|This article is about location in The Witcher 3. For the similarly named Druids' circle, see Caed Dhu.|
Kaer Dhu is a ruined fortress located east of and across the lake from Fornhala. Some Griffin School gear is hidden within Kaer Dhu. The nearby forest is infested with nekkers and a high-level werewolf also prowls the surroundings.
Within Kaer Dhu is the entrance to inside the fortress, containing a nekker warrior and several nekkers. This connects to a cave and then a mine, finally emerging on the other side of the mountain.