It unites by going around 2 or more countries. For example; It unites Czech Republic and Slovakia. It divides by going through the country Hungary for example.
The Most important river for Eastern Europes transportation is the Danube River.
The Danube river is located on the continent of Europe, particularly in Central and Eastern Europe. It is the second longest river in the continent.
Danube
Danube River and Volga River.
the volga is the longest river of one name entirely within eastern Europe tho the combined ob irtysh is longer but partly outside Europe so it depends on what you will accept
The River Danube is located in Central and Eastern Europe. So it is in the European continent.
The Danube River.
The Danube River.
The Danube River is located in Europe.
Balkan peninsula
The Danube River is on the continent of Europe.
The Danube River.