Yr Arddu, Snowdonia National Park

Yr Arddu is a large hill in Snowdonia, Wales. It lies approximately 2.5 km south east of the village of Beddgelert and just over 1 km from the rather more famous mountain Cnicht. It is a rugged hill with widespread rock outcrops and cliffs. A small lake, Llyn yr Arddu, is located on the flanks of the mountain. The recognised summit is at 388m to the South of the hill, but the highest point, named Cerrig-y-Myllt on only the most detailed UK Ordnance Survey mapping, is at 463m above the two small lakes to the North of the hill. The craggy nature of the hill is due to the presence of lavas and tuffs dating from the Ordovician period when Snowdonia was characterised by numerous volcanic eruptions; Yr Arddu is a particularly good location to see the record of Ordovician volcanism. The Yr Arddu Tuffs may be the earliest eruptive phase of the Lower Rhyolitic Tuff Formation. ()