0:00:03 > 0:00:06I'm Richard Parks, former Welsh rugby international
0:00:06 > 0:00:09turned professional endurance athlete.
0:00:09 > 0:00:11And I push my body to the limit
0:00:11 > 0:00:15in some of the world's most extreme and remote environments,
0:00:15 > 0:00:18yet one thing I've learnt
0:00:18 > 0:00:21is that some of the best adventures can be had right here in Wales,
0:00:21 > 0:00:22on my doorstep.
0:00:24 > 0:00:26Or should I say... underneath my doorstep.
0:00:30 > 0:00:33Welcome to my big Welsh adventure.
0:00:35 > 0:00:392016 is the Welsh Year Of Adventure, and to celebrate it
0:00:39 > 0:00:42I've set myself three very different adventure challenges.
0:00:44 > 0:00:48Cycling south to north through the glorious Welsh mountains,
0:00:48 > 0:00:51creating a new cycle route, the highest in Wales.
0:00:52 > 0:00:55I'm following the River Teifi from source to sea,
0:00:55 > 0:00:59running and kayaking on one of the longest rivers in the country.
0:01:00 > 0:01:02This time I'm going underground,
0:01:02 > 0:01:05caving in the Brecon Beacons on a mega mission that will
0:01:05 > 0:01:09take me to the deepest point of the deepest cave system in the UK.
0:01:13 > 0:01:15BLEEP
0:01:25 > 0:01:29What lies underground is of huge significance to Wales
0:01:29 > 0:01:30and its people.
0:01:30 > 0:01:33This is Cwm Du, an open cast limestone quarry
0:01:33 > 0:01:36in the Brecon Beacons National Park.
0:01:36 > 0:01:38It was mined for hundreds of years.
0:01:38 > 0:01:43At the industry's peak, 14.5 million tonnes of limestone per year
0:01:43 > 0:01:47was extracted and exported from quarries like this one.
0:01:48 > 0:01:51Vast scars on the landscape tell the story of how
0:01:51 > 0:01:55Welsh people once depended on this, their country's mineral wealth.
0:01:56 > 0:02:00Today the industry here is a thing of the past, but thanks to
0:02:00 > 0:02:04its remarkable geology, these rocks are still very much in use.
0:02:04 > 0:02:08Beneath me is an incredible system of limestone caves.
0:02:08 > 0:02:11Their creation began 300 million years ago
0:02:11 > 0:02:15when all this was a tropical seabed thousands of miles south of here.
0:02:15 > 0:02:17As the tectonic plates collided,
0:02:17 > 0:02:20these ancient seabeds were shunted north.
0:02:20 > 0:02:24Huge pressures buckled the rock, thrusting it to the surface,
0:02:24 > 0:02:26creating the Welsh landscape we see today.
0:02:27 > 0:02:31All around me are telltale signs of the limestone world
0:02:31 > 0:02:33I'm about to enter, home to caves
0:02:33 > 0:02:37but also to rare and beautiful alkaline-loving plants
0:02:37 > 0:02:40like this, Riddelsdell's hawkweed.
0:02:40 > 0:02:43It may look like a common-or-garden dandelion,
0:02:43 > 0:02:45but this species is one of the special ones.
0:02:46 > 0:02:51According to Natural Resources Wales, who manage this reserve,
0:02:51 > 0:02:54there are some species of hawkweed, like that little fella up there,
0:02:54 > 0:02:58that are so rare, they are only found here in this quarry.
0:02:59 > 0:03:02But the ground beneath this quarry
0:03:02 > 0:03:04is where I'm heading for the next two days.
0:03:04 > 0:03:08I'm not going to lie, I'm a little nervous about this challenge.
0:03:08 > 0:03:10I'd much rather be climbing a mountain
0:03:10 > 0:03:12than going deep underground.
0:03:15 > 0:03:18There are over 1000 caving sites in Wales
0:03:18 > 0:03:20and this is an exceptional example.
0:03:20 > 0:03:25The Ogof Ffynnon Ddu cave system, or OFD for short, is the deepest cave,
0:03:25 > 0:03:28not only in Wales but in the UK.
0:03:28 > 0:03:31It runs through the mountains in the west of the Brecon Beacons.
0:03:31 > 0:03:33This is a two-day adventure.
0:03:33 > 0:03:36Day one - I'll explore the top section of the cave,
0:03:36 > 0:03:40a maze of tunnels and passages with spectacular rock formations.
