Craig Cwm-Silyn, at a relatively modest 2,408ft, is the highest point of Snowdonia's Nantlle Ridge, known to connoisseurs as one of the finest ridge walks in Wales. Snowdon rises across the valley and, happily, takes virtually all the walking traffic.......
As an added bonus many of the Nantlle Ridge's summits, not least Craig Cwm-Silyn, possess the remains of Bronze Age burial cairns [e.g see Y Garn to the NE] and - better still - the atmosphere to enjoy them in. This summit cairn has been amended to provide shelter from the wind, but nevertheless is a prize well worth seeing, if only as a spot to chill away from the 'civilised' world. To be frank, the views from it's crest are staggering.
"Remains of a stone built cairn on the summit of Craig Cwm Silyn. Roughly circular on plan and measuring about 8.5m in diameter and up to 2m in height. A modern walker's shelter has been constructed within its summit"..... so says Coflein.
Once when William Ellis, of the Gilwern, was fishing on the bank of Cwm Silin Lake on a dark misty day, he had seen no living Christian from the time when he left Nantlle. But as he was in a happy mood, throwing his line, he beheld over against him in a clump of rushes a large crowd of people, or things in the shape of people about a foot in stature: they were engaged in leaping and dancing. He looked on for hours, and he never heard, as he said, such music in his life before. But William went too near them, when they threw a kind of dust into his eyes, and, while he was wiping it away, the little family took the opportunity of betaking themselves somewhere out of his sight, so that he neither saw nor heard anything more of them.
This is in 'Cymru Fu', edited by Isaac Foulkes (1862), which is in Welsh, but I have taken it from John Rhys who considerately translated it in his 'Celtic Folklore' of 1901.