Came across this feature recently whilst ascending Arenig Fach from Llyn Celyn... looks rather like a trashed round cairn to these eyes, but nothing is listed on Coflein or the local Gwynedd Archaeological Trust records - although GAT does list a 'lost' cairn [supposedly at SH84604050] last seen in 1913... [PRN4726]. Even the field hasn't been identified since... I reckon this is too far south to relate to the feature, but if it's lost, who knows?
Any thoughts welcome - or if you're passing that way and fancy a look...