From the other side? How do you do that?
I know the other one leads to the apprentice, but that's a dead end, isn't it?
That one, yes. But if you go to the east there's another door, also with a hidden switch, that leads outside into the realm of the ice king Boreas.
The door in that picture is opened either by backtracking from his castle, or by jumping\teleporting from a certain point on several stone heights along the castle wall.
