Bedd Arthur

Bedd Arthur consists of a barely visible oval bank and ditch, with thirteen standing stones, none higher than 60 centimetres (24 in), arranged inside along with two further fallen stones. The stone layout measures around 20 by 10 metres (66 by 33 ft). The shape is not well defined and is generally described as sub-rectangular, but has also been described as a rectangle, a horseshoe, an oval and a pointed ellipse. Similar arrangements of stones are found at a site known as the 'Churchyard' on Skomer Island, and were adopted at Stonehenge, for which Bedd Arthur has been speculatively suggested as a prototype.

The stones appear to be leaning inwards, suggesting that they were originally placed on the flanks of a mound which has since disappeared. There is also one "truncated end", similar to the portal on some elongated Neolithic burial mounds. There may have been a burial chamber in the middle of the stone setting; it would not be exceptional for the mound itself to have been removed by erosion or grave hunters, as may have happened to the Bedd yr Afanc passage grave on the northern side of Mynydd Preseli.

The site has not been excavated and is absent from authoritative surveys. Its authenticity as a site, and any relationship to Stonehenge or local sources of stone, are therefore unconfirmed.

Bedd Arthur sits on top of the Preseli ridge and overlooks the rocky outcrop of Carn Menyn, a site that has been suggested as a source for some of the bluestones used at Stonehenge. A 2011 study of a particular group of the Stonehenge bluestones made of rhyolite identified a geological match with an outcrop at Rhosyfelin, 3 kilometres (1.9 miles) north of Bedd Arthur. A 2015 archaeological study at Rhosyfelin, however, failed to identify any signs of quarrying, which appears to support the possibility that the stones were glacial erratics carried east on an ice-flow, rather than evidence of a Neolithic cultural link between the two places.