0:03:40 > 0:03:45Day two - I'm on a 15-hour mission starting at the cave's top entrance
0:03:45 > 0:03:49and dropping over 900ft to the lowest point in the system.
0:03:49 > 0:03:52I'm meeting Gary Evans from the South Wales Caving Club
0:03:52 > 0:03:54and Mid Wales Cave Rescue Team,
0:03:54 > 0:03:57who's going to be with me as I explore underground.
0:04:00 > 0:04:02Richard. Hi, Gary. How are you doing? Good to meet you.
0:04:02 > 0:04:05Really good, thanks. How are you? Good, thank you.
0:04:05 > 0:04:06Looking forward to this?
0:04:06 > 0:04:07HE LAUGHS
0:04:07 > 0:04:10I've got mixed feelings about it if I'm being honest! Yeah?
0:04:10 > 0:04:11I'm a little apprehensive about it.
0:04:11 > 0:04:15I'm not a massive fan of confined spaces. OK. I'd say I'm...
0:04:16 > 0:04:19..60% excited, 40% nervous.
0:04:19 > 0:04:22Well, I think you'll be pleasantly surprised. It's real big in here.
0:04:22 > 0:04:25It's a bit deceiving, isn't it? It is, it looks quite ominous.
0:04:25 > 0:04:26Yeah, so it's got a gate on it
0:04:26 > 0:04:28and that's really for a couple of reasons.
0:04:28 > 0:04:31It conserves the caves and also, from a safety point of view,
0:04:31 > 0:04:35it means you haven't got people wandering around in there, getting lost,
0:04:35 > 0:04:37so it's a small entrance protecting over 60km of passage.
0:04:37 > 0:04:40'Gary's kitting me out with essential safety gear,
0:04:40 > 0:04:43'a caving belt used as a harness and a helmet.'
0:04:43 > 0:04:46I feel like it accentuates my hips as well!
0:04:46 > 0:04:50'As I feared, it's not going to be a walk in the park.'
0:04:50 > 0:04:52We've got our baggage as well. Yeah.
0:04:52 > 0:04:55So we've got some safety gear and some other bits of equipment.
0:04:55 > 0:04:58I guess we could make our way underground when you're ready.
0:05:00 > 0:05:01OK, Richard.
0:05:03 > 0:05:06'Within just a few seconds we are plunged from bright sunlight
0:05:06 > 0:05:08'into total darkness.
0:05:08 > 0:05:12'All I can hear is the distant drips through an eerie silence.
0:05:14 > 0:05:17'You'd expect it to be cold in here but it's not.
0:05:17 > 0:05:20'In fact, this cave has a year-round ambient temperature
0:05:20 > 0:05:22'of 12 degrees Celsius.'
0:05:22 > 0:05:25We're just going to have a little sit down just here.
0:05:25 > 0:05:27Have a seat there.
0:05:29 > 0:05:32So we're in the cave, so we're just going to turn our lights off
0:05:32 > 0:05:34for a few moments, let our eyes adjust,
0:05:34 > 0:05:37and we'll sit here in the dark for a couple of minutes.
0:05:38 > 0:05:40Wow. So that's pitch-black.
0:05:42 > 0:05:45It's a very primal darkness, isn't it?
0:05:45 > 0:05:48Yeah. It's darkness unlike...
0:05:48 > 0:05:51you know, you'd experience in the normal world
0:05:51 > 0:05:53cos there's always light pollution of some sort.
0:05:53 > 0:05:56I'm looking at you but I have no idea if you're looking at me.
0:05:56 > 0:05:58Are you looking at me? Are you still there? I am, yeah!
0:05:58 > 0:06:01I can hear your voice. I feel I should look that way,
0:06:01 > 0:06:02but you're right, it's pitch-black
0:06:02 > 0:06:05and because there's no light, our eyes just can't adjust to it,
0:06:05 > 0:06:08so what's happening is our pupils are dilating,
0:06:08 > 0:06:10trying to find light so by turning our lights off,
0:06:10 > 0:06:12it allows our pupils to dilate,
0:06:12 > 0:06:14looking for whatever light they can find,
0:06:14 > 0:06:16which means we're going to see much better
0:06:16 > 0:06:19when we turn our lights on again in a moment. Sure.
0:06:19 > 0:06:20So if you're ready... Yeah.
