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0:00:35 > 0:00:38- Wales has a subterranean landscape.
0:00:41 > 0:00:43- Caves created by water.
0:00:47 > 0:00:49- Powerful, wild rivers.
0:00:52 > 0:00:53- Quarries created by man.
0:00:58 > 0:00:59- Huge chambers...
0:01:00 > 0:01:03- ..and long, endless tunnels.
0:01:05 > 0:01:07- They're dangerous places...
0:01:10 > 0:01:15- ..but more beautiful at times - than anywhere on the surface.
0:01:17 > 0:01:20- Very few people - have seen these sights.
0:01:21 > 0:01:24- Little filming has taken place here.
0:01:27 > 0:01:31- This is my exploration - of Wales's subterranean landscape.
0:01:32 > 0:01:37- Beneath the Surface
0:01:54 > 0:01:58- These are the Brecon Beacons, - in the upper Swansea Valley.
0:01:58 > 0:02:02- The rock here is very special. - It's limestone.
0:02:02 > 0:02:07- It deteriorates when it comes - into contact with water.
0:02:08 > 0:02:11- The effect of this - is more visible underground.
0:02:11 > 0:02:16- This area is among the best places - in Britain to see caves.
0:02:16 > 0:02:21- My journey beneath the surface - of Wales starts here.
0:02:27 > 0:02:32- Ogof Ffynnon Ddu cave, near Penwyllt - in the upper Swansea Valley.
0:02:34 > 0:02:38- The entrances to many caves - are accessible and wide...
0:02:38 > 0:02:42- ..but that isn't the case - with Ogof Ffynnon Ddu!
0:02:44 > 0:02:48- Having navigated your way - through a small entrance...
0:02:48 > 0:02:52- ..you must crawl and climb - through narrow tunnels.
0:02:53 > 0:02:57- Having descended a quarter of a mile - beneath the earth's surface...
0:02:59 > 0:03:01- ..the cave opens out - into a huge chamber.
0:03:10 > 0:03:14- Cave exploration - shouldn't be undertaken alone.
0:03:14 > 0:03:16- Caves are dangerous places.
0:03:19 > 0:03:24- You must travel as part of a team, - both for safety reasons...
0:03:24 > 0:03:28- ..and to help illuminate - the subterranean sights.
0:03:32 > 0:03:35- The chamber walls - are formed from huge blocks.
0:03:39 > 0:03:42- They may appear man-made...
0:03:45 > 0:03:47- ..but nature is the builder.
0:03:49 > 0:03:52- These limestone blocks - were created by water.
0:03:58 > 0:04:01- I'm resting here - and enjoying the tranquillity.
0:04:02 > 0:04:06- The only sound I can hear - is water dripping down the rocks.
0:04:06 > 0:04:09- Having worked my way - through tunnel after tunnel...
0:04:09 > 0:04:13- ..and countless confined spaces...
0:04:13 > 0:04:15- ..the cave has opened out at last.
0:04:16 > 0:04:19- This is the aptly-named Big Chamber.
0:04:19 > 0:04:23- There's enough room for a chapel - and a large congregation.
0:04:23 > 0:04:26- I've walked across the land - above this cave...
0:04:27 > 0:04:32- ..oblivious to the fact there was - such a huge chasm beneath my feet.
0:04:42 > 0:04:46- Most caves are formed - when water dissolves soft rock.
0:04:52 > 0:04:55- Almost all Welsh caves - are formed in limestone.
0:04:56 > 0:05:00- The constant flow of water - in Ogof Ffynnon Ddu...
0:05:01 > 0:05:03- ..slowly dissolves the limestone.
0:05:06 > 0:05:11- Over a long period of time, - chambers and passages are formed.
0:05:18 > 0:05:21- Water also creates new formations.
0:05:32 > 0:05:38- This dissolved lime runs and hardens, - creating natural sculptures.
0:05:51 > 0:05:53- As water falls from the roof...
0:05:54 > 0:05:58- ..the dissolved lime - is gradually released.
0:05:58 > 0:06:01- It slowly reforms - to create stalactites.
0:06:29 > 0:06:31- Stalagmites form on the ground.
0:06:37 > 0:06:40- After hundreds - or thousands of years...
0:06:41 > 0:06:45- ..stalactites and stalagmites - connect to form columns.
0:06:48 > 0:06:51- The columns in Ogof Ffynnon Ddu...
0:06:51 > 0:06:55- ..are among the longest - found in any British cave.
0:06:56 > 0:06:58- Some are five metres high.
0:07:02 > 0:07:07- Lime can flow in curtains - from the roof down the walls.
0:07:14 > 0:07:18- The cave is decorated - with calcite formations.
