- 7/3/2025
Category
🛠️
LifestyleTranscript
00:00Sandan, the largest cave on our planet.
00:03This cave is so massive that it has a completely self-sustaining ecosystem with its own climate conditions.
00:10Hundreds of meters underground, the clouds you're used to seeing in the sky form inside this cave.
00:16Sandan even has an untouched prehistoric rainforest hidden far below the surface and a vast underground river.
00:23From transparent fish to colorful monkeys, over 250 endenic plant and animal species live in this underground world.
00:30Seven new animal species were recently discovered here and are unique to this place.
00:35Stretching 9 kilometers in length, this cave holds 38.5 million cubic meters of space.
00:41And its passages are so enormous that a 40-story skyscraper could fit inside.
00:47And its giant stalagmites are rising like towers of ancient cities.
00:51Walking inside, it's impossible not to feel as small as a tiny bug.
00:56Can a rock move on its own?
00:58Sandan even contains phytokarst rocks, which move towards the sun like semi-living organisms.
01:04Rare cave pearls and many other unique formations are also found here.
01:08For 3 million years since its formation, the world had no idea about this cave's existence until it was fully explored in 2009 in Vietnam.
01:17Now, its time for you to see the largest cave on earth.
01:21Individual access is forbidden to protect both visitors and the fragile environment.
01:26This expedition is operated by Oxalis, the only authorized agency.
01:31To reach Song Dong, we've tracked through the jungle for 9 hours.
01:34And now, we must pass through N cave, the world's third largest cave.
01:38This cave serves as a gateway to the world's largest cave.
01:43It's crucial to be fully prepared for every possibility.
01:46So, before setting out on this journey, we did deep online research about Song Dong and its surrounding area
01:52to learn about everything that we would need to know.
01:54Now, we're heading towards the beach inside the cave.
01:57Over the centuries, water from nearby rivers gradually carved this place.
02:02The ceiling is 145 meters high, and the cave is 200 meters wide.
02:07During the flooding season, much of this empty space is submerged underwater.
02:12You can understand from the basket over there, the water levels rise so much that it can carry objects up to that level.
02:19With a breathtaking lake in front of us, it was impossible not to take a quick dip.
02:26At dusk, the sound of swift birds echoes in the cave.
02:30Because of their short and weak legs, these birds can't take off from the ground and must jump from a high place to fly.
02:37If they are trapped on the ground, it means death is certain for these birds.
02:42This one was unlucky and waited to die.
02:45At sunrise, we're ready for the journey to Song Dong.
02:47If we call this cave a neighborhood, then Song Dong is a massive city in comparison.
02:56We will move to the darkness now.
02:58I can't help but wonder what awaits us in Song Dong.
03:01As we walk, dozens of crickets on the ground start jumping from side to side.
03:06The ground is covered with centuries of bat guano.
03:10Above us, countless bats hang in deep sleep.
03:13But some are awake and constantly defecating on us.
03:17So it's not a good idea to look up.
03:24That's how my arm loops.
03:26We pass by formations that look like travertine.
03:29The limestone steps take us to the path that leads to Song Dong.
03:32Wow.
03:33The view here is amazing.
03:35You can see some water coming down from both sides.
03:38End Cave welcomed us for a night deep in the jungle.
03:41Now, it's time to meet Song Dong Cave.
03:43It's trying to come to me, you know.
03:45It's moving towards me.
03:47It knows what to leach on.
03:51It got too big.
03:54Beneath the soil we walk on lies the 450 million year old limestone formation,
04:00which began forming long before the existence of humans or even dinosaurs.
04:05This calcium rich limestone is composed of shells and skeletons of ancient sea animals
04:10that sank to the ocean floor and gradually compressed over millions of years.
04:14However, since calcium dissolves easily in acid,
04:17acid rain slowly erodes limestone and forms caves over time.
04:22This is how the world's largest cave was formed by rain dissolving limestone.
04:27A challenging final climb brings us down to the grand entrance of Song Dong.
04:32As we move deeper, everyone's switching on their headlamps now.
04:35This path will lead us to the hope and vision passage.
04:38In this nine kilometer long cave, there is so much to explore.
04:42We might be the first to record newly discovered animals.
04:45This is the entrance of Song Dong Cave.
