See the UK from a different angle by going down and getting muddy in these awesome potholing spots.
Hidden under the crust of the United Kingdom is a subterranean realm of dark tunnels and incredible caverns. Here are ten of the best ones.

1.    Alum Pot, Yorkshire
A forgotten world that few people will see, the Alum Pot is an 80m open shaft. To get there, Lost Earth Adventures will lead you on a trip through the Long Churns underwater stream and down the Dolly Tub descent. In the sunlit cavern itself, you will descend and cross the middle to 'The Bridge.'
Level: Suitable for beginners.
 

2.    Gaping Gill, Yorkshire
One of the longest cave systems in the United Kingdom, Gaping Gill's massive main chamber is 129m long and 31m wide. The first descent was made in 1865 by Edouard Martel, who used the telephone to communicate to the surface team. You will make the same descent today using a winch run by the Bradford and Craven Pothole Clubs. You can only use the machine twice a year, but you can book it in your diary.
Level: Suitable for beginners.

 
3.    The Easegill system, Yorkshire
The biggest cave system in Britain straddles three counties and has more than 40 miles of passageways. With many entrances, the 33m drop at Lancaster Hole is one of the most common. Nearby is a series of floor-to-ceiling columns – in the 1960s, one column was climbed, destroyed, and rebuilt with glue. Entry to most places is only by permit, so you'll need to prepare accordingly.
Level: Best for experienced cavers

 
4.    OgofFfynnonDdu, South Wales
The 'Cave of the Black Spring' is the deepest and third longest cave in Britain, 300 metres deep. Navigation is famously challenging, with 30 miles of windy passageways, waterfalls and potholes. Few bits are immersed in water, so you're going to hold your breath in places.
Level: Best for experienced caverns and clubs.

 
5.    OgofDraenen, South Wales
'Hawthorn Cave' has more than 40 miles of passageways, making it the longest cave system in Wales. This massive complex contains fantastic mineral deposits decorating vast caverns like the 'Battle of the Worlds.'
Level: Experienced caverns that belong to caving clubs.

6.    PorthyrOgof, South Wales
Set in the south of Brecon Beacons, PorthyrOgof has the largest cave entrance in Wales, more than 17m wide and 5m tall. With a lot of route choices for all skills, first-timers will follow a map to the simplest areas, while experienced caverns have narrow stairs, bumps and a labyrinth of passageways to solve.
Level: All abilities, including kids.

 
7.    Clearwell Caves, Gloucestershire
One for families and the first timers, this natural cave system has been mined for iron ore and ochre for thousands of years. All skills can take a deep-level cave experience, descending 60 metres underground to crawl, walk and scramble along the passageways.
Level: All levels, including beginners and kids.

 
8.    Swildon's Hole, Somerset
Beneath the Mendip Hills lies Britain's largest underground river system and a massive network of caves. The first cave diving attempt in the UK took place here at Swildon's Hole in 1934. All abilities will navigate this cave, with novices starting in the upper passages before climbing, pressing and swamping (underwater sections) in the main stream.
Level: All abilities, including beginners.

9.    Giant’s Hole, Peak District
Narrow tunnels, thirty-feet drops, roaring waterfalls and unusual rock formations: welcome to Giant's Pit. A stream flows through the gateway, leading to a series of sumps. Some sections are ideal for novices, but the best pieces lie within Garland's Pot – a 7m plunge that leads to complicated passageways and technical caving.
Level: All skills, including beginners; (with a guide).

 
10.    Fingal's Cave, Inner Hebrides
A sea cave located on the uninhabited Scottish island of Staffa, Fingal's is made up entirely of hexagonal columns of basalt. The arched roof inside creates a cathedral-like acoustics. You can explore through a walkway that leads over a high water table. It was beingcalled by Walter "...one of the most extraordinary places I've ever seen."
Level: All abilities, including kids.