The Neckar is a 362-kilometre-long river in Germany, mainly flowing through the southwestern state of Baden-Württemberg, with a short section through Hesse. The Neckar is a major right tributary of the Rhine. Rising in the Schwarzwald-Baar-Kreis near Schwenningen in the Schwenninger Moos conservation area at a height of 706 m above s…The Neckar is a 362-kilometre-long river in Germany, mainly flowing through the southwestern state of Baden-Württemberg, with a short section through Hesse. The Neckar is a major right tributary of the Rhine. Rising in the Schwarzwald-Baar-Kreis near Schwenningen in the Schwenninger Moos conservation area at a height of 706 m above sea level, it passes through Rottweil, Rottenburg am Neckar, Kilchberg, Tübingen, Wernau, Nürtingen, Plochingen, Esslingen, Stuttgart, Ludwigsburg, Marbach, Heilbronn and Heidelberg, before discharging on average 145 m³/s of water into the Rhine at Mannheim, at 95 m above sea level, making the Neckar its 4th largest tributary, and the 10th largest river in Germany. Since 1968, the Neckar has been navigable for cargo ships via 27 locks for about 200 kilometres upstream from Mannheim to the river port of Plochingen, at the confluence with the Fils.