Eglwys Faen (Oval Entrance)

You'll find yourself scrambling down a steep bank near Crickhowell before you spot the opening - a proper cave mouth with an oval entrance that gives the place its name. Eglwys Faen translates as 'Stone Church', and once you're inside, you understand why locals called it that. The chamber opens up unexpectedly, with natural light filtering through the entrance enough to see the rocky walls without a torch, though bringing one helps you explore deeper.

It's a short visit - most people spend twenty minutes here rather than hours - but it's the kind of stop that rewards walkers exploring the surrounding Powys countryside. The entrance scramble isn't difficult, just muddy depending on recent weather, so it suits families with older kids more than toddlers. You won't find interpretation boards or facilities; this is raw cave exploring without the visitor centre veneer.

The real appeal is geological rather than historical, despite the evocative name. If you're based at Cwmdu Campsite nearby, it makes a decent morning detour while you're tackling the walks around Crickhowell and the Black Mountains. The cave itself is free to enter - just respect the site and watch your footing on the approach.

Go if you're the type who gets excited by geology and doesn't mind a bit of scrambling for modest underground scenery. Skip it if you're after something more substantial or accessible.