These standing stones are called Cerrig Meibion Arthur (The Stones of Arthur's Sons) in the Preseli Mountains, Pembrokeshire, West Wales. Traditionally, these standing stones are said to be the graves of King Arthur's sons who were killed while hunting the ferocious Twrch Trwyth, the boar which appears in the tale 'Culhwch ac Olwen (one of a collection of ancient stories found in The Mabinogion)
Ballykeel Portal Tomb (Dolmen). This Neolithic burial site, dated between 4000 and 2500 BC, has a huge capstone, supported on upright stones, over an octagonal burial chamber. It is known as the 'Hag's Chair'. It stands dramatically at the southern end of a long stone cairn. Most of the cairn has gone, but two parallel lines of carefully-set stones defining the edges are still visible. It is located within the Ring of Gullion, an area rich in megalithic sites.