Once the mightiest fortress on the Rhine, Burg Rheinfels was built in 1245 by Count Dieter V of Katzenelnbogen as a base for his toll-collecting operations. Its size and labyrinthine layout are astonishing. Kids (and adults) will love exploring the subterranean tunnels and galleries (bring a torch). To reach the sprawling ruins, it's a 20-minute uphill walk, or you can take the Burg Express Shuttle from St Goar's Marktplatz, or drive (parking €2). The complex incorporates a romantic hotel .
