Pwll y Pasg

The entrance is tucked into the hillside near Crickhowell, easy to miss if you're not looking properly. Pwll y Pasg is a proper cave system - the sort that rewards a bit of scrambling about and a torch in hand. You'll squeeze through tight passages and emerge into chambers where the silence is genuinely unsettling. Water drips from the ceiling year-round, so it's damp and slippery; trainers with grip are non-negotiable.

It's free to visit, which is brilliant, though the lack of any formal setup means you're essentially exploring on your own terms. Allow an hour if you're taking it slowly, less if you're just poking your head in. The walk from the car park is brief and straightforward. Families with older kids who don't mind a bit of confined space will enjoy it - younger children might feel claustrophobic in the narrower bits.

Walkers should time it for dry spells; after heavy rain, parts can flood. The real appeal here is doing something genuinely different from the typical park-and-stroll attractions. You're caving without the organised tour price tag. It's not Instagram-famous, which means you'll likely have the place to yourself on a midweek visit.

If you're camped at Cwmdu, it's barely twenty minutes away and makes a cracking half-day adventure. The Brecon Beacons fill the landscape around Crickhowell, so you can easily pair this with proper hill walking if you want the full Mid Wales experience.