St. Cuthbert's Swallet

You'll find this one on the Mendip Hills just outside Wells, and it's the kind of place that rewards a bit of scrambling. St. Cuthbert's Swallet is a natural sinkhole that drops into a cave system - the entrance is a proper vertical shaft that demands respect and a head for heights. Most visitors abseil or canyoneer through it, which means this isn't a casual stroll-in attraction. If you're into caving or outdoor adventure sports, it's genuinely worth the trip.

The geology is what draws the serious types. Water has carved limestone into a series of passages and chambers below ground, and experienced cavers can explore pools and tight squeezes depending on conditions and water levels. The swallet itself is dramatic from the rim - you can see down into the hole and feel the temperature drop. It's raw enough that you'll understand why the Mendips are considered one of Britain's best caving regions.

You'll need proper equipment and ideally experience or a guide. There's no visitor centre, no café, no hand-holding. It's a working cave system, not a show cave. That's either brilliant or completely pointless depending on what you want. Families with young kids will find it frustrating. Experienced cavers or climbers will think it's excellent.

Wells is just down the road - decent town for supplies and a bed. The camping and glamping options around here (Cheddar Camping is closest at 1.5 miles, Wells Touring Park at 2.9) are well-positioned if you're doing a caving holiday in the area. Check conditions before you go. Water levels can change everything.