Ireby Main Sink

A sinkhole that opens into proper underground passages - that's what Ireby Main Sink amounts to near Carnforth in North Yorkshire. You're looking at a collapsed roof where water has carved through limestone, creating a vertical drop into darkness. The opening itself is dramatic enough, and if you're handy with climbing gear and know what you're doing, there's a whole cave system down there waiting. Most visitors, though, come for the sinkhole spectacle and the walk in from the road.

Cavers and geology types will find this genuinely worthwhile. It's the sort of thing that makes you understand how the landscape actually works - water doesn't just sit on top of Yorkshire's moorland, it's eating away underneath constantly. The walk to reach it is pleasant enough, rolling farmland with decent views. Allow an hour for a casual wander and a good look around.

Head here on a clear day. The light filtering into that dark throat is best when the sun's overhead. If you're based at Primrose Glamping Pods a couple of miles away, this sits nicely as a morning activity before moving on to bigger attractions in the area.

Access is free and there are no set hours - it's a natural feature sat in the landscape. That said, the ground around the actual sink is unstable in places, so watch your step. This isn't a five-minute photo stop. It demands respect and decent footwear.