hit on “sinking lands wales”:
http://www.geocities.com/athens/forum/7280/welsh.html
Anglesey - once joined to Carnarvon by the tall forests of the Sinking Lands. It is separated from the Island of the Mighty by the Straits of Menai.
Bran the Blessed - first born of Llyr and Penardim; nephew and successor to Beli of the Deep as High King of the Island of the Mighty. He led the hosts of the Island of the Mighty against King Matholuch of Ireland to avenge the wrongs committed to Branwen, Bran’s sister and Matholuch’s wife. Being of unusually large proportions, Bran was forced to wade through the Sinking lands to reach Ireland. On returning, he was ambushed at Morddwydtyllyon, and received a fatal wound from Matoluch. Bran was called “ancestor to many saints.”
Carnarvon - once joined to Anglesey by the tall forests of the Sinking Lands.
Casket of Ancient Spells - saved from the Sinking Lands and brought to the Island of the Mighty. Although Math would have returned them to the Lost Lands of the West, Don preserved them, telling only Arianrhod of their hiding place. Its power contributed to the destruction of Caer Arianrhod.
Hu the Mighty - killed a man for bringing the Casket of Ancient Spells from the Sinking Lands.
Lost Lands of the West - through the use of powerful magic such as that contained in the Casket of Ancient Spells, the sea rose up and claimed these lands. They may have been connected to the Sinking Lands. Caer Sidi was probably its capitol.
Sinking Lands - its tall forests once joined Anglesey to Carnarvon. The hosts of Bran crossed it to reach Ireland. Bran himself waded across. They may have been connected with the Lost Lands of the West.
The Snowdonia Mountains is where I believe Bron-y-Aur is located, which is where much of Led Zeppelin’s third and fourth album material was created.