The Isar River originates in the Austrian Tyrol then in Germany is located entirely in the state of Bavaria with Munich the capital and most populated and cosmopolitan location on its banks with Freising the second largest city. The Isar is a north flowing tributary to the Danube River, which originates in Germany with its most significant cities being Ulm, Regensburg, Ingolstadt and Passau. The Isar is not navigable by watercraft larger than a raft so it is primarily used for water recreation and also as a source of hydroelectric power.

The Neckar, located entirely in Baden Wurttemberg, the state directly west of Bavaria, is a north then west flowing tributary to the Rhine, with Stuttgart, Heidelberg and Mannheim (on the confluence of the Neckar and Rhine) being the most notable cities on its banks.

The Limmat is entirely in Switzerland, merely a tributary to the Aare River, in turn a tributary to the Rhine, but boasts Zurich as its most important port of call.

More Info: en.wikipedia.org