Cardigan Bay to the west and the surrounding hilly geography made it difficult for foreign invaders to conquer.

Tradition found in the work of Nennius, a 9th century Welsh chronicler, traces Ceredigion's foundation to Ceredig, son of Cunedda.

These statements may be simply mistakes, or they may be echoes of the fact that the kings of Ceredigion conquered Y Cantref Mawr in, the eighth century.

[4] The same authority on Welsh topography also deals with the statement given in the Life of St. Carannog, that the River Gwaun, which flows into the sea at Abergwaun (Fishguard), formed the southern boundary of the kingdom, and shows that in an older version of the same, the Teifi is represented more correctly as the southern boundary.

The substitution of the Gwaun for the Teifi, is due to the inclusion, in 1291, of the deaneries of Cemaes and Emlyn with Ceredigion, in the Archdeaconry of Cardigan.