Covered 27.3 km (17 mi) to reach the Rhein River, cross it on a foot bridge tacked on next to a rail bridge, and walk a bit further to a modern youth hostel at the edge of the Mainz Volkspark (People's Park). The Main River that I've been following the past two days enters the Rhein just 200 m down stream of the bridge (see pic).
A few other things that particularly impressed me are: (1) walking under the Rhein-Main Airport landing flight path, (2) seeing my first Bike and Ride, (3) walking by a huge 2-D bar code, and (4) walking through the city of Rüsselsheim, home of the Opel car, a wholly owned GM subsidiary. But more, their lot was filled with a majority of Opels--is that brand loyalty or employer loyalty, or just a good deal??!