Aberllefenni quarries

Aberllefenni quarry is the collective name of three slate quarries, Foel Grochan, Hen Gloddfa (also known as Hen Chwarel) and Ceunant Ddu, located in Cwm Hengae, just to the west of Aberllefenni, Gwynedd, North Wales. It was the longest continually operated slate mine in the world until its closure in 2003. Foel Grochan is the quarry on the north side of the valley, facing Ceunant Ddu and Hen Gloddfa on the south; all three were worked as a single concern throughout their history. Rock was mainly extracted underground, though all three quarries had open pits as well.