Heidelberg is a city situated on the river Neckar in south-west Germany. The fifth-largest town in the State of Baden-Württemberg after Stuttgart, Karlsruhe, Mannheim and Freiburg im Breisgau, Heidelberg is part of the densely populated Rhine-Neckar Metropolitan Region. In 2015, over 156,000 people lived in the city.A former residence of the Electorate of the Palatinate, Heidelberg is the location of Heidelberg University, contemporary Germany's oldest and among its most reputable universities. Heidelberg is a popular tourist destination due to its romantic and picturesque cityscape, including Heidelberg Castle and the baroque style Old Town.GeographyHeidelberg is in the Rhine Rift Valley, on the left bank of the lower part of the Neckar in a steep valley in the Odenwald. It is bordered by the Königsstuhl (568 m) and the Gaisberg (375 m) mountains. The Neckar here flows in an east-west direction. On the right bank of the river, the Heiligenberg mountain rises to a height of 445 meters. The Neckar flows into the Rhine approximately 22 kilometres north-west in Mannheim. Villages incorporated during the 20th century stretch from the Neckar Valley along the Bergstraße, a road running through the Odenwald hills.