The only existing cromlech in the parishes of Llanllechid and Llandegai is situated in the upper part of the parish of Llandegai, near a small farm called Ffynnonbach. It goes locally by the name of “yr hen allor” (the old altar), and tradition, as usual, ascribes its erection to the Druids; and the use to which it is said to have been applied, is indicated in its being called an altar. But that the cromlech was a mere burial-place, has long since been settled. The cap-stone measures in breadth 5 feet; in length, 14 ft. 5 ins.; in thickness, about 1 ft. 6 ins. throughout.
More on the state of the stones in 1867, along with associated finds, in volume 13, series 3 of Archaeologia Cambrensis, viewable at the Internet Archive.