0:07:25 > 0:07:31- Some of the formations found - in Welsh caves are truly remarkable.
0:07:32 > 0:07:36- They're far more intricate - than anything man could create.
0:07:36 > 0:07:38- Look at these columns.
0:07:38 > 0:07:41- They look like old candles...
0:07:41 > 0:07:45- ..where melted wax - has dripped haphazardly.
0:07:45 > 0:07:49- Look at those colours! - Pink, orange, cream and brown.
0:07:49 > 0:07:52- How were these sculptures formed?
0:07:52 > 0:07:56- As water flowed very slowly - across the limestone...
0:07:56 > 0:08:00- ..the acid in it - dissolved the rock.
0:08:00 > 0:08:02- As that dripped, it hardened.
0:08:03 > 0:08:07- These columns formed - over thousands of years.
0:08:09 > 0:08:10- These aren't very big...
0:08:11 > 0:08:15- ..but there are much larger ones - further into the cave.
0:08:15 > 0:08:19- Those were formed - over a far shorter period of time.
0:08:24 > 0:08:27- These are the small - Ogof Ffynnon Ddu columns.
0:08:28 > 0:08:31- The large columns - lie deep within the cave.
0:08:35 > 0:08:38- They're one of the wonders of Wales.
0:08:42 > 0:08:46- Special permission is needed - to see and to film this sight.
0:08:49 > 0:08:52- These columns are unique.
0:08:52 > 0:08:57- They were formed as a result - of human activity on the surface.
0:08:59 > 0:09:04- Above the cave, there was a kiln - in which limestone was burnt.
0:09:08 > 0:09:12- Over a period of time, - lime waste dissolved in the rain...
0:09:12 > 0:09:17- ..and flowed through the rocks, - forming these columns in the cave.
0:09:18 > 0:09:23- Sculptures formed half by nature, - and, accidentally, half by man.
0:09:33 > 0:09:39- The lime kiln above Ogof Ffynnon Ddu - has disappeared without a trace...
0:09:41 > 0:09:45- ..but it's obvious why the lime - industry thrived in Penwyllt.
0:09:46 > 0:09:50- Hills in this part of the Beacons - are almost pure limestone.
0:09:51 > 0:09:57- Thanks to the limestone pavements, - this is a National Nature Reserve.
0:09:59 > 0:10:03- It's an important site, - both above and below ground.
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0:10:13 > 0:10:18- There are several sections of Ogof - Ffynnon Ddu in the Brecon Beacons.
0:10:18 > 0:10:22- Lower down the Penwyllt hills, - the cave is still forming.
0:10:22 > 0:10:24- This part is wet and dangerous.
0:10:34 > 0:10:35- Rivers flow here.
0:10:45 > 0:10:50- Ffynnon Ddu means black spring - and this is how it got its name.
0:10:51 > 0:10:54- The spring bubbles its way - through a black cave.
0:11:02 > 0:11:05- This is the deepest cave in Britain.
0:11:08 > 0:11:10- It drops over 300 metres.
0:11:17 > 0:11:18- Wow!
0:11:19 > 0:11:22- This tunnel - through which the river flows...
0:11:22 > 0:11:25- ..stretches for four miles - up the mountain.
0:11:25 > 0:11:30- I've followed it for a mile - and it's very tiring.
0:11:30 > 0:11:35- Sometimes the water gushes, - sometimes it's slow and deep.
0:11:36 > 0:11:40- The weather has been stormy - and there has been heavy rainfall...
0:11:41 > 0:11:44- ..so water levels can rise quickly - and fill the cave.
0:11:45 > 0:11:48- That's what makes this - a dangerous place.
0:11:48 > 0:11:50- You must be really careful.
0:11:50 > 0:11:53- I'll follow this tunnel - for another mile.
0:11:53 > 0:11:57- This is the longest tunnel - of its kind in the country.
0:12:06 > 0:12:10- A network of tunnels - cross above and below each other.
0:12:13 > 0:12:16- They create - a complex and confusing labyrinth.
0:12:21 > 0:12:26- When the river finds an easier way - to flow through the rock...
0:12:27 > 0:12:30- ..it creates deep holes - and dangerous whirlpools.
0:12:36 > 0:12:39- This is one of a series of four - big whirlpools.
0:12:40 > 0:12:43- There's one here, - another one there...
0:12:45 > 0:12:47- ..and two further down the tunnel.
0:12:47 > 0:12:50- They're up to 20 feet, - or 6 metres, deep.
0:12:53 > 0:12:57- There are still stones - down in those depths...
0:12:57 > 0:13:00- ..so they keep turning - and boring into the rock.
