Elbe (ĕlˈbə) [key], Czech Labe, a major river of central Europe, c.725 mi (1,170 km) long, rising in the Krknoše Mts., NW Czech Republic, and traversing NW Czech Republic in a wide arc. It then cuts through steep sandstone cliffs, enters E Germany, and flows generally NW through E Germany (past Dresden, Wittenberg, and Magdeburg) and onto the North German plain. The Elbe forms part of what was the East German–West German border before flowing across N central Germany (past Hamburg) and into the North Sea at Cuxhaven. In Hamburg, the river divides into two arms before forming a 60-mi-long (97-km) estuary. The chief tributaries of the Elbe are the Vltava, Mulde, Saale, and Havel rivers. One of the chief waterways of Europe, the Elbe is navigable for c.525 mi (845 km); freight-laden barges can move on the river as far as Prague. A canal system connects the Elbe with Berlin and the Oder River (to the east); with the Ruhr region and the Weser and Rhine rivers (to the west); and with the Baltic Sea (to the north). There are numerous dams in the Elbe River basin. Known as the Albis to the Romans, the river marked the farthest Roman advance into Germany (9 B.C.) and was later the eastern limit of Charlemagne's conquests. The Treaty of Versailles (1919) internationalized its course from the Vltava River to the sea, but Germany repudiated its internationalization after the Munich Pact (1938). In 1945 the river was made part of the demarcation line between East and West Germany.