateaus and medium-sized mountains. In the north are basalt knolls and high plateaus; in the northwest are the wooded sandstone hills of the Spessart. The northwest is drained by the Main River, which flows into the Rhine. To the southeast the topography varies from the stratified land formations of Swabia-Franconia to shell limestone and red marl, the hill country of the Franconian-Rednitz Basin, and the limestone mountains of the Franconian Jura along the Danube, which divides Bavaria north and south.