The rise of oil and the supply of cheaper coal from abroad mixed up the Welsh coal industry from the 1950s onwards. One coal mine after another had to close, as did the Lewis Merthyr Colliery.
Doctor Who
The last coal was extracted in 1983, but the mine was given a second life as Rhondda Heritage Park, a museum where former miners can show you around. The underground tunnels were the setting for the Doctor Who episode 'The Doctor's Daughter.'