Heidelberg German pronunciation: [ˈhaɪdəlbɛʁk] is a ceety in sooth-wast Germany. The fift-lairgest ceety in the State o Baden-Württemberg efter Stuttgart, Mannheim, Karlsruhe an Freiburg im Breisgau, Heidelberg is pairt o the densely populatit Rhine-Neckar Metropolitan Region. In 2011, ower 149,000 fowk lived in the ceety. Heidelberg lies on the River Neckar in a steep valley in the Odenwald.