0:13:00 > 0:13:03- These pools get deeper every year.
0:13:03 > 0:13:06- This is very dangerous - for any caver.
0:13:06 > 0:13:11- If you fell in there, it would be - like being in a washing machine.
0:13:11 > 0:13:15- You'd spin around and around - and could easily drown.
0:13:15 > 0:13:20- Cavers laid down a metal pole - to help them cross the whirlpool.
0:13:27 > 0:13:32- By gushing through the rock, - the river creates round tunnels.
0:13:36 > 0:13:38- The walls are totally clean.
0:13:40 > 0:13:43- The incessant flow of water - cleans them.
0:14:00 > 0:14:03- I've said this before - but I'll say it again.
0:14:03 > 0:14:07- I'm amazed by some of the patterns - which are on this rock.
0:14:07 > 0:14:11- They're much more intricate - than anything a human could create.
0:14:12 > 0:14:16- This pattern is like the one - waves leave on a sandy beach.
0:14:17 > 0:14:19- There are hollows here and there.
0:14:20 > 0:14:24- These patterns tell us - this cave was created by a river.
0:14:24 > 0:14:29- That comes as no surprise, - because the river's right here.
0:14:29 > 0:14:33- They also reveal in which direction - the water flowed.
0:14:33 > 0:14:35- The river flowed down this way.
0:14:35 > 0:14:39- We know this because - the lower section is smoother.
0:14:39 > 0:14:42- If the hollows - are tightly bunched...
0:14:42 > 0:14:46- ..it proves that the water - flowed very quickly.
0:14:48 > 0:14:51- It's wonderful - to be able to read the rock.
0:14:55 > 0:15:00- The river created hollows which - look like metal on the black rock.
0:15:04 > 0:15:08- In another part of the cave, - the rock changes again.
0:15:10 > 0:15:15- The flow isn't as strong here - and water rarely fills the tunnels.
0:15:16 > 0:15:19- The lime which dissolved - in the water...
0:15:19 > 0:15:22- ..had an opportunity - to reform on the walls.
0:15:23 > 0:15:28- The colours and shapes - in a cave such as this...
0:15:28 > 0:15:30- ..are amazing and a real eye-opener.
0:15:30 > 0:15:34- Where the water gushes down...
0:15:34 > 0:15:37- ..it sweeps everything - downstream with it.
0:15:37 > 0:15:41- Here and there, - the water flows very gently...
0:15:41 > 0:15:46- ..and the calcium carbonate - carried by it settles on the rock.
0:15:49 > 0:15:51- It covers the rocks - in an orange blanket.
0:15:53 > 0:15:55- It reminds me of melted ice cream.
0:15:56 > 0:16:00- Its patterns and colours - are fascinating.
0:16:03 > 0:16:07- Ogof Ffynnon Ddu - is one of Europe's largest caves.
0:16:12 > 0:16:17- It's famous all over the world for - its wonderful subterranean views...
0:16:18 > 0:16:22- ..but it isn't the only cave - in the Brecon Beacons.
0:16:24 > 0:16:27- There's an equally important cave - in the Swansea Valley.
0:16:27 > 0:16:32- More famous than Ogof Ffynnon Ddu, - this is Dan-yr-Ogof.
0:16:36 > 0:16:39- Thousands of people - visit the cave every year.
0:16:44 > 0:16:48- Showcaves give people a taste - of the subterranean life of Wales.
0:16:52 > 0:16:57- Few visitors realize the caves are - far larger than the areas they see.
0:17:00 > 0:17:05- Most of the cave system - hasn't been fully explored as yet.
0:17:08 > 0:17:12- Dan-yr-Ogof stretches much further - underground than you'd expect.
0:17:13 > 0:17:16- The problem is - you must cross a deep lake...
0:17:16 > 0:17:20- ..and a very narrow section - further along.
0:17:20 > 0:17:25- The showcaves which are open - to the public are magnificent...
0:17:25 > 0:17:29- ..but there are even better sections - deeper in the cave system.
0:17:30 > 0:17:35- It was first explored in 1912 by - the Morgan brothers from Abercraf.
0:17:35 > 0:17:38- Imagine having - to push your way inside...
0:17:38 > 0:17:41- ..without the aid - of modern equipment.
0:17:42 > 0:17:45- It's hard work even now, - believe you me.
0:17:51 > 0:17:56- Dan-yr-Ogof stretches over ten miles - beneath the Black Mountain.
0:18:01 > 0:18:05- The Morgan brothers faced the lake - in the first section of the cave.
0:18:08 > 0:18:11- They used a coracle - to cross the lake.