0:06:20 > 0:06:24..we can pop our lights on and make some progress.
0:06:24 > 0:06:25All set?
0:06:25 > 0:06:26You still there?
0:06:26 > 0:06:27THEY LAUGH
0:06:27 > 0:06:29Come on, then.
0:06:29 > 0:06:31'It's incredibly hazardous going,
0:06:31 > 0:06:34'which I'm used to as an experienced mountaineer,
0:06:34 > 0:06:37'but this is all new for me. I've never been caving before.
0:06:37 > 0:06:39'Normally I can see where I'm stepping.'
0:06:39 > 0:06:42Just take your time, watch where you're putting your feet.
0:06:42 > 0:06:44Gary, I can hear the drips. Yeah.
0:06:46 > 0:06:49Is it water that created these caves? Yeah, it was.
0:06:49 > 0:06:51It's amazing to think, isn't it,
0:06:51 > 0:06:54all these huge passageways formed just by water action?
0:06:54 > 0:06:57It rains and that rain falls through the air, picks up carbon dioxide,
0:06:57 > 0:07:00picks up more carbon dioxide in the soil,
0:07:00 > 0:07:02which forms a weak acid called carbonic acid,
0:07:02 > 0:07:06and when that comes into contact with the limestone, it dissolves it
0:07:06 > 0:07:08and it's that that starts to form the passageways.
0:07:08 > 0:07:10If you look at into the roof,
0:07:10 > 0:07:13you can see right up there is where the passages first formed.
0:07:13 > 0:07:16What surprises people is that the oldest part is the highest part
0:07:16 > 0:07:20and we're in the newest part. That's fascinating, fascinating.
0:07:20 > 0:07:22Shall we crack on? Yeah, great. Yeah.
0:07:24 > 0:07:28'One of the first rules of caving is never enter a cave alone,
0:07:28 > 0:07:30'and I'm just beginning to see why.'
0:07:30 > 0:07:32It's like a labyrinth in here.
0:07:32 > 0:07:38I can imagine it's pretty easy to get disorientated and even lost
0:07:38 > 0:07:42so, just like above ground, I'd use a map to navigate,
0:07:42 > 0:07:45I've got a map here, but cavers refer to them as surveys.
0:07:47 > 0:07:50Gary wants to see how I'd cope if he were injured
0:07:50 > 0:07:52or if I found myself alone.
0:07:52 > 0:07:56In an exercise experienced cavers practise, he's asked me to navigate
0:07:56 > 0:08:01through a maze of tunnels towards a chamber called Gnome Passage.
0:08:01 > 0:08:04So where we're standing, there's seven ways on from here.
0:08:04 > 0:08:09There's a couple of ways behind, there's a way up here... Yeah.
0:08:09 > 0:08:11There's a way going that way...
0:08:11 > 0:08:13Yeah. And then there's three more below us,
0:08:13 > 0:08:17so you need to make a choice now and get us on track.
0:08:17 > 0:08:18'Even with my survey,
0:08:18 > 0:08:21'this is totally different from navigating above ground.
0:08:21 > 0:08:25'This is an alien world and I'm not used to reading the rocks,
0:08:25 > 0:08:28'so to me every option looks pretty much the same.'
0:08:28 > 0:08:33I would say we go ahead and take the left passage over there.
0:08:33 > 0:08:34OK. You confident?
0:08:34 > 0:08:36Always. Come on, then. Let's have a look.
0:08:41 > 0:08:44'As we head off, we find more passages with different route options.
0:08:45 > 0:08:51'I soon realise how easily you can become disorientated in here.'
0:08:51 > 0:08:53OK. I think...
0:08:55 > 0:08:57..that we're there. Which means that...
0:08:59 > 0:09:01..it's straight on and to the left.
0:09:01 > 0:09:04You must have some stories of people getting lost down here.
0:09:04 > 0:09:07A couple of years ago we had a, I think, 12-15-hour search.
0:09:07 > 0:09:09We just didn't know where they were in the system,
0:09:09 > 0:09:12so we had to put a number of search teams in.
0:09:12 > 0:09:14Now's not the time for horror stories, I guess.
0:09:14 > 0:09:17Well, you're doing really well so far, so let's just keep that going.
0:09:17 > 0:09:18Cheers, mate. All right.
0:09:20 > 0:09:24'We're only 200ft horizontally into the cave.
