On the summit are the remains of two prehistoric burial cairns. The Great Cairn is at the highest point and measures about 1m high, 36.5 metres from north to south and 43m from east to west. It appears to have been a Neolithic passage tomb, dating to 3300-3000 BCE. It is the highest known passage tomb in Britain and Ireland. The Lesser Cairn lies 210 metres to the northeast, overlooking Newcastle. It measures about 4.5m high, 18m from north to south, and 16m from east to west. It appears to have been an Early Bronze Age multiple-cist cairn, dating to 2300-1950 BCE. In the past, the cairns had a much more well-defined shape and it is thought the Great Cairn had an east-facing entrance leading to an inner chamber. They appear to parallel the two cairns on Slieve Gullion, which can be seen from Slieve Donard.