It was placed right across the path from the Fulton stone. If you put your back to the Fulton stone and cross the path, you'd trip over it.
The stone was about five inches deep, about a foot tall, and about 18 inches long... Just guestimations, but it wasn't nearly as large as some of the ones closer (like Deck) but it wasn't a tiny little thing either.
Ghost saw me standing in front of it, and he must have seen the odd expression on my face. I was trying to remember if I had ever seen it there, and I couldn't recall a stone with a cross on it before in there. He came next to me and was shocked to see the "new" stone.