The southern portal of Pwll Du tunnel (nprn 85830), carrying Hill's Tramroad (nprn 85860). The tunnel was probably made from the northwards extension to Pwll Du in 1815 of a mining level in the hillside north of Blaenavon Ironworks (nprn 34134). In July 2000, the portal was half buried and blocked but the top of the arch of white-brick voussoirs was visible.
RCAHMW, 06 November 2007.