The Dunav, also known as the Danube, is the second-longest river in Europe, flowing approximately 2,860 kilometers. It originates in the Black Forest of Germany and travels through ten countries, including Austria, Hungary, and Serbia, before emptying into the Black Sea. The river is an important waterway for trade and transportation. The Dunav is known for its diverse ecosystems and rich biodiversity, supporting various species of fish, birds, and plants. It also plays a significant role in the cultural and historical development of the regions it traverses, with many cities, such as Vienna and Budapest, located along its banks.