Great Orme copper mine.

This place is amazing.
One word of caution, wear the safety hat they provide. I lost count of the times I cracked my head on the roof, without the hat I'd be sporting a few stitches.
The tunnels were built and used by kids so some are low and narrow. I actually had to turn sideways in some places which makes it difficult to duck, if you're on the chubby side you may not fit.
The visitor centre/shop has a decent collection of stones and minerals to buy. I got myself a nice geode and a piece of slate with a fossil of a trilobite, the first land creature to have eyes.
It's really worth a visit and a bit further on is the summit complex with some nice views, of course it was wet and dismal when we went.

Great Orme copper mine
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