The disused, Victorian, Cwmorthin Slate Mine is in Blaenau Ffestiniog, North Wales, UK.  It comprises of many miles of tunnels which are mostly between 100-150 years old.  During its operational years it was merged into the nearby Oakley slate mine and is considered to be the largest slate mine  in the world.  Today it is a maze of crumbling, dark passages, littered with items the miners left behind.  A rusting old tea pot sits onto of slate slabs, cut ready for transport out of the mine.  Hobnail boot footprints are still in the mud.  Railway tracks that go nowhere and broken winding mechanisms.  To extract slate and dig tunnels, the miners would drill several feet into the rock and pack the hole with explosives.  The resulting rubble and slate could then be removed and further slate extraction could take place.  There are many places where the drill holes are visible, one is shown in the pictures below.  It's a fascinating insight into a lost world.

Caver David Roberts wearing SRT equipment (Single Rope Technique) which he used to descend a rope into the "Lost World"

Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK

Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UK Cwmorthin Slate Mine, north Wales, UKA rusting miners teapot in Cwmorthin Slate mine, sits on top of a slab of slate that had been in process of being cut into large slabs ready for transportation out of the mine.