0:18:15 > 0:18:17- I'm using a canoe.
0:18:19 > 0:18:21- Just as they did a century ago...
0:18:22 > 0:18:26- ..I had to cross three lakes - and climb waterfalls.
0:18:41 > 0:18:44- The subterranean river - flowed quickly.
0:18:44 > 0:18:48- The Morgan brothers - needed great mental strength...
0:18:49 > 0:18:53- ..to embark on this journey - for the first time.
0:18:57 > 0:19:01- What if the water levels - rose without warning?
0:19:05 > 0:19:08- For about a quarter of a mile...
0:19:08 > 0:19:12- ..I've walked across areas - where water gushes over the rocks.
0:19:13 > 0:19:15- The noise is deafening!
0:19:16 > 0:19:20- Thankfully, it will be quieter - from this point onwards.
0:19:28 > 0:19:30- Unlike the Morgan brothers...
0:19:30 > 0:19:35- ..I can cross the deep pools - in the knowledge I'm quite safe.
0:19:35 > 0:19:40- I also know there's an amazing sight - to behold at the journey's end.
0:19:42 > 0:19:45- The Morgan brothers' journey - ended here.
0:19:50 > 0:19:54- This squeeze was too much, - even for the intrepid brothers.
0:20:20 > 0:20:21- This is hard work.
0:20:22 > 0:20:27- Imagine being the first man - to come down here.
0:20:28 > 0:20:30- It's daunting enough for me...
0:20:30 > 0:20:34- ..knowing dozens of people - have been here before me.
0:20:34 > 0:20:39- They tell me what's at the other end - is a sight which is worth seeing.
0:20:40 > 0:20:42- I hope that's true!
0:20:42 > 0:20:43- On we go.
0:20:43 > 0:20:45- This is such hard work!
0:20:47 > 0:20:50- The worst thing is knowing - I must come back the same way.
0:20:57 > 0:21:02- The first person to squeeze through - the Long Crawl did it 50 years ago.
0:21:03 > 0:21:07- She was a woman from Swansea - called Eileen Davies.
0:21:16 > 0:21:19- Her efforts were well rewarded.
0:21:26 > 0:21:28- A breathtaking sight awaited her.
0:21:48 > 0:21:50- I paddled across - a subterranean lake.
0:21:51 > 0:21:55- I waded through another lake, - up to my armpits in icy water.
0:21:55 > 0:21:59- I crawled through a tunnel - no wider than a rabbit hole.
0:21:59 > 0:22:03- I'm soaked to the skin - and my muscles are aching.
0:22:03 > 0:22:06- I'd do it all again - to reach this place.
0:22:06 > 0:22:09- This is called Cloud Chamber.
0:22:09 > 0:22:11- I've never seen such a thing - in my life!
0:22:12 > 0:22:15- To be honest, I didn't even know - such a thing existed.
0:22:16 > 0:22:18- It's a geological miracle.
0:22:22 > 0:22:26- It has been called - Britain's greatest natural wonder.
0:22:29 > 0:22:32- The adjective 'wonderful' - is often overused...
0:22:35 > 0:22:36- ..but not in this context.
0:22:40 > 0:22:44- Here, beneath the Beacons, - is a natural sculpture.
0:22:45 > 0:22:49- It was created as a result of the - formation of limestone in Wales...
0:22:50 > 0:22:52- ..over 300 million years ago...
0:22:52 > 0:22:57- ..limestone that was subsequently - transformed by water.
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0:23:09 > 0:23:12- There are quarries - in most parts of Wales.
0:23:12 > 0:23:18- It's a rich country geologically, - with a great deal of useful stone.
0:23:19 > 0:23:22- One of Wales's oldest quarries - is on Anglesey.
0:23:22 > 0:23:28- Parys Mountain near Amlwch - has been excavated for 3,000 years.
0:23:30 > 0:23:35- This landscape has been created - by generations of miners...
0:23:35 > 0:23:38- .searching for metals, - mainly copper.
0:23:40 > 0:23:44- The landscape is unnaturally - coloured by metal mine waste.
0:23:47 > 0:23:52- Initially, ore was worked - on the surface from shallow shafts...
0:23:52 > 0:23:56- ..but more recent miners - dug shafts underground.
0:24:14 > 0:24:19- This place is very unlike - any other I've visited.
0:24:19 > 0:24:21- There's enough space in general...
0:24:22 > 0:24:25- ..but here and there, - it gets incredibly confined.
0:24:25 > 0:24:31- Timber is used to prop up the roof - where there's a risk of collapse.
0:24:34 > 0:24:37- People worked down here - two centuries ago.
