Pfalzgrafenstein Castle, island castle in the Rhine, UNESCO World Heritage Site, Upper Middle Rhine Valley, Kaub, Rhineland-Palatinate, Germany Pfalzgrafenstein Castle, island castle in the Rhine, UNESCO World Heritage Site, Upper Middle Rhine Valley, Kaub, Rhineland-Palatinate, Germany Pfalzgrafenstein Castle, island castle in the Rhine, UNESCO World Heritage Site, Upper Middle Rhine Valley, Kaub, Rhineland-Palatinate, Germany Pfalzgrafenstein Castle, island castle in the Rhine, UNESCO World Heritage Site, Upper Middle Rhine Valley, Kaub, Rhineland-Palatinate, Germany