You must be prepared to do a lot of walking and stairs. Sometimes the ships are docked next to each other and you might have to walk up and down several flights of stairs to cross over the ships. There is a lot of walking on cobblestone streets so bring very good walking shoes!
Take advantage of all the onboard activities and excursions.
Be aware there are bikes on board that can be used in most every stop--there are wonderful bike paths all along the rivers. The crew did not make that clear. My husband looked into it because our prior ship had them and he used them many times. It really added to his enjoyment of the cruise!!