Railway Viaduct over Canal to SE of Govilon

This is a single-arch railway viaduct built in the 19th century to carry the Merthyr, Tredegar and Abergavenny Railway line over the Brecknock and Abergavenny Canal (now the Monmouthshire and Brecon Canal) to the southeast of Govilon. The railway line, incorporated in 1859 and initially running from Nantyglo Ironworks to Govilon Wharf, was leased to the London and North Western Railway in 1862 to capitalize on the region's growing heavy industry. Construction of the railway line was considered a significant engineering achievement due to the steep gradient of the Clydach Gorge, requiring specially designed locomotives. The canal itself was constructed between 1797 and 1812, and later acquired by the Great Western Railway after the railway gradually diverted traffic from the canal.

The viaduct is built of rock-faced rubble with a red brick soffit, featuring a band course. It is situated at a skewed angle over the canal. Evidence of a later, likely late 19th-century widening is visible, with a clear break in construction approximately two-thirds of the way along the soffit. Different voussoirs on the western and eastern segmental arches confirm this widening, with vestiges of original yellow brick voussoirs visible at the joint of the western arch. The eastern side (Llanfoist) uses flush yellow brick voussoirs, while the western side (Govilon) incorporates blue brick voussoirs laid in five oversailing, toothed courses. Angled rubble abutments are present on both sides. Original iron parapet rails remain on the eastern side, but a more modern timber parapet exists on the west. A towpath is located to the south side of the canal, with a further path to the north.

The viaduct is listed for its architectural interest as a good example of a 19th-century skew-arch railway bridge, and for its group value with other listed canal structures in the vicinity of Govilon.