Visited 11th January: This was the last site we visited, and it was certainly the most beautiful. Access to Gareg Hir is very good, and you can see it from the road. The stone stands on the edge of a forestry plantation, and there's a public footpath running very close to it. We parked in front of the metal gate that bars access to the forestry track, but this wouldn't be ideal for a long visit.
The stone has a lot of modern carving on it (modern as in not prehistoric). There are also some interesting artificial looking horizontal groves on the north facing side of the stone. These may also be modern.
This is a fine stone by any standards, and well worth a visit.
A person residing near Pencader, Carmarthenshire, is reported to have entered the fairy circle on an adjoining mountain, and having danced as he thought for a few minutes, by some means stepped out, but was much astonished to find the scenes to which he had been accustomed, completely changed, and new houses, roads, and improvements, which he had never seen or dreamt of; the place where his father's cot stood, was occupied by a neat and handsome farm house, and where before there was a barren mountain, he saw luxuriant fields.
"This surely, thought he, must be a fairy illusion; I have only been a minute or two in their ring, and lo! they have changed the aspect of nature entirely: I hope what I see is real, and that my father's cot is really converted into that well built farm house." Thus ruminating, and still supposing that what he saw was magic, he proceeded, but his progress was obstructed by a substantial and not an imaginary hedge, he felt, and felt it again, -- rubbed his eyes, thinking he was dreaming, but a thorn running into his hand soon convinced him it was no chimerical scene; indeed the hedge seemed from the size of the thorns to be very old; so proceeding onwards he entered the farm yard, where once stood the cot wherein he first beheld the light of the world: he stared wildly around like one deranged, for a strange dog disputed the ground with im, and by his continued barking informed him he had no right there.
"How can this be, said he? where am I? this is not poor Tango? all seem to be changed! -strange cows- -strange fowls- -strange ducks and geese! surely I have lost my road, and have travelled to an unknown neighbourhood! but no! yonder is the Garreg hir* (the long stone) and I know too well the brow of that hill to be deceived." He was disturbed in this soliloquy by the farmer, who came to know the cause of the dog's barking, and seeing the youth (for he was still one in appearance), addressed him in the common Welsh term, "Pwy' n' ych chwi druan?" (who are you, poor man?") "I know who I was, I do not know who I am now," replied he, "I was the son of a man who lived in this place, this morning; for that rock though changed a little, I too well know to be deceived." "Poor man" said the farmer, you have lost your senses, this house was built by my great grandfather, repaired by my grandfather, and that part there which seems newly built, was done about three years ago at my expence; you must be deranged or have lost the road, but come in and refresh yourself with some victuals and rest."
*The Garreg-hir is a well known erect stone on a mountain south of Pencader, and was placed there in ancient times, probably to commemorate a victory.
You get the idea, and it goes on somewhat more here, in William Howell's 1831 'Cambrian Superstitions'. It's nice though how it uses the stone as an unchanging link with the distant past.