I wonder if anyone knows where this stone is. It's supposed to be near the Valley of the Stones, on the Porth Dafarch road on Holyhead. There's a picture here
http://www.caergybi.com/images.php?pageno=770402006
which looks quite standing stonish. But maybe if it's near a 'valley of the stones' and it has got quite a nibble out of it, maybe it's not a prehistoric stone at all. I can't see it on Coflein.

It's got some attendant folklore -
http://www.bbc.co.uk/wales/northwest/sites/holyhead/pages/weird.shtml

"Liz (Canada)
To Stacey, Manchester: Yes, I know that stone on Porthdafarch Road. We called it "Careg y Bwgan" (The Ghost Stone). We always were told that if you walked around it with your eyes closed - you'd find yourself INSIDE the stone! Needless to say, although I scoffed at the story, I never walked around it 3 times with my eyes closed! Anyway, does anybody know how this huge stone came to be standing there? A relic of the distant past perhaps? Any ideas?

Stacey Manchester (formerly Holyhead)
I can't believe no one has mentioned the Bogey Stone on Porthdafarch Road. A 300 year old legend states that if you walk around the Bogey Stone (at Witching Hour any night in August) 3 times, you will see a man on horseback at the entrance to the stone, whose head hangs off! The legend states that this guy was a highwayman that used to hide behind the rock and pounce on the rich to steal their goods while travelling. Apparently caught in a battle with a travelling soldier, the man was beaten and killed, but his head wasn't fully dismembered, hence it hanging off! They say that his spirit stays there waiting to exact his revenge on the soldier who finally put his robbery to an end. "