Cymmer Viaduct

Cymmer Viaduct is a wrought-iron lattice-girder viaduct built with a slightly curved deck, aligned roughly north to south. The main abutments are made of coursed rock-faced stone and feature a round arch with a keystone, above which is a string course and a coped parapet. The arches are flanked by round turrets that rise to the full height of the parapets. On the northern side, the parapets curve outwards and end in square piers. The southern side has an additional abutment that supported a second girder bridge over the nearby former Rhondda and Swansea Bay Railway, which is now the Afan Valley Cycle Way.

The lattice girders rest on three tapering rectangular piers made of rock-faced stone with moulded copings. The girders are constructed in four straight sections and still have some timber cross members on the deck.