Caer Aranrhod (generally known as Caer Arianrhod) is the name given to a group of rocks in the sea about a mile off the coast of Dinas Dinlle, a village on the North Wales coast about six miles from Caernarfon. The rocks are visible only at low tide.
Dinas Dinlle, the site of an Iron-Age fort, is referred to later on in the story as Dinas Dinlleu, spelt in such a way as to suggest a connection with Lleu Llaw Gyffes, Arianrhod’s rejected son.
Caer Arianrhod is also the name given in Welsh to the constellation of the northern sky known as Corona Borealis. This constellation has also been associated with the Greek goddess Ariadne.