It is Black Rock Sands Sea Cave(s). If Graigwen's beach is in North Wales, it'll be that - I'm not aware of any other North Wales beach you can go zooming round by car. So any of you two can have it.
Well I did say Black Rock! I was quoting a bit of Robert Graves poem "Welsh Incident" - he used to live across the estuary in Harlech:
"
But that was nothing to what things came out
From the
sea-caves of Criccieth yonder.'
'What were they? Mermaids? dragons? ghosts?'
'Nothing at all of any things like that.'
'What were they, then?'
'All sorts of queer things,
Things never seen or heard or written about,
Very strange, un-Welsh, utterly peculiar
Things. Oh, solid enough they seemed to touch,
Had anyone dared it. Marvellous creation,
All various shapes and sizes, and no sizes,
All new, each perfectly unlike his neighbour,
Though all came moving slowly out together.'
'Describe just one of them.'
'I am unable.'
'What were their colours?'
'Mostly nameless colours,
..........." and so on.
Incidentally, I don't think the rock is dolerite, it is very fine grained, more acidic I guess.
Obviously I am happy for "me" to continue as he has better photos than I have!
And once again I have no clue what his photo is of.
.