The summit hosts a very large Bronze Age round barrow which is in a degraded state and remains unexcavated. However, there are similar burial cairns at the summits of Pen y Fan and Fan Foel. The latter was excavated in 2002-4 with the results published in 2014 in Archaeologia Cambrensis. The round barrow was about 16 meters (about 52 feet) wide and was badly eroded with stones from the structure removed to build a central cairn by passing walkers. Excavation of the barrow showed that it contained two separate burials, the central one in a stone cist contained the burnt bones of an adult woman and two children carbon dated to about 2000 BC. It is likely that the barrow on Picws Du is of a similar age when the climate was much warmer than today, and the now deserted sub-arctic and tree-less landscape supported a larger human population than at present.