The Danube River flows through central and eastern Europe for 2,857 km from the Black Forest in Germany to the Black Sea. It has historically served as a defensive barrier, transportation route, and cultural connection between countries. The Danube is referenced in many classical music pieces, stories, books, and films and plays an important role in Greek and Celtic mythology as the river was thought to flow from the land of eternal springtime inhabited by the Hyperboreans and was associated with the Celtic mother goddess Danu.