G.B. WALES. Blaenavon World Heritage Site. Blaenavon illustrates the pre-eminence of South Wales as the world's major producer of iron and coal in the 19th century. There are remains of the coal and iron ore mines, quarries, a primitive railway system, furnaces, the homes of the workers, and the social infrastructure of their community. The former Big Pit Colliery which was closed in 1980 and is now a visitor centre. 2004.