The Karl Theodor Bridge, commonly known as the Old Bridge, is an arch bridge in Heidelberg that crosses the Neckar river. It connects the Old City with the eastern part of the Neuenheim district of the city on the opposite bank. The current bridge, made of Neckar sandstone and the ninth built on the site, was constructed in 1788 by Elector Charles Theodore, and is one of the best-known landmarks and tourist destinations in Heidelberg.