That's kind of the beauty of it to me, Lowell. Once you're on the ship, you can make decisions day by day on the walking tours. There were several couples that one might go on a certain tour and the other would stay on the ship. There was one man who only left the ship for one tour......the rest of the time he stayed aboard and ate and drank. His wife didn't miss a thing, she just went without him and buddied up with other passengers.  I don't think any of the guided parts of any tours were as long as a mile, with the possible exception of Strasbourg France. And I would go back there again if I had to crawl to do it. On every tour you have a headset device so you don't have to stay within 4 ft of your guide to know what's going on. You're bussed from the river dock to the start point of each tour and then bussed back at the end. The only tour we did that is absolutely not for the faint of heart was up to Marksburg Castle. Email me if you want any other info.......I could type all morning about the wonders of that trip! :~)