0:09:24 > 0:09:27'I'm navigating in this pitch-black labyrinth with only
0:09:27 > 0:09:29'our head torches to light the way.'
0:09:30 > 0:09:34On the right is a little side passage we didn't take. Don't tell me, don't tell me.
0:09:38 > 0:09:39GARY WHISTLES
0:09:39 > 0:09:43Have I gone the wrong way? You have. Ah.
0:09:43 > 0:09:46Ah, well. That's a really common junction for mistakes there.
0:09:46 > 0:09:48People take the wrong turning.
0:09:48 > 0:09:52'Gary takes control of the navigation again, but this exercise
0:09:52 > 0:09:55'has certainly given me confidence if we were to be separated.
0:09:55 > 0:10:00'I'm now able to focus on the raw beauty of the environment around me.'
0:10:02 > 0:10:05Tell the story behind some of the colours that we can see.
0:10:05 > 0:10:07It's quite interesting. It's complex, really.
0:10:07 > 0:10:09We're seeing a lot of different things.
0:10:09 > 0:10:11Some of it is the calcite on the walls,
0:10:11 > 0:10:14that's that white you're seeing on the wall there, and also all
0:10:14 > 0:10:18the mud colour, the sandy colour, that's caused by glaciation, really.
0:10:18 > 0:10:20All of the material they dragged across the surface
0:10:20 > 0:10:23has come in with the meltwater and flooded into the cave
0:10:23 > 0:10:26and that's all the mud on the floor and on the walls that we're seeing.
0:10:26 > 0:10:28'This cave was first discovered in 1946
0:10:28 > 0:10:31'and there are still parts of this system
0:10:31 > 0:10:35'where fewer people have stood than on the surface of the moon.
0:10:35 > 0:10:38'In fact, caves are the only places
0:10:38 > 0:10:42'left in the UK where genuine new exploration still occurs.
0:10:42 > 0:10:45'The OFD is a Site of Special Scientific Interest and
0:10:45 > 0:10:47'its contents are closely guarded.
0:10:47 > 0:10:49'I've arranged to meet Alan Bowring,
0:10:49 > 0:10:53'a geologist from the Brecon Beacons National Park Authority,
0:10:53 > 0:10:57'and Claire Vivian, a cave warden with a special interest in conservation,
0:10:57 > 0:11:00'who are going to tell me more about their work.'
0:11:00 > 0:11:04I've learned from Gary that there are sections of this cave
0:11:04 > 0:11:07that, you know, are like time capsules from millions of years ago.
0:11:07 > 0:11:09Yes, definitely. That's very true.
0:11:09 > 0:11:13There are a lot of very fragile formations here as well.
0:11:13 > 0:11:16You know, one careless boot in the wrong place could
0:11:16 > 0:11:20destroy something that has been busy growing for thousands of years.
0:11:20 > 0:11:24'They are conserving calcite pools created by puddles of water
0:11:24 > 0:11:28'which have filled and drained over hundreds of thousands of years.'
0:11:28 > 0:11:30All of this rock is made of calcite
0:11:30 > 0:11:32but we're seeing it in a crystalline form here,
0:11:32 > 0:11:35all of which are slightly different.
0:11:35 > 0:11:37There are some wonderful ones further down Gnome Passage.
0:11:37 > 0:11:40'We're actually very close to the entrance of Gnome Passage.
0:11:40 > 0:11:43'It's one of the cave's most impressive features
0:11:43 > 0:11:44'and Alan tells me
0:11:44 > 0:11:48'I need something more powerful than a few head torches to see it.'
0:11:49 > 0:11:51Wow.
0:11:51 > 0:11:53It's quite something, isn't it?
0:11:53 > 0:11:56The famous Gnome Passage.
0:11:56 > 0:11:57HE LAUGHS
0:11:57 > 0:11:58That's massive!
0:12:00 > 0:12:02I wasn't expecting it to be that big.
0:12:02 > 0:12:05It's hard to articulate but you could easily fit the body of
0:12:05 > 0:12:10a jumbo jet in there. Oh, you could use the whole plane. Yeah.
0:12:10 > 0:12:14'This magnificent chamber is at points 30ft wide,
0:12:14 > 0:12:18'30ft high and an incredible 260ft long.'
0:12:19 > 0:12:23Alan, I can see why it's called Gnome Passage now!
0:12:24 > 0:12:27'Before my eyes, hundreds of stalagmites.
