The Carneddau Hengwm are two enormous Neolithic long cairns.

Carnedd Hengwm South is the larger at 46 metres long and 3 metres high in places. It has a collapsed dolmen at the eastern end and a virtually intact burial chamber in the Cotswold-Severn style with large capstone and lateral passage leading from the northern edge. Another chamber with no capstone and no apparent passage is also visible on the southern side. The two styles of chamber (dolmen and lateral passage) suggest that this is a multi-period cairn used and extended over a long period of time.

Carnedd Hengwm North is the smaller (only 30 metres!) and has two denuded but clearly visible chambers again in the lateral passage Cotswold-Severn style at the eastern end. There is a large capstone at the western end which may have once covered another possible chamber towards the centre of the cairn.

Location: Near Dyffryn Ardudwy, Gwynedd, Wales
Grid Ref: SH61342052