A stone built retaining wall (visible in May 2000) on the west side of Hill's Tramroad (nprn 85860), to the south west of the south portal of Pwll Du tunnel (nprn 85831) and east of Tunnel Houses (nprn 260527). The structure forms the rear wall of cottages shown at this location on the Ordnance Survey 25in map of 1880 and is part of the approach to the Pwll Du tunnel.
RCAHMW, 05 November 2007.