0:12:30 > 0:12:34'Huddled together, the cave version of lonely garden gnomes.'
0:12:36 > 0:12:38That's...
0:12:38 > 0:12:40That's an incredible feature.
0:12:40 > 0:12:41It looks like wax, doesn't it?
0:12:41 > 0:12:45Dripped over the rock. That's exactly what it looks like, yeah.
0:12:45 > 0:12:47How does water actually create that?
0:12:47 > 0:12:49The water picks up carbon dioxide.
0:12:49 > 0:12:54It becomes a very weak acid and what that can do is dissolve limestone,
0:12:54 > 0:12:57so it carries the limestone in solution and
0:12:57 > 0:12:58when it gets to a place like this,
0:12:58 > 0:13:02it releases a little bit of that calcium carbonate as calcite
0:13:02 > 0:13:07but if you've got drip after drip after drip over a long, long period,
0:13:07 > 0:13:08that's what you end up with.
0:13:08 > 0:13:12How many years are we talking here? Like, roughly, I mean...
0:13:12 > 0:13:15Well, if you can imagine a millimetre of this material
0:13:15 > 0:13:19being added every ten years... OK.
0:13:19 > 0:13:23It's a long, long time. Thousands, hundreds of thousands of years.
0:13:23 > 0:13:25We could stand here for our whole lifetimes
0:13:25 > 0:13:27and we wouldn't see much change.
0:13:27 > 0:13:30'There's plenty to see on the floor of the cave,
0:13:30 > 0:13:35'but when I look up there are equally stunning stalactites.'
0:13:35 > 0:13:39It's so cool to be so close to them
0:13:39 > 0:13:41and to be able to see the detail so clearly.
0:13:41 > 0:13:45It looks like fabric flowing, doesn't it? Yeah, or streaky bacon.
0:13:45 > 0:13:47RICHARD LAUGHS
0:13:47 > 0:13:49I like... Can you see that? I can, I can.
0:13:49 > 0:13:52And this tiny stalactite there,
0:13:52 > 0:13:55it goes from sort of an amber into a dark brown
0:13:55 > 0:13:59into a white and the tip is clear.
0:13:59 > 0:14:04The clear tip is pretty much pure calcite and the darker colours,
0:14:04 > 0:14:10those rich oranges, ambers, you say, or brown, that's iron.
0:14:10 > 0:14:14'My eyes have been truly opened to this subterranean world.
0:14:14 > 0:14:17'Natural beauty slowly forming here
0:14:17 > 0:14:20'in the darkness for hundreds of thousands of years.
0:14:22 > 0:14:25'I've been exploring underground for nine hours now.
0:14:25 > 0:14:28'This cave is a conservation area, so no camping.
0:14:28 > 0:14:32'We have no choice but to retrace our steps back to the entrance.
0:14:36 > 0:14:39'It's day two and I'm still caving with Gary and Claire.
0:14:40 > 0:14:44'Today I'm dropping over 900ft from the top entrance
0:14:44 > 0:14:46'to the deepest point of the cave.
0:14:46 > 0:14:50'Once in the system, there's no way to communicate with the surface,
0:14:50 > 0:14:53'so we have to put a time limit on the trip.
0:14:53 > 0:14:55'Experienced cavers take five hours
0:14:55 > 0:14:57'to complete this demanding challenge.
0:14:57 > 0:15:02'With a film crew and kit in tow, it will take us considerably longer.
0:15:02 > 0:15:06'Within 15 hours we must re-emerge and call in to avoid a rescue.
0:15:08 > 0:15:11On my way, I'll have to twist through the Corkscrew,
0:15:11 > 0:15:14belay down Maypole Inlet
0:15:14 > 0:15:16and travel through the streamways.
0:15:16 > 0:15:18I'll have to climb the Diver's Pitch
0:15:18 > 0:15:20then crawl through the Letterbox,
0:15:20 > 0:15:23finally arriving at the bottom of Gothic Passage,
0:15:23 > 0:15:25the end of my journey.
0:15:25 > 0:15:27Let's do this.
0:15:29 > 0:15:32'This giant hole was formed by an ancient river
0:15:32 > 0:15:35'that once filled this chamber.
0:15:35 > 0:15:38'As the water cut through the rock, it left this huge crevasse.'
0:15:43 > 0:15:46Hi, Claire. Hi, Richard.
