Single track tunnel carrying the former Manchester & Milford Railway (nprn 91660), later Great Western Railway, later British Railways, line between Aberystwyth and Carmarthen through a ridge of hard rock in Tynygraig village (nprn 402583). It measures 78.79m (86 yards, 6in) long, has brick portals and is brick lined for a short distance at each end, the centre section left unlined. It was opened in 1867 and closed in 1964/5.
B.A.Malaws, RCAHMW, 19 May 1999.