“The fairies were in the habit.. of dancing and singing on the headland across which there are the old earthworks called Dinllaen. When they had played and enjoyed themselves enough, they used to lift a certain bit of sod and descend to their own land...
“...Another woman whom I met near Porth Dinllaen said, that the Dinllaen fairies were only seen when the weather was a little misty.”
from Celtic Folklore, Welsh And Manx, by John Rhys (1901). Online at the sacred texts archive at: sacred-texts.com/neu/cfwm/index.htm