The Arandar mine is located to the north of the exit from the pass in Tirannwn and to the east of Prifddinas' eastern wall. It is guarded by two dire wolves.
The mine is difficult to reach and rarely visited except for special purposes, such as the Regicide quest. Limestone is neither very profitable nor fast experience to mine, and Silvarea Mine is far easier to reach.
Starting from the entrance to the Underground Pass, north of Lletya, walk west past the pile of rubble. Go north through the dense forest. Take the log balance across the water and jump over the pitfall trap. The mining site is then to the north-east with no further obstacles.