Is there a way to do this? It could not be obvious, and it would be especially cool if it were a matter of doing something funky with a keystone, or something, that would make it topple (or possible to crawl though it) if something was removed at one or two points.
The wall is mine to 'build' - so if there is some certain kind of wall where this would work, I could write that kind of wall.
But the sad truth is that I know nothing of masonry, and have built no walls, real or imagined. Have you?