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.
Ar lan gogledd-orllewinol Llyn Cwmtyleri mae olion ffermdy carreg sylweddol ôl-Canoloesol ar lwyfan mawr a dorrwyd i’r bryn ac a gyfluniwyd o’r dwyrain i’r gorllewin.
Dynododd yr Arglwydd Rhaglaw a’r Cyng. W. F. Deasey y safle fel olion Ty Nest Llewellyn neu Nest John Rosser.
Llewellyn oedd ei henw priod. Roedd Nest yn un o aelodau cyntaf Eglwys Bedyddwyr Blaenau Gwent a defnyddiwyd ei chartref fel man addoli drwy gyfnod o erledigaeth wleidyddol yn ystod y 1660au a’r 1670au.