The Czechoslovakian River is composed of four rivers: the Elbe, Iser, Eger, and Vltava. The Elbe is a river in Central Europe that flows from the Czech Republic to the North Sea. The Iser is a tributary of the Elbe that rises in the Krkonoše Mountains in the Czech Republic. The Eger is a tributary of the Elbe that rises in the Ore Mountains in the Czech Republic. The Vltava is the longest and most important river in the Czech Republic, flowing through Prague before joining the Elbe.