The Welsh (Celtic) Mythology is an interesting study for historians and history buffs. I believe the Celtic mythology is not that well known as Greek or Roman mythology.
There is some amazing story about the Celtic moon-mother goddess, called the "silver wheel" also known as Arianrhod.
There intriguing mentions about 'sea spirit', magic rod, mystic ways to test the virginity of a woman etc.
This goddess's mother name is Don. Very interesting. Even I, as typical mathematician that never like history, found myself glued to the rare history book that my husband got it recently in an used books den in Madras.