The ruins of two adjacent Neolithic megalithic tomb chambers lie on level ground at the southern end of Llyn Llywenan. The southern chamber is about 2.5m across and has four upright stones standing about 1.1m high supporting a monumental capstone 4.2m by 3.3m and 0.7m thick. Only one stone remains upright of the second chamber, about 2.0m to the north. This is 1.8m high. Two other stones recline against it and a capstone lies on the ground nearby. The two chambers do not appear to have communicated directly although they were probably embedded in a common mound or cairn, of which no trace now remains.

Sources: RCAHM Anglesey Inventory (1937), 18
Lynch 'Prehistoric Anglesey' (1970), 51

John Wiles, RCAHMW, 9 August 2007.