Southern Germany's landforms are defined by various linear hill and mountain ranges like the two adjacent ranges of the Swabian and Franconian Alb (reaching approximately from the source of the Danube in the southwest of Baden-Württemberg, south of Stuttgart, across Swabia into Central Franconia and to the valley of the river Main) and the Bavarian Forest along the border between Bavaria and the Czech Republic. The Alps on the southern border are the highest mountains, but relatively little Alpine terrain lies within Germany (in southeastern Swabia and Upper Bavaria) compared to Switzerland and Austria. The Black Forest, on the southwestern border with France, separates the Rhine from the headwaters of the Danube on its eastern slopes.