The ruins are found in the north-west part of Keldagrim, north of the library. To get there, take the train from the Grand Exchange in Varrock all the way to Keldagrim. Run north until you see the bridge to western Keldagrim. Cross the bridge, run west and the entrance to the cave will be on the northern wall; the cave contains the ancient ruins. The mining experience is as follows (note that each statue can only be mined for experience once):