Perthi-Duon Burial Chamber is in Anglesey, Prehistoric Anglesey Burial Chambers.
Perthi-Duon Burial Chamber [Map]. Possibly just a boulder in a field? Or, a collapsed burial chamber, consisting of a 2.5 metres by 1.8 metres capstone lying on two collapsed stones, which may have been the upright stones. Multiple stones surround the monument. The site was examined as early as 1723, when Henry Rowlands, an antiquarian, visited and drew the tomb, which at the time stood upright.
Archaeological Journal Volume 28 1871 Pages 97-108. 4. Perthi-duon [Map], Llanidan par. (s). The late Rev. H. Longueville Jones notices a cromlech near the old church, to S.W., partly demolished. Arch. Cambr., new series, vol. v. p. 206. See also a note of this cromlech, ibid. vol. i., first series, p. 467, where it is stated that "copper chisels" were found under it, about 1825. Compare a tradition under Caer-llechau, infra. No. 8.