@BobCatter - I understand about the activity level being fine for some - but the issue with some is that even tho the description says "walking" tour people don't realize it could be anywhere from 2-5 miles of walking - and because it's largely on cobblestones in these old cities that's just so much different from walking on nice pavement here in the US.
@Azulamm - the included _____ by foot tours like I said above can be strenuous like the ones in Copenhagen and Karlskrona - whereas the included tours in Mariehamm and Ronne were almost totally on the buses. Berlin was a 2.5 hour train ride, then about a 1-1.5 hour bus tour with getting off at the Brandenburg Gate and riding past Checkpoint Charlie and a couple other highlights, then having about 4 hours to explore on your own and get back to your bus, then 2.5 hours back to the ship via train. Hope that helps