Aachen

Aachen needs 1 day: the cathedral, with the octagonal Palatine Chapel where Charlemagne is buried and where 30 German kings were crowned, is almost the sole focus of the visit. April-October is best. It's mid-priced by German standards. It was the capital of the Carolingian Empire under Charlemagne, and in 1978 its cathedral became the first German site to be named a UNESCO World Heritage Site, on the very first list of sites recognized worldwide.