Kaub is a town along the Rhine river known for its medieval castle ruins. The town contains well-preserved walls and towers from its historic fortifications. Nearby is the island fortress of Pfalzgrafenstein Castle, built in the 14th century to collect tolls from passing ships. It can only be reached by ferry and gives visitors a sense of what life was like in the Middle Ages without modern amenities. The water levels at Kaub are also an important indicator for navigation on the Rhine.