Presaddfed Burial Chamber is thought to date between 4000 and 2000 BC. The remains on this site are of two chambers, one of which has collapsed but the other has a capstone on uprights with some additional support. It is located on a road north of Bodedern village at Brynadfed by the lake of Llyn Llywenan in Anglesey, Wales (Ynys Môn, Cymru).
Link: Cadw - Presaddfed Burial Chamber
Image: Presaddfed Burial Chamber courtesy of Cadw