The Isar is a non-navigable river in Tyrol (Austria) and Bavaria (Germany) for vessels larger than raft size, which after a 292 km run south of Deggendorf joins the Danube from the right.
It rises in the Alps in the Tyrolean part of the Karwendel in the Hinterautal valley, changes after about 22 km below Scharnitz over the state border to Bavaria, where it still flows in the Alps, first through Mittenwald, then through Krün, Wallgau and in the so-called Isarwinkel through Lenggries and Gaißach flows.
It reaches the foothills of the Alps at the beginning of the middle reaches near Bad Tölz, followed by the towns of Geretsried, Wolfratshausen, Munich, Freising and Moosburg.
The lower course flows through Landshut, Dingolfing, Landau an der Isar and Plattling.
The Isar flows into the Danube five kilometers south of Deggendorf.
The former form as a typical mountain and foothills river with a wide, constantly shifting river bed, extensive gravel banks and branched river arms is only evident in individual areas of the upper reaches.
After the Danube, the Inn and the Main, the Isar with its catchment area of 8964.57 km², which is mostly in Bavaria, is the fourth largest river in this federal state.
The most important tributary is the Amper, which flows into Moosburg, followed by the Loisach, which flows into Wolfratshausen.
(Source: Wikipedia)