The eye-level slots cannot be opened.
Looking through the ground-level one, Neldor can see another door just like the one you're crouching by. You can see that a very complex locking mechanism is holding the door shut, and you can see a symbol carved very intricately and precisely into the door. It is a set of calipers, and it looks very much like this:
http://3.bp.blogspot.com/_TqCjVEcSXY...+calipers..jpg
Make Knowledge Religion checks, please