Trier (founded by the Romans - oldest town in Germany). Very fun to stroll the streets or peek into the cathedrals. I saw the robe of Jesus here in 2012. www.RiverCruiseGuru.com for free assistance with your river cruise.
Langen Foundation near Neuss, North Rhine-Westphalia, Germany is a museum designed by Japanese architect Tadao Ando. The foundation showcases a collection of Oriental Art and Modern Art. It is located on the grounds of the Museum Insel Hombroich.