Dinas Emrys is in the Snowdonian Mountains of Northern Wales. It is north of the town of Porthmadog. The site has legendary connections to Vortigern . Nennius, a 9th-century writer, tells of Vortigern, Merlin, Ambrosius, and the two sleeping dragons (one red and one white) who awoke and fought for the supremacy of Wales.
The ruins of Dinas Emrys are on top of a craggy hill and may well have been the strongest natural fortress in Gwynedd. . The ruins were different from the other forts. There was no circular "banks-and-ditches" layout, and no large central area. The whole area is very rocky, and there were remains of several structures, at least one of which is Roman. There were two prominent foundations remaining, each with walls several feet high
The pool of the Vortigern story is there today, a rectangle dug during the first century AD. It is difficult to determine the dimensions because of the tall grasses growing in it. The association of Vortigern with Dinas Emrys is strengthened by the discovery of Tintagel pottery during excavations, which is indicative of a certain degree of prosperity in 400-600 AD.