0:24:38 > 0:24:43- Exploring a mine is far more - dangerous than exploring a cave.
0:24:46 > 0:24:49- These tunnels - were created by man.
0:24:55 > 0:25:00- The walls and posts - supporting the roof are very fragile.
0:25:01 > 0:25:06- It's also a dirtier location, - with mud and wet clay everywhere.
0:25:07 > 0:25:11- The mud is full of acid - formed from the metal ores.
0:25:20 > 0:25:24- Despite the poisonous conditions, - there is life here.
0:25:33 > 0:25:36- The colours seen underground...
0:25:36 > 0:25:39- ..are the same ones - seen on the surface.
0:25:39 > 0:25:45- These oranges, browns and yellows - aren't created by copper...
0:25:45 > 0:25:46- ..but by iron.
0:25:46 > 0:25:49- There's clay underfoot here.
0:25:49 > 0:25:52- It's so acidic - that it almost softens the rock...
0:25:52 > 0:25:54- ..turning it back into clay.
0:25:55 > 0:26:00- This may look like a stalactite, - but it isn't.
0:26:00 > 0:26:02- This is called a snotite.
0:26:02 > 0:26:05- It looks like snot and isn't solid.
0:26:08 > 0:26:09- As you can see, it's soft.
0:26:10 > 0:26:12- It's created by bacteria.
0:26:13 > 0:26:19- They're one of very few living things - that can survive without sunlight.
0:26:20 > 0:26:24- It gets its nutrients - from the metals in the rock.
0:26:24 > 0:26:26- It then creates these snotites.
0:26:26 > 0:26:29- This snotite must be decades old.
0:26:32 > 0:26:38- From time to time, you see something - that needs a new Welsh name.
0:26:42 > 0:26:46- Perhaps 'snotidau' would describe - these formations perfectly.
0:26:52 > 0:26:58- Parys mine is famous for its copper, - but very little of it remains.
0:27:04 > 0:27:07- When you do find some, - it can be seen very clearly.
0:27:09 > 0:27:11- It's a bright vivid green.
0:27:13 > 0:27:17- This was one of the reasons - the Romans came to Wales.
0:27:17 > 0:27:19- They sought this very rock.
0:27:23 > 0:27:27- Since Roman times - and even earlier than that...
0:27:27 > 0:27:31- ..people have come to Wales - in search of precious rocks.
0:27:31 > 0:27:34- In the north, - the most important rock was slate.
0:27:39 > 0:27:44- On the slopes above Aberglaslyn - lies the disused Croesor Quarry.
0:27:45 > 0:27:50- Unlike any other slate quarry, - it was entirely underground.
0:27:54 > 0:27:58- It has a subterranean link - to Rhosydd Quarry...
0:27:58 > 0:28:00- ..on the other side of the hill.
0:28:02 > 0:28:06- It's possible to walk - from one side to the other...
0:28:06 > 0:28:11- ..but it's a hazardous journey - which takes around seven hours.
0:28:16 > 0:28:18- Once inside the entrance...
0:28:18 > 0:28:23- ..you're faced with a huge chamber - and steps with no safety features.
0:28:30 > 0:28:34- The roof looks fragile, with rocks - that could fall at any time.
0:28:41 > 0:28:44- The quarry has been closed - for over 80 years.
0:28:44 > 0:28:49- Once work ceases, a quarry - instantly becomes a dangerous place.
0:28:56 > 0:28:59- Without pumps, - the chambers fill with water.
0:29:04 > 0:29:06- The water is clear and cold.
0:29:09 > 0:29:14- This chamber plunges 20 metres - below the beam seen near the surface.
0:29:19 > 0:29:23- It was there to support something - at the bottom of the chamber.
0:29:26 > 0:29:31- This is as far as anyone can venture - relatively safely and with caution.
0:29:32 > 0:29:35- From this point, - I need climbing equipment...
0:29:35 > 0:29:39- ..and the support - of experienced cavers.
0:29:39 > 0:29:45- The size of some of the chambers - only becomes clear when you're here.
0:29:46 > 0:29:49- The men who created them - worked extremely hard.
0:29:49 > 0:29:52- I'm about to embark - on an 80 foot descent.
0:29:53 > 0:29:55- It really hammers it home...
0:29:55 > 0:30:00- ..that exploring somewhere like this - isn't something you do lightly.
0:30:06 > 0:30:10- Abseiling underground - is an odd feeling.
0:30:14 > 0:30:17- I've done this many times - on mountains...
0:30:17 > 0:30:21- ..but plunging into the darkness - is a strange experience.
0:30:23 > 0:30:26- The old quarrymen - used simple ropes to do this.
0:30:27 > 0:30:29- They were brave workers.
