This round cairn is found very close to the mast that is on the summit of the mountain in between Aberdare and Merthyr (SO 0201 0528). The diameter of the cairn is 6.1m and its height 0.6m. Two loose slabs are at the centre- this may possibly be what remains of a cist. This cairn is found on the edge of the moorland plateau while another is found next to the mountain trackway. The measurements are the same as the first. Round cairns are from the Bronze Age, particularly 1700 and 1200 B.C.
Ref. Royal commission on Ancient and Historical Monuments in Wales : Glamorgan Vol.1 Part1,Tthe Stone and Bronze Ages. 1976. Page 67. CADW Scheduled Ancient Monument Record : GM402(RCT) Carn Pentyle-Hir & Adjacent Round Cairn. (Report).