The main river that flows through central Europe, connecting multiple capitals, is the Danube River. Spanning approximately 2,860 kilometers, the Danube is the second-longest river in Europe, flowing through several countries, including Germany, Austria, Hungary, and Romania. It has been historically significant for trade and cultural exchange, linking cities like Vienna, Budapest, and Belgrade. The Danube is also vital for biodiversity, with many wetlands and natural habitats along its course, contributing to the ecological richness of the region.