Task: Text Categorization
Input (English): A journey down this river is the subject of Between the Woods and the Water by Patrick Leigh Fermor. Before flooding due to a hydroelectric project, this river's small island of Ada Kaleh was home to a large Turkish population. In 2000, tributaries of this river were affected by a huge cyanide spill from a gold mine near Baia Mare. This river is home to Europe's largest binational hydroelectric dam at the Iron Gate. A major canal links this river to the Main. The Regen flows into this river at Regensburg, and its other tributaries include the Sava and the Tisza. Before the construction of the Szechenyi Chain Bridge, this river divided the twin cities of Buda and Pest. For 10 points, name this river that flows past Belgrade and Vienna and empties into the Black Sea.
Output (English): Social Science