Marble Sink

You'll find yourself dropping into a proper underground chamber where a stream actually vanishes into the bedrock - it's one of those geological oddities that stops you in your tracks. Marble Sink is a sinkhole cave system near Lancaster, formed where water has worn through the limestone, creating a dramatic collapse feature with a stream flowing directly into it. It's a modest spot, nothing grand like some of the show caves you'll find elsewhere in the Pennines, but that's partly why it's worth the trip.

The best bit is standing at the edge watching the water disappear into the darkness. There's something genuinely eerie about it. You can peer into the mouth of the cave itself if you're careful - the limestone formations are proper striking up close, and on a quiet afternoon you might hear nothing but the water echoing through the chamber. Geology enthusiasts will find it fascinating; the way the landscape has collapsed reveals the cave system underneath.

It's a short walk from the car park, so families with young kids can manage it without complaint, though there's not masses to do once you've had a good look and taken photos. Allow twenty minutes to half an hour. The terrain can be boggy depending on weather, so proper footwear matters. Visiting in autumn or winter when water flow is highest makes the sinkhole more dramatic.

If you're based at Orcaber Farm or Primrose Glamping Pods - both excellent stops in the area - this makes an easy morning outing before heading elsewhere. It's the sort of place that justifies a detour if you're already walking the surrounding countryside, rather than something to plan an entire day around.