I stopped once while in the Cotswolds to watch 2 workmen repair an old wall. I talked to them for about an hour, watching how they selected stone for just the right purpose, and the wall just grew right before my eyes. There is really guite a lot of engineering that goes in to a well made drystone wall. In Cumbria and the surrounding borders area of Scotland, it is also amazing to see walls that go nowhere, not enclosing anything. I have heard that lots of these walls were just an effort to clear the fields of stone. I also have started taking photos of all the various stiles and steps and other means of crossing walls. Probably our UK friends think we North Americans are right daft to be so intrigued by something so commonplace to many of them