There's a remarkable amount of fairy folklore that goes with this area. You can't help thinking that it's connected with the remains of the prehistoric huts and fields that are here. http://www.coflein.gov.uk/en/site/95402/
My next informant is Mr. Hugh Derfel Hughes, of Pendinas, Llangedai [..] Mr. Hughes says that he has lived about thirty-four years within a mile of the pool and farmhouse called Corwrion, and that he has refreshed his memory of the legend by questioning separately no less than three old people, who had been bred and born at or near that spot. [..]
"In old times, when the fairies showed themselves much oftener to men than they do now, they made their home in the bottomless pool of Corwrion*, in Upper Arllechwedd, in that wild portion of Gwynedd called Arvon. On fine mornings in the month of June these diminutive and nimble folk might be seen in a regular line vigorously engaged in mowing hay, with their cattle in herds busily grazing in the fields near Corwrion. This was a sight which often met the eyes of the people on the sides of the hills around, even on Sundays; but when they hurried down to them they found the fields empty, with the sham workmen and their cows gone, all gone. At other times they might be heard hammering away like miners, shovelling rubbish aside, or emptying their carts of stones. At times they took to singing all the night long, greatly to the delight of the people about, who dearly loved to hear them; and, besides singing so charmingly, they sometimes formed into companies for dancing, and their movements were marvellously graceful and attractive.
There's a great deal more - it runs on for about 20 pages with numerous tales of fairy romance, fairy cattle, the power of iron, rumours of lost churches, ghosts, (and does mention the hut circles briefly).. it's quite a place for such strangeness so it would seem. From Y Cymmrodor 1881, in a chapter on 'Welsh Fairy Tales' by Professor Rhys (doubtless John Rhys of 'Celtic Folklore, Welsh and Manx').