This is actually at 31.1S 13.2W
The best way to find it is head East from Thorenhad until you reach 31.1s, 13.8w, which is the base of the hill and the path going up. Just follow the path counter-clockwise going up and step inside the arches to get the confirmation. You dont even have to go in far enough to get agroe, but if you do the Stone-Troll Flesheaters are 5k+ but there are 2 right at the entrance and one on the left going in so be careful.