This place isn't normally accessible by anyone, and not because of the castle's trickery- this is a secluded place on top of one of the castle's many roofs, a favorite place for the Maester to sit and watch various goings-on, or just sit and contemplate. It's a good spot because you can easily get to other roofs from there, and see down into various spots in the Castle, to observe unwitting people. It also provides a great view of Asgard Academy~