This is not just a walk but something for those who like a bit of adventure & are not afraid of heights & drops & are not to heavy plus it's a response to Pauls "everyone walks up Ingleborough from Clapham". Ok I'll admit I did partly and the GPX plot shows where I went to partly but even this sites 3D mapping & probably every GPS unit would then fail as upon reaching my target on the surface I went down Englands highest single drop fall of 98m (322ft). Hopefully I've got you intrigued now.
Well the answer is Gaping Gill as around now back in 2008, I walked up from Clapham with Mother to the entrance, as on one of the 2 bank holiday weekends days per year there is a winch set up by caving clubs to let the public descend. The main stream is diverted down an alternate entrance hole & a bosun's chair set up to winch you down.
As shown in the pics you walk the plank literally over the drop, admittedly there is scaffolding to support it, you sit in the chair and are clamped in then, they then ask you to lift your legs & they slide the floor out from under you and all you can see looking down is blackness, you're told to keep arms in & head up so you don't scrape the side, although you are going down on a guide wire to angle you away from the water & sides and prevent sway.
Once at the bottom you can get out and wander round the main chamber which had some very limited illumination set up and once you've had enough you ask the man at the bottom nicely that'd you'd like to go up. & since I'm writing this you know I asked nicely
GPX Plot of Route - there & back
Pics 1&2 The scafolding & plank
Pic 3 - A Great Big Hole
A whole load of pics from at the bottom
Pic 13 - The Cavers Encampment
Pic 14- People waiting there turn
Pic 16 & 17 - Walking back down through the collapsed cave
Pic 18 - The Gorge Opens Out
Pic 19 - Looking back
ps If you ever do it you'll understand trying to get quality pics with a hand held compact camera is hard, just don't use flash or you'll get nothing but illuminated water drops.