The Quarry Explorer attraction at Llechwedd Slate Caverns in North Wales opened on Saturday, 21 May.
Mining began at the site in the mid-1800s and huge piles of stone were discarded as 90 per cent of the rock blasted out of the earth proved unusable.
The spoil was carried to the surface using pulleys and carts and left in towering heaps, which now reach up to around 4300 metres above sea level.
The Llechwedd slate mine is now the subject of a UNESCO World Heritage Status bid.
The underground mine extends down 16 floors and contains more than 32km of hand-cut tunnels and caverns.
Visitors can go to the top of the quarry’s peaks and into craters in off-road former military vehicles while learning about the site’s history.
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