The eastern part of the Prealps between the rivers Isar and Inn is known as the Mangfall Mountains, because its streams - the Rottach, Weißach, Schlierach and Leitzach - all flow into the Mangfall river, which drains the whole area and forming an important groundwater store for the city of Munich. The highest peak in the eastern part of the Bavarian Prealps - located on Austrian state territory in spite of the name - is the Hinteres Sonnwendjoch at above sea level.