Thomas, you are so right, I have sailed the Main to Frankfurt and a little bit of the Neckar. I liked Mainz especially the Gothenburg Museum, where I got told off for photographing some of the books!
Jacques you are also right of course. I am always amazed at the quality of the masonry crafted by our ancestors with only basic hand tools and block & tackle.
I wonder if the same quality of workmanship is available in this day and age?c