The Rhine and some of its tributaries, such as the Main, Nahe and Neckar, are of eminent importance, especially in Germany, in terms of viticulture. This is because a large part of the German vineyards in 10 (of 13) directly bordering German wine-growing regions or in the immediate vicinity are located on the sometimes steep slopes of these rivers. The importance of the river is also underlined by the fact that the most important German grape variety, Riesling, is often named Rhine Riesling. The Rhine, like all bodies of water, has a positive effect on viticulture or creates the conditions for it by forming valley slopes. The river, which is 1,233 km long in total, 857 km of which are in Germany, is formed from two headwaters in the canton of Graubünden in the Swiss Alps. After the confluence of the Vorderrhein (77 km) and Hinterrhein (72 km) at the municipality of Tamins-Reichenau, it is called Alpenrhein and flows into Lake Con stance at the municipality of Hard. After passing through the Obersee, it is called Seerhein in the four km long section, flows through the Untersee and is now called Hochrhein after exiting at Stein am Rhein. Up to Basel, this forms the border between Switzerland in the south and Germany in the north.