Hi Any,
You are quite right, most of the quarry has disappeared beneath rubbish infill, however, the quarry built two relatively long tramways to waste tips, one to the west and one to the north. Some sections of the west tip tramway trackbed still exist and are worth seeking out, but the tramway to the north tip was an altogether more spectacular construction, consisting of a steeply graded reverse curve line built mostly on embankments. The Hunslet loco "Lilla", now resident on the Festiniog railway, was built specially for this railway. The embanked horseshoe curved sections still exists adjacent to the village of Y Fron and along with the Alexandria Quarry line, represents one of the more spectacular "mountain" railways in North Wales. A good view of the mountains behind Dublin from the tip as well. A "must see" loation in my opinion.
Cheers
Alan