Zip World Caverns

You're about 300 metres underground in a flooded slate cavern, harnessing yourself to a rope and preparing to abseil into the dark. Zip World Caverns, just outside Blaenau Ffestiniog, turns an old Welsh slate mine into something genuinely thrilling - part adventure sport, part industrial archaeology.

The whole experience is daft fun. You get kitted out above ground, then descend into the cathedral-like spaces where miners extracted slate for well over a century. The main event is the abseil down into the flooded chamber - it's genuinely vertiginous and the water at the bottom looks black as ink. There's also a zip line that shoots you across a void if you want the adrenaline hit without the climbing.

It's not for the faint-hearted or anyone with a genuine fear of heights. You need to be reasonably fit and comfortable on a rope. Kids can do it from around age eight upwards, depending on nerve and build. Allow about two hours total - longer if you're nervous or want to soak in the weirdness of the space.

Stay at Llechwedd Glamping, literally down the road, and you've got the perfect base. It's close enough to roll back after an adrenaline spike. Bryn Dinas Camping Pods, five miles away, gives you a bit more breathing room if you want quieter surroundings. Either way, this isn't your average rainy-day activity - it's the sort of thing you'll be talking about for months.