Talywain or Garndiffaith Viaduct has nine semi circular 15 metre (50 foot) arches carried on tall, slightly battered piers. The structure opened in 1876-7, built by John Gardner Esq. It is composed of squared rubble with ashlar impost mouldings and brick voussoir. The viaduct was built to carry the London & North Western Railway on the Abersychan & Talywain to Brynmawr line.

Claire Parry, RCAHMW, 26 July 2011.

Source: A Guide to the Industrial Archaeology of South East Wales, AIA, 2003