national park in Gwynedd county and Conwy county borough, northern Wales, with an area of 838 square miles (2,171 square km). It is best known for its mountains, composed largely of volcanic rock and cut by valleys that show the influence of Ice Age glaciers. Snowdon mountain's summit, Yr Wyddfa, in the northwestern part of the park, is the highest peak in England and Wales, with an elevation of 3,560 feet (1,085 metres). A rack-and-pinion railway (opened 1896) runs from Llanberis to the summit. Farther south Cader Idris (“Chair of Idris”), a long mountain ridge, reaches a height of 2,927 feet (892 metres) at Pen-y-Gader.

Tourism thrives, stimulated by the possibilities for climbing, hill walking, fishing, and sightseeing. Tourist centres in and near the park include Bala, with recreational facilities on Bala Lake, the largest natural lake in Wales; Betws-y-Coed, noted for its waterfalls, wooded gorges, and picturesque bridges; Blaenau Ffestiniog, where the defunct Llechwedd Slate Caverns are open to visitors; Dinas Mawddwy, with a textile mill and craft shop oriented toward touring shoppers; Dolgellau, overlooked by Cader Idris; the old village of Ffestiniog, on a bluff above the wooded Vale of Ffestiniog; Llanberis, at the foot of Snowdon, facing the massive Dinorwic slate quarries; and the Cardigan Bay resorts of Harlech, Barmouth, and Aberdovey.