On the north-west bank of Cwmtillery Lake are the remains of a substantial post-Medieval, stone farmhouse, standing on a large platform cut into the hill and aligned west to east. This site was identified by Lord Raglan and Cllr W. F. Deasy as the remains of Ty Nest Llewellyn or Nest John Rosser, i.e. Nest the daughter of John Rosser. Llewellyn was her married name. Nest was one of the pioneers of Blaenau Gwent Baptist Church and her house was used as a place of worship through a period of religious persecution during the 1660s and 1670s.