We spent half a day exploring Rheinfels Ruine before heading back to Frankfurt. Rheinfels Ruine is famous for being the most impenetrable castle on the Rhine. Built in the 13th century, it successlly repelled all invasions until 1794 when a cowardly general handed over the castle to French revolutionaries without a fight. The French victors blew the castle to pieces. At the top of the castle, you can see Burg Katz to your right and Burg Maus in the distance to your left :)