0:30:36 > 0:30:41- Having reached the bottom, - I can see how vast the chamber is.
0:30:41 > 0:30:46- It's one of the largest subterranean - chambers in any slate quarry.
0:30:46 > 0:30:50- It was created by hand, - without the aid of modern machines.
0:31:02 > 0:31:07- Leading from the chamber, - tunnels head in several directions.
0:31:14 > 0:31:16- This is an old railway track.
0:31:16 > 0:31:19- Two tracks met at this junction.
0:31:19 > 0:31:23- One came from that direction - and one came from behind me.
0:31:23 > 0:31:27- They carried slate from the quarry - out into the open air.
0:31:27 > 0:31:30- The trucks would have been pushed.
0:31:30 > 0:31:33- It's completely silent here now...
0:31:33 > 0:31:37- ..but imagine how busy it was - when hundreds of people worked here.
0:31:38 > 0:31:41- Imagine the noise of explosions - and men talking.
0:31:41 > 0:31:43- It's all gone.
0:31:52 > 0:31:57- There was no electric light. - Candles illuminated the tunnels.
0:31:57 > 0:32:00- Because this area - was far from the entrance...
0:32:00 > 0:32:03- ..much of the equipment - was left behind.
0:32:19 > 0:32:21- Chains were also left here.
0:32:21 > 0:32:24- These were put here - to help the men cross...
0:32:24 > 0:32:27- .from one side of the chamber - to the other.
0:32:34 > 0:32:38- I must do the same thing - but I'll use a far safer method.
0:32:39 > 0:32:44- There were paths from one side - of the mountain to the other...
0:32:44 > 0:32:48- ..but they're now either underwater - or they've collapsed.
0:32:48 > 0:32:53- You can't cross - unless you use a zip wire.
0:32:54 > 0:32:56- Swinging across like this - is the only safe way.
0:32:57 > 0:32:59- This is the method I must use today.
0:33:08 > 0:33:12- The quarrymen were used - to conditions underground.
0:33:15 > 0:33:20- It's an adventure for me, but they - had to do this to earn a living.
0:33:20 > 0:33:24- They had to work - in extremely dangerous conditions.
0:33:40 > 0:33:43- I have ropes to support me - as I cross the old bridge.
0:33:44 > 0:33:47- I doubt the old quarrymen - would have used any aids.
0:33:58 > 0:34:02- Having crossed the shaft, - a tunnel led to Rhosydd Quarry.
0:34:07 > 0:34:12- During the 1960s, chambers - and tunnels on the Croesor side...
0:34:12 > 0:34:16- ..were used to store explosives - by a local company.
0:34:17 > 0:34:20- They are no longer used - for that purpose.
0:34:22 > 0:34:25- The only remains now - are those of the quarry...
0:34:26 > 0:34:29- ..which operated here - between 1846 and 1930.
0:34:41 > 0:34:46- The most interesting things - are those items they left behind.
0:34:46 > 0:34:49- An old barrel, - the wood having rotted away.
0:34:49 > 0:34:52- This would have been - an old fuse box.
0:34:52 > 0:34:54- A black fuse snakes along here.
0:34:54 > 0:34:56- It would have burned slowly...
0:34:57 > 0:35:01- ..to give them time - to withdraw before the explosion.
0:35:01 > 0:35:03- Over there, - I can see a personal item.
0:35:05 > 0:35:07- It's an old cigarette packet.
0:35:07 > 0:35:10- One of the last quarrymen - must have left it there.
0:35:11 > 0:35:14- When we think about - the legacy of the quarries...
0:35:14 > 0:35:18- ..we think about - mountains of slate waste...
0:35:18 > 0:35:22- ..left in Blaenau Ffestiniog, - Llanberis and Bethesda.
0:35:22 > 0:35:24- It's important to remember...
0:35:25 > 0:35:30- ..that they also completely changed - the Welsh landscape underground.
0:35:34 > 0:35:39- The workers here deposited - most of the waste back underground.
0:35:39 > 0:35:43- That's why there are fewer mounds - outside the quarry.
0:35:49 > 0:35:51- This isn't waste.
0:35:51 > 0:35:54- It's a collapsed roof - on the Rhosydd Quarry side.
0:35:55 > 0:35:59- It's a timely reminder that - an old quarry is a dangerous place.
0:36:12 > 0:36:13- .
0:36:16 > 0:36:16- 888
0:36:16 > 0:36:18- 888- - 888
0:36:26 > 0:36:31- Dinas mine is near Pontneddfechan - in the Vale of Neath.
0:36:35 > 0:36:38- It has been closed - for almost 50 years.
