In Pictures: A record of disused slate mines in Wales

The so-called "bridge of death" at Moel Fferna slate mine in noth Wales. (Photo: Simon Lowe)

Cavers have captured some extraordinary images of abandoned slate mines. This bridge - dubbed the "bridge of death" - was used for generations at Moel Fferna, a slate mine in north Wales.

Moel Fferna is the kind of location which draws a group of photographers with a fascination for disused mines and quarries. They aim to build an online record of the UK's underground industrial heritage.

An explorer crosses the remains of a bridge in Croesor Rhosydd mine. (Photo courtesy: Simon Lowe)

With skills and equipment used in the sports of caving and potholing, they carry their lights and cameras far underground to places where once men earned a living, perhaps with just hand tools and candles for illumination.

A group of explorer study a cathedral-size underground chamber. (Photo courtesy: Simon Lowe)

Photographer Dafydd Jones said: "It's quite a humbling experience to walk through the abandoned chambers of mines - some can be as large as cathedrals - and realise the toil and hardship that went into creating them."

The remains of a bridge crossing water in Croesor Rhosydd slate mine, near Blaenau Ffestiniog, Gwynedd. (Photo courtesy: Dafydd Jones)

As they are no longer maintained, water in the mines can collect as cold underground lakes, providing an extra hazard for the unwary and untrained. The photographers ask the land owner's permission where needed.

A walkway around an underground slate cavern, with graffiti left by miners (Photo: Simon Lowe)

North Wales once had a thriving slate mining industry, leaving some 600 open pits and quarries and dozens of mines. The men working in this mine left their initials as a clue to who they were when it closed in 1960.

A climber uses the wall to cross above an unstable rusting and rotting bridge (Photo courtesy: Dafydd Jones)

The mine workings are often fragile and close to collapse. It can lead to some spectacular - if a little off-the-wall - images but safety remains paramount for the clubs and groups which do it.

Dafydd Jones said: "A rockfall at the Bowydd pit in Blaenau Ffestiniog in January underlines the need for such record-keeping - it destroyed a machine-bored tunnel from around 1864 unique in the Welsh slate industry."

An explorer crosses a modern ladder bridge in Croesor mine (Photo courtesy: Simon Lowe)

Even modern equipment is at risk. This ladder bridge in Croesor mine has since been destroyed by a small roof fall.

Apartially submerged slate slab wagon, Cwmorthin slate mine. (Photo courtesy: Simon Lowe)

Dafydd Jones said: "It reminds us that we're merely seeing a "snapshot" of what once existed - and we have a unique opportunity to record history for a future in which it may no longer be able to experience these mines."