An impressive, lofty, dry-stone causeway, built partly on a curve, which carries the Ffestiniog Railway (nprn 34660) across the valley of the Afon Caefali.
The causeway is approximately 175m long overall and 19.1m high from stream bed to rail level. It is 4.5m wide at the top and the culvert is 19.0m long. There is a low parapet wall on the north side, and remains of a similar wall on the south, although this has gone completely on one stretch of 42m at the west end. Several two-hole stone sleeper blocks are visible in the capping of the parapet walls.
B.A.Malaws, RCAHMW, 25 February 1992.