The Elbe Tributary is a river system in Central Europe that flows into the North Sea. It is made up of four rivers: the Iser, Eger, Saale, and Ohre. The Iser is a river in the Czech Republic and Poland, the Eger is a river in the Czech Republic, the Saale is a river in Germany, and the Ohre is a river in Germany and the Czech Republic. All four rivers flow into the Elbe River, which then flows into the North Sea.