Sounds awfully trite, I know, but I'm sure it is just because it's to do with archaeology - they don't just want a "Mauer", even if that's all it is...

Have a look here:

http://images.google.de/imgres?imgurl=http://www.aegyptologi...

or alternatively google "Mauerzug" in google images, and select the second one in at the top.

You really don't need "course of the wall" in your case, 'cos they immediately tell you it's circular in shape...