Which of these German cities is not on the River Rhine?

The Rhine is one of the major European rivers. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps. It forms part of the Swiss-Liechtenstein, Swiss-Austrian, and Swiss-German borders. After that the Rhine defines much of the Franco-German border, after which it flows in a mostly northerly direction through the German Rhineland. Finally in Germany, the Rhine turns into a predominantly westerly direction and flows into the Netherlands where it eventually empties into the North Sea.

The various castles and defenses built along it attest to its prominence as a waterway in the Holy Roman Empire. Among the largest and most important cities on the Rhine are Cologne, Rotterdam, Düsseldorf, Duisburg, Strasbourg, Arnhem, and Basel. The city of Hamburg is not on the Rhine.

At the southern tip of the Jutland Peninsula, Hamburg stands on the branching River Elbe at the head of a 110 km (68 mi) estuary down to the North Sea, on the mouth of the Alster and Bille. Hamburg is one of Germany's three city-states alongside Berlin and Bremen, and is surrounded by Schleswig-Holstein to the north and Lower Saxony to the south.