(Photos 9 © Transport Treasury/Richard Riley)
Opened in 1868, Cefn Coed Viaduct was built to carry the Brecon & Merthyr Railway over the River Taff. Contractors Savel and Ward erected it at a cost of £25,000.
Consisting of 15 arches, each one almost 40 feet across, the structure boasts an elegant curve, a length of 257 yards and a maximum height of 115 feet.
The line over it was closed to passengers in 1961 but goods services continued to run until 1st August 1966.
Today it is crossed by the Taff Trail footpath.