0:15:46 > 0:15:50'Very quickly, we reach the first of many narrow sections.
0:15:50 > 0:15:52'This one is known as the Corkscrew.'
0:15:52 > 0:15:56You might be laughing now, being so small... Oh, I know, I know.
0:15:56 > 0:15:59But I'm sure my long legs are going to come in handy at some point.
0:16:06 > 0:16:08I can see why this is called the Corkscrew now.
0:16:10 > 0:16:13There's just not a bottle of wine at the end of it!
0:16:15 > 0:16:18'I'm 6'2", so I'm having to twist and contort my body
0:16:18 > 0:16:21'in order to push myself through these tiny gaps.'
0:16:23 > 0:16:25This seemed like a good idea at the time.
0:16:25 > 0:16:26CLAIRE LAUGHS
0:16:26 > 0:16:27Famous last words.
0:16:38 > 0:16:42'I've literally popped out of The Corkscrew and can stand up again.
0:16:42 > 0:16:46'I soon realise that the nature of the cave has changed dramatically.
0:16:46 > 0:16:49'We have transitioned from dry to wet caving.'
0:16:49 > 0:16:51WATER FLOWS
0:16:51 > 0:16:55You know, we've come into a really different part of the cave now,
0:16:55 > 0:16:58haven't we? It feels really different. I can hear the water.
0:16:58 > 0:17:02We've got something interesting to show you just here on the right.
0:17:02 > 0:17:04This is a gastropod.
0:17:04 > 0:17:06To think that that would have been
0:17:06 > 0:17:11living on the seabed around 330 million years ago is incredible.
0:17:13 > 0:17:17'In fact, these limestone caves are almost completely made of
0:17:17 > 0:17:19'crushed sea creatures and corals.'
0:17:21 > 0:17:22That's really cool. Yeah.
0:17:22 > 0:17:26Fossils and all. Loads of fossils.
0:17:26 > 0:17:29Is that why you love this place so much, why you love caving so much?
0:17:29 > 0:17:33For me, it's a big adventure, but it's also incredibly pretty,
0:17:33 > 0:17:38incredibly beautiful, and the sights you see here, few people will see.
0:17:38 > 0:17:41It's a bit like, you know, when I'm on an expedition
0:17:41 > 0:17:43or when I'm climbing, you forget to take it in
0:17:43 > 0:17:46and just, there's so much going on in here, isn't there?
0:17:46 > 0:17:48Oh, yes, it's absolutely amazing.
0:17:48 > 0:17:52If you just stomp through quickly, you miss a lot of what's going on.
0:17:52 > 0:17:55Oh, yeah. So just taking a moment to pause, have a look up,
0:17:55 > 0:17:59have a look around you, get the whole experience, is well worth it.
0:18:00 > 0:18:04'Wales is equally amazing underground as it is above ground.
0:18:04 > 0:18:08'There's a myriad of changing landscapes and each one comes
0:18:08 > 0:18:12'with different physical challenges. Caving is a total body workout.'
0:18:43 > 0:18:45RICHARD LAUGHS
0:18:45 > 0:18:48I'm laughing because...
0:18:48 > 0:18:50I guess it's either laugh or, uh...
0:18:51 > 0:18:55..or start to freak out because I actually can't turn my head around.
0:18:59 > 0:19:01My... Yeah.
0:19:03 > 0:19:05'This is Maypole Inlet.
0:19:05 > 0:19:07'It's a narrow gully
0:19:07 > 0:19:10'that spirals and drops 36ft to a small stream
0:19:10 > 0:19:13'that eventually joins the main streamway.'
0:19:13 > 0:19:16Now, this is what I imagined caving would be like.
0:19:19 > 0:19:22'It's a technical beast and hard to climb down.
0:19:22 > 0:19:26'I can't stop thinking that it would be even harder to climb back up.
0:19:28 > 0:19:31'I have the feeling that from here there's no turning back.'
0:19:43 > 0:19:46'Right now I'm glad that Gary's on the end of my belay.'
0:19:48 > 0:19:50Can I get a small slack, please, Gary?
0:19:55 > 0:19:57Thank you.
0:19:57 > 0:20:01'We've now travelled nearly 300ft on the vertical range
0:20:01 > 0:20:03'down from the entrance.'
0:20:03 > 0:20:06Well, I've...
0:20:06 > 0:20:08I've never been this far underground.