0:36:47 > 0:36:51- The first thing which strikes you - is its sheer size.
0:36:59 > 0:37:04- You usually find narrow tunnels - when you explore an old mine...
0:37:04 > 0:37:06- ..but this feels very spacious.
0:37:11 > 0:37:15- There are no wooden beams - propping up the roof.
0:37:16 > 0:37:18- It's a location which feels safe.
0:37:20 > 0:37:23- The reason for that - is the way they mined here.
0:37:27 > 0:37:30- This is a pillar - which was left behind.
0:37:30 > 0:37:33- They used these large pillars - to prop up the roof.
0:37:34 > 0:37:38- It was a safe system which allowed - miners to work without worrying.
0:37:39 > 0:37:41- This was safer - and far easier for them...
0:37:42 > 0:37:46- ..than bringing in timber or iron - to support the roof.
0:37:47 > 0:37:52- They knew these pillars would last - much longer than timber or iron.
0:37:52 > 0:37:56- It was also easier because - they didn't have to dig this out.
0:38:01 > 0:38:04- They mined - silica-rich sandstone here.
0:38:07 > 0:38:11- The sandstone was used - to make special bricks...
0:38:11 > 0:38:14- ..that could withstand - high temperatures.
0:38:14 > 0:38:20- They were used to build furnaces - in factories in the Vale of Neath.
0:38:25 > 0:38:28- The bricks were also exported - across the world...
0:38:29 > 0:38:31- ..over a period of 150 years.
0:38:35 > 0:38:37- This is an interesting place.
0:38:38 > 0:38:39- Look at the roof.
0:38:39 > 0:38:44- The miners inserted iron pegs here - to support something.
0:38:46 > 0:38:48- There are more pegs over there.
0:38:48 > 0:38:50- There's iron in this rock.
0:38:55 > 0:38:57- Can you see those tiny stalactites?
0:38:57 > 0:39:01- They were created when water - flowed through the rock...
0:39:02 > 0:39:04- ..extracting iron as it flowed.
0:39:04 > 0:39:08- That iron sticks to the tip, - making the stalactite longer.
0:39:09 > 0:39:12- It looks like a nail - protruding from the roof.
0:39:17 > 0:39:21- All these tunnels - were dug with picks and shovels.
0:39:27 > 0:39:32- The workers mined the sandstone, - leaving pillars to support the roof.
0:39:41 > 0:39:43- This is the oldest part of the mine.
0:39:44 > 0:39:46- This dates back to 1790.
0:39:47 > 0:39:49- It's over two centuries old.
0:39:50 > 0:39:53- I can now see how they opened up - these huge chambers.
0:39:54 > 0:39:56- First, they dug the tunnels.
0:39:56 > 0:39:59- There's one here - and another one there.
0:39:59 > 0:40:03- There's another lower level - and another one below that.
0:40:03 > 0:40:07- You can see pick marks - on the walls and on the roof.
0:40:07 > 0:40:11- The miners came here day after day - without complaining.
0:40:11 > 0:40:15- They knew they had no choice - but to carry on with the work.
0:40:16 > 0:40:17- It's incredible.
0:40:30 > 0:40:35- Dozens of men worked here - when the mine was in its heyday.
0:40:37 > 0:40:40- The noise - would have been deafening...
0:40:41 > 0:40:44- ..and the air thick with dust.
0:40:54 > 0:40:58- On the surface, we tend to clear - old industrial remains...
0:40:58 > 0:41:03- ..but the industrial landscape - remains untouched underground.
0:41:06 > 0:41:11- Of course, mines are locked due to - the dangers lurking within them...
0:41:11 > 0:41:14- ..but they are then forgotten.
0:41:16 > 0:41:18- This water is really clear.
0:41:19 > 0:41:21- It's incredibly quiet here too.
0:41:21 > 0:41:24- All you can hear is dripping water.
0:41:24 > 0:41:27- Of the hundreds of metres - of tunnels here...
0:41:27 > 0:41:29- ..half of them are flooded.
0:41:32 > 0:41:34- This water is over 20 metres deep.
0:41:35 > 0:41:36- That's incredible.
0:41:36 > 0:41:41- When they worked here, - the water was constantly pumped out.
0:41:41 > 0:41:46- The mine closed in 1964 - and the pumps were switched off...
0:41:46 > 0:41:49- ..allowing the water - to rise to its natural level.
0:41:56 > 0:42:00- There may be no incredible natural - views in mines and quarries...
0:42:01 > 0:42:04- ..but they are landscapes - which record the past.
0:42:05 > 0:42:09- They're locations that are - a part of Welsh heritage.
