In the road near Caerau, and opposite the second embankment (Caerau consists of three concentric, circular embankments within and above each other at intervals of about twenty yards ; with an elevation in the second of two feet, and in the third, or innermost, of four feet). There are some men living who remember these embankments much higher than they are at present ; particularly the innermost agger, which on the seaward side was about ten feet, is a hollow which rings when any wheeled vehicle goes over it. About eighty years ago two men had the curiosity to dig there, and they solemnly declared that they came to the frame of a doorway ; but when they went to dinner, the rain descended, accompanied by thunder and lighting, and on their return the whole was closed, as they supposed by supernatural agency. A little above the place where they had been digging they affirmed that there had been no rain.
At Castell Ion some stairs were seen, supposed to lead to some passage. A farmer's wife about ninety years since, having risen very early one morning, was thus accosted by a woman bearing the semblance of a gipsy : '' Would you like to take your rest of a morning instead of leaving your bed so early ? " " Yes," was the reply.
" Then," said the woman, " if you dig in a certain spot in the subterranean passage between Caerau and Castell Ion, you will find what will make you the richest lady in the land."
About sixty years ago a respectable man declared that he was cutting a hedge between Trefas and Pant y Groes when a grey-headed old man came to him and told him that there was an underground way from Caerau to Pentre-Evan ; and that if he excavated a certain place he would find two hundred " murk " (? marks).
A woman once appeared to a ploughboy and told him that there were ten murk under the threshold of Caerau Bach. When the cottage, which had been probably built on the site of the outpost referred to, was taken down, a number of people assembled to search for the marks, but none were found.
From Henry Vincent's article on 'Caerau in the parish of St Dogmells' in Archaeologia Cambrensis, Oct. 1864.