They [the Druids] had their groves, the till then inseparable concomitants of the Druidish priesthood, which the sacrilegious Romans immediately cut down and demolished. And to this day here are places retaining the ancient name of Llwynau or groves, as Llwyn Llwyd, Llwyn Moel, Llwyn On, Llwyn Ogan, and Llwyn Coed, in or near every one of which may be remarked some remains of Druidish worship; either broken altars, pillars, or remains of a Carnedd. And no doubt there were many more groves, whose names are lost and quite forgotten.
It being now made somewhat apparent on the evidence produced, that the Chief Druidical residence was in the Isle of Mona, and particularly in and about the place now called Llanidan parish; it may then be expected that that place of all the island, must be at that time most plentifully adorned with a variety of formed groves, containing in them mounts, pillars, heaps, altars, and other appurtenances of their superstitious worship. And that although the groves surrounding them be now quite gone and perished, and the ancient names of them be utterly lost, yet it may be justly expected that many of the more lasting erections (on the supposal I offer) should remain there, as standing monuments of their long forgotten superannuated uses. And indeed in that respect there are of such enough to answer the end, and to give sufﬁcient satisfaction to a just and reasonable enquirer.