Well I only remember there is a little tower entrance like that somewhere in the castle area. But all I can recall is that it was on a cobbled type of path. I will guess at the guardroom of the castle.
There doesn't appear to be a cobbled type of pathway anywhere in the area in the photo, so I will bow to Macscouse's superior knowledge of this foreign land. Besides he's got the LHO to help him. She should know as she is a native.