Tradesman's Entrance (C)

You'll find the entrance tucked into a hillside near Neath - easy enough to spot if you know where to look, but the kind of place that rewards a bit of poking about. Tradesman's Entrance is a proper working cave system, the sort of thing that gets geologists properly excited but won't leave casual visitors baffled. It's free to visit, which is brilliant, though you'll want to bring a torch and sensible shoes because it's damp underfoot and the path narrows once you're inside.

The cave itself isn't vast - you're not talking Mammoth Cave proportions here - but it's worth an hour or so of exploring if you like geology and the slightly eerie feeling of being underground. The rock formations are genuinely interesting if you bother to look properly, and there's something satisfying about scrambling over stone that's been there for millennia. Children tend to find it properly thrilling, though very young ones might struggle with the uneven ground.

What makes this work brilliantly is its position within the Brecon Beacons landscape. If you're staying at Four Falls Glamping or Brecon Beacons Camping & Caravan Park, this sits nicely as a half-day venture before or after walking the ridge. Don't expect tourist facilities or guided tours - you're doing this under your own steam, which is part of its charm. Aim for a dry day because the cave can get slippery when wet. It's the sort of stop that doesn't need Instagram but sticks in your memory.