Eglwys Faen (Main Entrance)

The entrance to Eglwys Faen sits tucked into the hillside above Crickhowell, and the moment you spot it you understand why locals call it 'the church in the stone'. It's not a church at all, of course - it's a natural cave that opens into the limestone cliffs, and the resemblance is startling enough that Victorian visitors were convinced it must be something sacred.

You're looking at one of those geological accidents that feels deliberately designed. The cave mouth gapes open with real presence, and stepping inside there's that particular coolness and quiet you only get underground. The passage runs back maybe thirty metres or so, though the exact depth depends on water levels and how far you fancy scrambling about in the dark. A torch is essential - this isn't a manicured show cave with handrails and electric lights.

Walkers get the most from it. The approach itself is scenic, with views across the Brecon Beacons from the path up, and the cave makes a proper destination rather than just a distraction. History types will enjoy the Bronze Age finds that have turned up here over the years. Young kids might find the entrance impressive but get restless if they're not confident crawlers.

It's free to visit, as far as I can tell - just local knowledge rather than a ticketed attraction. Allow an hour or so if you're doing the walk properly from Crickhowell itself. Cwmdu Campsite a few miles down is well-placed if you're basing yourself around here for a few days. The cave works best as part of a broader Brecon Beacons outing rather than a standalone stop.