There were two adjacent quarries in the Glynrhonwy area, north west of Llanberis, Gwynedd, Wales.
They were:
The quarries operated internal railways of 2 feet (610 mm) gauge and were served by Glynrhonwy Siding off the LNWR's Caernarfon to Llanberis branch.
Lower Glynrhonwy Quarry was acquired by the Air Ministry in 1939 for munitions storage. They occupied the site until 1961. During the Second World War the site generated two extra trains per day on some occasions. The railway siding was taken out of use on 18 December 1956.
A 100 MW pumped storage project received approval in 2017.
References
Glynrhonwy Quarries Wikipedia(Text) CC BY-SA