Possible burial chamber, comprising a substantial boulder (possible capstone), the western end of which rests on a large boulder and with a number of smaller stones beneath.

Noted on the first edition (1868-1892) 25-inch Ordnance Survey maps as a Cromlech and continues to be noted as such through to the 4th-edition mapping.

Writing in Archaeologia Cambrensis it is disputed by Anwyl in 1904, but classified as a cromlech by Williams in 1922.

Described with no clear conclusion in the RCHAMW Caernarfonshire Inventory (1960):

(1252) BURIAL CHAMBER (?) near Bryn, at 220  ft. above O.D. The capstone, 12 ft. by 8 ft. 6 ins. by 3 ft. 6 ins., rests at one end on small stones and at the other on a fallen upright, 5 ft. 3 ins. by 4  ft. 6 ins. by 2 ft. 6 ins.  There is no sign of a mound. The remains have sometimes been regarded as of natural origin. 

Assessed by Gwynedd Archaeological Trust (2002):

An unconvincing but confusing site. Set in an ideal place for a chambered tomb, overlooking the Menai Straits. W end of the large ‘cap stone’ rests on a large boulder which could be a collapsed upright, though there is no trace of the hole in which this might have stood. There is no comparable upright for the E end. The other stones around are much smaller and most are clearly recent field clearance additions. Only a substantial stone could support the massive capstone and it seems highly unlikely that the stone would have been removed. There is no structure or order to the feature and if the stones were smaller there would be no doubt about saying that this was just a heap of field clearance stones. Why the huge ‘capstone’ should have been moved and how it was dumped on top of an existing collection of field clearance stones is not clear, but this is what it looks like, unless it is an unfinished monument, the smaller stones being packing during elevation of the capstone. There is a reference to the site at least as early as 1904 so the large stone has not been moved by modern plant. Nevertheless it is not convincing as a burial chamber. Siting - on level natural terrace in gentle slope leading down to Menai Straits. (Smith, 2002)

Louise Barker, RCAHMW, August 2022

Sources:

Anwyl, E., 1904, Early Settlers of Caernarvonshire. Archaeologia Cambrensis 4 (6th Series) (pg 198)

RCAHMW, 1960, Caernarvonshire Vol II: Central. A Survey and Inventory by The Royal Commission on  Ancient and Historical Monuments in Wales and Monmouthshire (1252 pg 201)

Smith, G., 2002, Survey of Prehistoric Funerary and Ritual Monuments in Wales: West Conwy and North Gwynedd (Gwynedd Archaeological Trust)

Williams, A., 1922, Notes. Archaeologia Cambrensis 2 (7th Series) (pg 158)