0:20:08 > 0:20:11This is a really significant adventure.
0:20:11 > 0:20:14I didn't know what to expect. I...
0:20:14 > 0:20:19I'm not a massive fan of confined spaces but the challenge is...
0:20:21 > 0:20:24..sort of controlling the inner dialogue in your mind.
0:20:26 > 0:20:28When you really think that...
0:20:30 > 0:20:36..you know, we're deep underground here and we're going deeper,
0:20:36 > 0:20:39the boy in me is just thinking,
0:20:39 > 0:20:42what monster's going to be round the next corner?
0:20:42 > 0:20:45And that monster is called the lower streamway.
0:20:45 > 0:20:48This starts with a climb down a waterfall
0:20:48 > 0:20:51followed by a long traverse dropping ever deeper,
0:20:51 > 0:20:52all along an underground river.
0:20:59 > 0:21:02'I'm roped up on this climb. Being so far underground,
0:21:02 > 0:21:06'if I was to fall, it would be almost impossible to get me out.'
0:21:16 > 0:21:18OK!
0:21:21 > 0:21:24'If the water is dangerously high when we get to the river
0:21:24 > 0:21:27'at the bottom, we won't be able to pass through it,
0:21:27 > 0:21:31'halting our mission to climb down to the deepest part of the cave.
0:21:31 > 0:21:33'Gary will make the final decision.'
0:21:33 > 0:21:35Feet down and step into here, mate. Yeah.
0:21:39 > 0:21:43This is a really key part of our adventure as we've dropped
0:21:43 > 0:21:44into the lowest waterway.
0:21:44 > 0:21:46And as you can imagine, if water levels were high,
0:21:46 > 0:21:48this would be a really dangerous part.
0:21:48 > 0:21:51We'd have had to turn around and climb all the way back up that
0:21:51 > 0:21:53and out that way, but I'm in good hands,
0:21:53 > 0:21:55Gary's happy with the water levels,
0:21:55 > 0:21:58we've been blessed with a few good days of weather above ground.
0:21:58 > 0:22:01We can keep going anyway, that's the good bit.
0:22:01 > 0:22:04'There's a lot of water around me.
0:22:04 > 0:22:07'If the level is above your boots, that means that further downstream
0:22:07 > 0:22:11'the passage is flooded and too dangerous to navigate.
0:22:11 > 0:22:15'This is a bigger and more visceral adventure than I ever imagined.
0:22:16 > 0:22:18'The noise is deafening.
0:22:18 > 0:22:21'We're all soaking wet and fatigue is taking hold.
0:22:23 > 0:22:27'We now really are at the mercy of what's going on above ground.
0:22:27 > 0:22:29'Welsh weather can change in an instant.'
0:22:35 > 0:22:39That's water from an inlet being fed from the surface and
0:22:39 > 0:22:43it's one of the few connections that we have with the world above us,
0:22:43 > 0:22:46and the fact that that's flowing so heavily
0:22:46 > 0:22:49means that it's almost definitely raining above ground now.
0:23:02 > 0:23:04'As we move further into the streamway,
0:23:04 > 0:23:08'I'm met by swirling pools of chest-deep, fast-flowing water.
0:23:08 > 0:23:12'I have to do some serious clambering over the wet rock.
0:23:12 > 0:23:15'But it's the water flowing over this rock that is responsible for
0:23:15 > 0:23:17'the fantastic spectacle ahead.'
0:23:18 > 0:23:23I feel like we're in another really distinctive part of the cave now.
0:23:23 > 0:23:26You're right. This is called Marble Showers, all of this,
0:23:26 > 0:23:28and here's the showers. Yeah!
0:23:28 > 0:23:30And here's the marble effect. Yeah.
0:23:30 > 0:23:35And this, the white striations we're seeing, that's the same calcite
0:23:35 > 0:23:37as in the stalagmites and stalactites.
0:23:37 > 0:23:40Formed in a slightly different way because all of the calcite
0:23:40 > 0:23:45we're seeing is populating what were cracks. OK.
0:23:45 > 0:23:47So what you had were cracks that had been formed
0:23:47 > 0:23:49by some kind of stress fracture.
0:23:49 > 0:23:53The calcite has crystallised into the cracks
0:23:53 > 0:23:57and we're seeing the cracks now full of calcite. They're beautiful.
0:23:57 > 0:23:59They really are, aren't they?
