High above Porthmadog, in the empty upland between Cwm Pennant and Cwmystradllyn, two abandoned slate quarries sit like ruined castles on the hillside. Gorseddau and the Prince of Wales quarry are part of the Slate Landscape of Northwest Wales, which UNESCO listed in 2021, and they tell a story of big hopes and quick failure. Gorseddau in particular was developed in the 1850s with money and ambition, a tramway and a grand multi-storey mill at Ynys-y-Pandy whose roofless stone shell still looks like an abbey. The slate turned out to be poor, and within a couple of decades the whole enterprise had wound down.
What you find now are terraced galleries cut into the mountain, spoil heaps of blue-grey waste spilling down the slopes, the trackbeds of old tramways contouring across the hills and the remains of barracks where quarrymen lodged through the week. Sheep graze among it all. On a still day the only sounds are skylarks and the wind in the grass, and the reservoir of Llyn Cwmystradllyn lies dark below, backed by the bulk of Moel Hebog.
Getting there is half the fun. Narrow single-track lanes leave the A487 and A497 and wind up into the hills through gates and over cattle grids, with grass growing down the middle and walls close on both sides. They are slow, beautiful and demanding: blind bends, sudden steep pitches, loose stones and the occasional tractor coming the other way. Pull in where you can and let walkers' cars pass. The last stretch to the quarries themselves is on foot, so park considerately at the reservoir end.
Porthmadog, the nearest town, grew as the harbour from which slate went out to the world, and the Ffestiniog Railway still runs steam trains from its quay up to Blaenau Ffestiniog. It has fuel, cafes, chip shops and supermarkets. Criccieth's castle on its headland is a short ride west, and Portmeirion's Italianate fantasy village is just across the estuary. Weather in Snowdonia changes quickly; cloud can drop onto the hills in minutes, and the lanes stay greasy long after rain, so ride them with the patience they deserve.