Part of the Elan Aqueduct (nprn 95469), itself part of the Elan Valley Water Scheme (nprn 96459), Pant-y-war Tunnel is 470m long and carries the aqueduct under the eastern flank of Glog Hill. Its southern end is at SO 23358 68242 and its northern end at SO 23545 68668. There is an outlet chamber at SO 23479 68504 and two spoil tips are shown just to the east of this on the second edition Ordnance Survey 25in mapping of 1903; the outlet chamber may have been used for removing spoil from the tunnel during construction.
B.A.Malaws, RCAHMW, 16 November 2010.