There are two cairns on Mynydd Tynewydd, currently in forestry. One of them, Garn Fach, has not conclusively been shown to be man-made.
Like the cairns on nearby Craig-y-Llyn, they are soon to be surrounded by the construction of the Pen y Cymoedd wind farm.
Coflein details:
Y Garn Bica (SN94250051)
A boundary cairn, 10.4m high and 0.6m high, robbed and capped by an OS triangulation pillar.
Garn Fach (SN94490009)
A possible cairn, 5.5m in diameter and 0.6m high.