Pfalzgrafenstein Castle (Burg Pfalzgrafenstein) is a toll castle located on Falkenau island in the Rhine River, near the bank close to Kaub. To ensure tolls were paid, chain booms were raised across the narrow river passage near the castle. If the toll was paid, the chain would be lowered and the ship could pass, or else the ship would be seized and the crew imprisoned in the castle dungeon.