Which major river touches 10 European plains?

The Danube River touches 10 European countries as it flows through various plains, including those in Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova, and Ukraine. It is the second-longest river in Europe and plays a significant role in the geography, economy, and culture of the regions it traverses. The river's basin supports diverse ecosystems and is vital for transportation and trade in the continent.