It's in the courtyard after you go through the outside entrance and before you actually enter the indoor "lobby". There are two of them, one to the right and one to the left as you stand in the courtyard. Here's a larger shot of the wall.
Yep- we are leaving next week so I am looking forward to it. I've been up there quite a few times but this will be the first time with a dslr so I can't wait.