We were out of season in Barmouth, and the railway bridge/viaduct over the Mawddach Estuary was closed for refurbishment work.

The bridge/viaduct was constructed of timber in the 1860s, and is being repaired over 3 years using similar materials, except that concrete is used to protect vulnerable wooden parts from attack by marine worms. In season, passengers and cyclists can cross over, which I recall doing with the children many years ago. It is quite a tourist attraction, and rather photogenic.