Porth yr Ogof Resurgence (N)

The moment you spot water surging out of a limestone cliff face in the middle of a Welsh valley, you understand why locals call this place special. Porth yr Ogof is where an underground river - the Neath - suddenly emerges into daylight after flowing through caves you can't access from this end. It's raw geology in action, and genuinely dramatic.

You can walk right up to the resurgence point and feel the spray of cold water hitting the rocks. The cave mouth itself is sizeable but you're looking at it from outside - this isn't a through-cave walk or a guided underground tour. What you get instead is a proper sense of the landscape's hidden plumbing. The surrounding woodland is lovely for a wander, and the whole spot takes about 30-45 minutes unless you're the type to sit and sketch or photograph for hours.

Families with older kids will find it engaging; younger ones might get bored quickly since there's no path into the cave itself. Serious cavers and geology enthusiasts will want this on their list. It's free and there's nowhere official to pay anyway.

Neath is your nearest town, but honestly you'd base yourself at Four Falls Glamping just down the road - it's well positioned for this and the broader Brecon Beacons valleys. The resurgence fits neatly into a half-day exploring the Neath valley's cave systems and waterfalls. Go when the river's running high after rain; in dry summers it's less impressive.