As well as the summit cairn, there is a further round barrow at the northwestern end of the Black Mixen summit ridge, Mynydd Ffoesidoes, at SO19096521.
Coflein description:
The monument comprises the remains of a substantial round barrow, a burial mound probably dating to the Bronze Age (c.2300 BC – 800 BC) and situated in enclosed rough moorland on the NW end of the Black Mixen ridge on Radnor Forest. The heather-covered barrow is circular on plan and measures about 24m in diameter and up to 1.3m in height. Although the W side of the monument has been disturbed and is generally lower, the base of the round barrow appears to be undisturbed. Traces of a surrounding ring ditch are visible, in places measuring up to 2m in width. The barrow is situated within boggy moorland – a Site of Special Scientific Interest – and has great archaeological and paleoenvironmental potential. The barrow possibly represents the remains of a platform cairn – the barrow displays no evidence of original ‘bulk’ indicating a rounded profile and is unlikely to have been extensively robbed.