Pont y Cafnau (The 'Bridge of Troughs') is a small bridge and water feeder (probably the oldest known iron railway bridge and aqueduct) spanning the River Taff immediately downstream from the junction of Taf Fawr and Taf Fechan. The bridge and aqueduct was built in 1793 and comprised a trough to carry a low lever water feeder from the Taf Fechan to the Cyfarthfa Iron Works, over which was laid a 4-foot gauge tramroad which was part of the railway system between the Gurnos Limestone Quarries and the ironworks. It also supported a second, high level aqueduct which fed the great Aoelus waterwheel at Cyfarthfa.