Part of the Elan Aqueduct (nprn 95469), itself part of the Elan Valley Water Scheme (nprn 96459), Dolau Tunnel is about 6.8km long and carries the aqueduct under the uplands between the villages of Dolau and Bleddfa. Its western end is at SO 14149 67316 and its eastern end at SO 20903 68177. A pair of observation towers (nprns 413072 (west) and 413074 (east)), presumably used during the construction of the tunnel, stand on the route, as do two shafts: Graig Shaft (nprn 413073) and Bleddfa Shaft (nprn 413075).
B.A.Malaws, RCAHMW, 17 February 2011.