The deepest mine in south Wales. Nantgarw Colliery was one of the flagships of the National Coal Board. It was the nearest deep mine to Cardiff, and a reminder to travellers that they had entered the south Wales coalfield. Opened in 1911, it boasted two large shafts and, at a depth of 782.73m (856 yards), was the deepest mine in south Wales. However, despite appearing as a fine example of a clean and efficient modern coal industry, the colliery was abandoned in 1927 due to lack of manpower, poor industrial relations and, above all, being located above very complex underground geology.