0:23:59 > 0:24:03'I've been wet for the best part of five hours now.
0:24:03 > 0:24:07'Luckily, I'm heading towards a drier part of the cave.'
0:24:10 > 0:24:16We've just climbed out of the main streamway and now into
0:24:16 > 0:24:19the dry section of the caves.
0:24:22 > 0:24:25Having been wet for the last few hours, it's...
0:24:25 > 0:24:27it's good to get in the dry part,
0:24:27 > 0:24:30but the next section is called Diver's Pitch and...
0:24:33 > 0:24:37..it's quite an infamous part of this route.
0:24:37 > 0:24:39It's going to be a tight squeeze.
0:24:41 > 0:24:45'However, the rainfall above means that it doesn't stay dry for long,
0:24:45 > 0:24:49'and within minutes once again I'm drenched.'
0:24:53 > 0:24:54Climbing!
0:24:57 > 0:24:59'This is Diver's Pitch,
0:24:59 > 0:25:03'a waterfall that cascades off a 40ft sheer cliff face.
0:25:03 > 0:25:07'I'm used to climbing but I'm going to have to concentrate on this one.'
0:25:21 > 0:25:24I thought this was supposed to be a dry part of the cave.
0:25:24 > 0:25:27HE LAUGHS
0:25:29 > 0:25:30'This is full-on.
0:25:34 > 0:25:37'After my climb, I go straight into
0:25:37 > 0:25:41'what cavers technically call a squeeze - and now I know why.'
0:25:41 > 0:25:43Mate, do I get rid of this BLEEP bag?
0:25:44 > 0:25:46Let me see if I can put it behind me.
0:25:47 > 0:25:49Uh...
0:25:49 > 0:25:51Oh, BLEEP!
0:25:51 > 0:25:53'And as I've mentioned before,
0:25:53 > 0:25:55'I'm not the biggest fan of tight spaces.'
0:25:56 > 0:25:59BLEEP
0:26:00 > 0:26:02'It's tough going. Really exhausting work.'
0:26:04 > 0:26:05BLEEP
0:26:05 > 0:26:08'And I'm constantly battling to control my growing anxiety.'
0:26:19 > 0:26:21BLEEP I've got to get out of that BLEEP.
0:26:23 > 0:26:26'Thankfully, I'm nearly at the end of this crawl.
0:26:26 > 0:26:27'One final push and I'm through.'
0:26:27 > 0:26:30Oh, my God, I can't believe I came through that.
0:26:32 > 0:26:35Put your feet right... Wow.
0:26:35 > 0:26:38This is actually pretty cool. Yeah.
0:26:39 > 0:26:42You wouldn't want to come out here and have a fall, though, would you?
0:26:42 > 0:26:46Oh, no. It's a long way down. It's definitely a tricky one.
0:26:46 > 0:26:48OK. Thanks, mate.
0:26:49 > 0:26:52Thank you. From the top they can get flaky.
0:26:52 > 0:26:54They look a bit dodgy, don't they? Yeah.
0:26:58 > 0:27:01'The journey from here continues to get tougher.'
0:27:01 > 0:27:04Still ahead are a series of climbs, squeezes,
0:27:04 > 0:27:09waterways and passages descending the final 200ft.
0:27:09 > 0:27:11We have to push on.
0:27:11 > 0:27:14We only have four hours to exit the cave and call in
0:27:14 > 0:27:16before the rescue team are dispatched.
0:27:42 > 0:27:43Yeah, I'm not giving up.
0:27:46 > 0:27:48I'm going to fight it till the end.
0:27:52 > 0:27:56Well, this is it, the deepest point in this cave system.
0:27:56 > 0:28:00I've never spent this long underground and I never realised
0:28:00 > 0:28:03that there's such a magical world down there.
0:28:03 > 0:28:06It's been an awesome day and an awesome adventure.
0:28:06 > 0:28:11'Nearly 15 hours underground, and a vertical descent of over 900ft...
0:28:13 > 0:28:16'..past amazingly beautiful cave formations...
0:28:18 > 0:28:20'..evidence of ancient creatures...
0:28:22 > 0:28:25'..and through some seriously technical challenges.'
0:28:27 > 0:28:29It was a lovely day when we went in there.
0:29:07 > 0:29:11Hello, I'm Sima Kotecha with your 90 second update.
0:29:11 > 0:29:15A man's been arrested after the bomb attacks in New York.