City (pop., 2002 est.: 141,509), southwestern Germany, situated on the Neckar River. First mentioned in historical record in 1196, it was the capital of the Rhenish Palatinate and the residence of the electoral counts palatine until 1720. It was a centre of German Calvinism in the 16th century. Heidelberg was devastated during the Thirty Years' War (1622) and by the French in 1689 and 1693. It is the site of the 13th-century Heidelberg Castle, a major tourist attraction, and of the University of Heidelberg (1386), the oldest university in Germany.