Heidelberg is situated on the banks of the river Neckar in Baden-Württemberg (in the region of Baden) and has nearly 150,000 inhabitants. ICE and EC trains arrive at and depart from the main station of the city. Together with is neighboring cities of Mannheim and Ludwigshafen am Rhein, Heidelberg builds a significant metropolis. The Heidelburg Castle sits above the lovely old town of Heidelberg. The Peterskirche is used as university church and at the same time it is the oldest Christian church in Heidelberg. Besides taking a walk through the old city of Heidelberg, participants of trade fairs can also take a boat tour on the Neckar to the Rhine. The former baths in Bergheim count among the best preserved art nouveau indoor pools. Today, they serve as market hall and as venue for various events.