Crescent Cave

You'll find yourself scrambling down a steep limestone slope near Brecon to reach the mouth of this modest cave - and it's genuinely worth the muddy knees. Crescent Cave isn't some vast underground cathedral; it's more of a proper Welsh working cave, with a stream running through it and the kind of atmosphere that feels genuinely wild rather than sanitised for visitors.

The cave mouth opens dramatically enough, and you can wade upstream into the darkness for a fair distance if you've got a torch and don't mind wet feet. The limestone walls glisten with moisture, and there's an almost meditative quality to picking your way through the shallow water by headtorch light. It's intimate rather than spectacular - nothing like the show caves further south - but that's precisely why it works.

Bring proper torch work and sturdy boots. An hour covers it comfortably, maybe ninety minutes if you're thorough. The free admission is brilliant; you're just crossing private land with permission. Families with older kids who don't mind getting wet will find it thrilling. Young children might find it a bit claustrophobic, if I'm honest.

If you're basing yourself at Cwmdu Campsite nearby, this slots nicely into a day of outdoor pottering around Brecon Beacons - add a walk on the hills above and you've got a proper adventure. Winter visits are atmospheric but cold; summer's more forgiving for lingering. Go early if the weather's been wet; the stream level can turn tricky.