Wisła or Vistula, longest river of Poland, and one of the major rivers of eastern Europe, with a length of 1,090 km (675 mi). It rises on the northern slope of the Carpathian Mountains in southwestern Poland and, flowing north, curves to the east, then to the west. Before entering the Gulf of Gdańsk (formerly Gulf of Danzig, an arm of the Baltic Sea), the river splits into two main channels. Among the principal tributaries are the San, Narew, Bug, and Brda rivers. The Wisła is navigable for almost its entire length by small craft and is linked by canal to the Odra (Oder) River system. Major cities on its course include Kraków, Warsaw, and Toruń; the port of Gdańsk lies to the west of its mouth.