Great weather again. Temps in the high-70s and bright sun. The boat docks at Koblenz, a name which derives from 'confluence' because here the Main River flows into the Rhine.
Buses take us up to Marksburg castle, the only German castle never successfully attacked. As a result, it is in pristine condition. "Pristine", in this case, means it looks and feels like something out of the Middle Ages. There are few, if any, alterations beyond basic creature comforts like toilets. I'd show you images, but I've already spent nearly an hour unsuccessfully trying to upload two using Viking's 'free Wi-fi'. You'll just have to take my word for it.