Formed in 1951, Eryri is the largest national park in Wales, and includes the highest mountain in Ireland, England and Wales, and Wales' largest natural lake. The area is steeped in culture and local history, where more than half its population speak Welsh[7] Fossil shell fragments on the summit of Snowdon date from over 500 million years ago and the ancient ‘Harlech Dome’ of which Snowdon and Cadair Idris form the northern and southern extents respectively, was created in the Cambrian Period before the volcanoes erupted. The more recent Ice Age glaciers were at their peak 18,000 years ago in Snowdonia and formed the distinctive U-shaped valleys including Llanberis and Nant Gwynant in the north and Tal-y-llyn Lake in the south.[8]