0:42:18 > 0:42:21- The Pembrokeshire coast, - near St Govan's Head.
0:42:21 > 0:42:23- It's a dramatic sight.
0:42:23 > 0:42:27- The steep cliffs are continuously - pounded by the sea.
0:42:43 > 0:42:45- There are caves in the cliffs.
0:42:48 > 0:42:51- There are similar caves - along the coast of Wales.
0:42:53 > 0:42:56- It's very difficult - to explore these caves.
0:43:03 > 0:43:07- You've yet to see the crew which - accompanies me and keeps me safe.
0:43:11 > 0:43:15- It's important to stress - that exploring a sea cave...
0:43:15 > 0:43:17- ..can't be taken lightly.
0:43:18 > 0:43:21- You need an experienced team - around you.
0:43:58 > 0:44:00- Sometimes, merely reaching a cave...
0:44:01 > 0:44:05- ..is as much of an adventure - as exploring the cave itself.
0:44:05 > 0:44:10- It doesn't come more adventurous, - dangerous or dramatic than this.
0:44:10 > 0:44:14- This is Saint Govan's Cave - in south Pembrokeshire.
0:44:14 > 0:44:17- Simply reaching this cave - is a feat in itself.
0:44:21 > 0:44:26- I hang over the cliff, safe in the - knowledge I'm supported by ropes.
0:44:28 > 0:44:31- You wouldn't want to try this - without assistance.
0:44:41 > 0:44:44- The cave - offers some much-needed shelter.
0:45:07 > 0:45:12- It's hard to believe in a cave - half way down a steep cliff...
0:45:12 > 0:45:15- ..but there are - some ancient remains here.
0:45:17 > 0:45:20- Can you see the black line - beneath the mud?
0:45:21 > 0:45:25- It's charcoal, which tells us - this was an old fireplace.
0:45:25 > 0:45:29- It makes sense because - I'm close to the cave entrance.
0:45:29 > 0:45:32- Smoke from the fire - would have been drawn outside.
0:45:33 > 0:45:36- They could cook the animals - they had hunted on the fire.
0:45:37 > 0:45:43- Human and animal bones - have been found deeper into the cave.
0:45:44 > 0:45:47- This was a very important place...
0:45:47 > 0:45:50- .as were all caves - during those times.
0:45:50 > 0:45:53- We think of caves - as places to explore..
0:45:53 > 0:45:55- ..but they were once homes.
0:45:59 > 0:46:01- Stone Age people lived here.
0:46:04 > 0:46:08- The cave has changed very little - since then.
0:46:26 > 0:46:29- There are several chambers - and two entrances.
0:46:35 > 0:46:36- This is the best view.
0:46:41 > 0:46:44- This is known as The Window, - for obvious reasons.
0:46:44 > 0:46:47- This must be - one of the best views in Wales.
0:46:48 > 0:46:52- People lived in this cave - between 10,000 and 30,000 years ago.
0:46:52 > 0:46:56- It would have looked very different - back then.
0:46:56 > 0:46:58- This was the main entrance.
0:46:58 > 0:47:01- A shelf led to this entrance - in those days.
0:47:02 > 0:47:06- It was almost like a path - and allowed people to walk in here.
0:47:06 > 0:47:08- You can't do that today.
0:47:08 > 0:47:14- The sea would have been further out - and you could have seen dry land.
0:47:14 > 0:47:17- This is the view today.
0:47:21 > 0:47:23- The people who lived in the cave...
0:47:24 > 0:47:28- ..did so a couple of thousand years - following the Ice Age.
0:47:30 > 0:47:33- In those times, - sea levels were yet to rise.
0:47:35 > 0:47:38- The ice was still thick - in the Poles.
0:47:40 > 0:47:42- This would have been a wide valley.
0:47:44 > 0:47:47- You can imagine deer grazing here.
0:47:52 > 0:47:56- This was a good vantage point - from which to watch the deer...
0:47:56 > 0:47:59- ..and to formulate - a hunting strategy.
0:48:16 > 0:48:19- My journey underground - has been a real eye-opener.
0:48:20 > 0:48:25- It gave me the opportunity to see - landscapes I've never seen before.
0:48:27 > 0:48:32- These are locations where people - have lived, worked and explored...
0:48:33 > 0:48:35- ..since the early days - of the human race.
0:48:37 > 0:48:41- Very few people are fortunate enough - to have seen these sights.
0:48:43 > 0:48:47- It's important to remember they exist - and they're a part of Wales.
0:48:50 > 0:48:54- We must protect - our subterranean treasures.
0:49:24 > 0:49:27- S4C subtitles by Eirlys A Jones
0:49:27 > 0:49:27- .