It's the tilted tower in Caer Lem.
I think it's the academic side quest since my character with that background got the quest. I cast fly (bought the scroll from the merchant) and you can fly to the tower and there is a section where it's glowing blue which I presume should lead to another map but when I get there, nothing happens.
When a character gets to the blue region on the tower they throw down a rope to let everyone else climb up, the rope itself is on the leftmost part of the ledge. As for how to get to the tower, as someone else mentioned, the merchant nearby sells a scroll o flying and a potion of flying too if I'm not mistaken, you could have a wizard cast "levitate" - rise up to the ledge and cast "misty step" to get on it. I haven't tested it yet, but perhaps "Spider Climb" would also do the trick?