Portal dolmens are funerary and ceremonial monuments of the Early and Middle Neolithic period, the dated examples showing construction in the period 3500- 2600 BC.
As burial monuments of Britain's early farming communities, they are among the oldest visible field monuments to survive in the present landscape. A massive capstone covers the chamber, and some examples show traces of a low cairn or platform around it. Some sites have traces of a kerb around the cairn and certain sites show a forecourt area often edged by a facade of upright stones.
Little is yet known about the form of the primary burial rites. At the few excavated sites, pits and postholes have been recorded within and in front of the chamber, containing charcoal and cremated bone; some chamber contents of soil and stones may be original blocking deposits.
Many portal dolmens were re-used for urned cremations, especially during the Middle Bronze Age. Only about 20 are known nationally, mainly concentrated in Penwith, West Cornwall. Despite having collapsed and some disturbance by cultivation, the portal dolmen called The Giant's Quoit at Carwynnen is still one of an extremely ancient and rare group of monuments. It will retain archaeological and environmental evidence relating to its construction, function, longevity, funerary and ritual practices, social organisation, territorial significance, collapse, reconstruction and overall landscape context.
Notes accompanying the Greig engraving of 1808 state " There is at present little doubt among antiquaries with respect to the original designation of the Cromlech; it is generally believed to be a sepulchral monument used by the druids to mark the places of interment of the Druid chief, or such princes as were favourable to their order."