Even if you're not all that fussed by industrial museums, this one's well worth checking out. At Llanberis much of the slate was carved out of the open mountainside – leaving behind a jagged, sculptural cliff-face that's fascinating if not quite beautiful. The museum occupies the Victorian workshops beside Llyn Padarn. It features video clips, a huge working water wheel, workers' cottages (each furnished in a progression from 1861 until 1969, when the quarries closed) and demonstrations.
The turn-off is along the A4086 between the Electric Mountain exhibition centre and the Snowdon Mountain Railway station.
