Their habitations were universally believed to be underground, in dimly lit regions, with the entrance to them under a sod, near one of their circles, by some ancient standing stone, under the bank of a river, away on the open moor hidden by bushes, or in the ruins of an old castle, as on Ynys Geinon rock. In the midst of this castle there was a pit with a three-ton stone lying across it, and when they wanted ingress or egress, they uttered a secret word, and lo! the stone lifted, and fell back again of its own accord. From the entrance down to the underground passage they descended along a ladder of twenty-one or –two gold rungs. D. Parry-Jones, Welsh Legends and Fairy Lore, 19