04:48You can see those people look tiny at the entrance.
04:51Even just a few steps in, we're surrounded by incredible cave formations.
04:55The water rich in minerals flows down from the ceilings or walls
04:59and builds these beautiful rimstone pools over time.
05:03The very first animal greeting us is a cricket.
05:06We are making our way through the rocks.
05:09Some stalagmites are sparkling in pure white because of the mineral type they're composed of.
05:14It looks like a diamond.
05:15Yes, it does.
05:16There's a huge stalactite in bronze color resembling frozen waterfalls.
05:21The orange-brown hue suggests the presence of iron or other minerals mixed within the limestone.
05:27Some stalactites have actually broken off from the ceiling and fell down to the ground.
05:32That one in the middle is a fault line.
05:34It was formed because of tectonic movements of the earth.
05:37Song Dong's enormous size is not just the result of water erosion,
05:41but also the fractures caused by tectonic movements,
05:44which created pathways for water to flow deeper.
05:47There's a huge river in this part of the cave.
05:50If you fall, you can't swim.
05:53It's so fast.
05:54Heavy rains feed many rivers here,
05:56and a large and fast river now flows through the cave.
05:59How did this come to life?
06:03We are like hundreds of meters inside the cave.
06:06There is no sunlight.
06:07Heavy floods can bring soil and plant stems into the cave.
06:10That's why we see a sprouted seed here.
06:12Unfortunately, without sunlight, they won't survive for long.
06:16The flood also brought spores in,
06:18so now there are mushrooms growing here.
06:20The moisture and darkness are perfect for them.
06:22Just yesterday, the water reached up to here.
06:24It carried a lot of mud with it.
06:26It's so recent, as if the flood just happened here.
06:29Signs of the incident are still visible.
06:32We reached the Hope and Vision Passage.
06:34This is the largest part of the cave.
06:36I'm standing next to the tallest stalactite mine in the world.
06:39It is 80 meters high.
06:41It took an average of 800,000 years
06:43for these minerals to accumulate on the ground
06:46as water dripped from the ceiling
06:48and formed this massive stalagmite.
06:50The reason it got so huge
06:52is because it grew in a part of the cave
06:54where the ceiling is over 170 meters high
06:56and more than 130 meters wide.
06:58So this part of the cave is as large
07:00as a 40-story skyscraper could fit,
07:03and even a double-decker aircraft could fly through.
07:06You can see the light coming from the first dolin very far ahead.
07:09That's where we are heading.
07:11We spot cloudy-like white catches on the ground.
07:14What is this?
07:15A spiderweb.
07:16When they sense vibrations of a trapped insect,
07:18the spider jumps out, bites the prey,
07:21and returns to the funnel to eat.
07:23These are sand towers.
07:24When water drips from above,
07:26the parts under the pebbles are protected
07:28while their surroundings erode.
07:30And in the end, it forms these towers.
07:33It looks like a small metropolis.
07:36If you carefully look at it,
07:37there's a guy standing on the top of that rock.
07:40Our teammate in the far distance
07:41is now standing on a stalagmite of 60 meters in length.
07:45We move three kilometers forward in the cave.
07:48This is our camping site.
07:49Imagine sleeping here, looking at this view.
07:52From here, you can partially see the first dew line.
07:54It might look like the cave's exit,
07:56but it's actually the first of two massive dew lines.
07:59And from here on, things will get more incredible.
08:02The temperature difference between the outside
08:04and the inside of the cave
08:05forms mist and clouds inside the cave.
08:08The area beyond them is called Watch Out for Dinosaurs.
08:11We will explore that place tomorrow.
08:13For now, it's time to rest.
08:15Now we are going to First Dolin.
08:17This is the next day.
08:18There will be a lot of things that we will see today.
08:21Let's go.
08:23We are crawling through narrow passages
08:25to get to the first dew line.
08:27A very narrow point.
08:29These sticky threads are traps belonging to cave worms.
08:33They produce a blue-green light from their tail
08:35to attract flying insects to these sticky threads.
08:38Once an insect gets stuck,
08:40the larva pulls up the thread with its mouth
08:42and eats its prey.
08:43This limestone is the oldest limestone in Southeast Asia.
08:46It is more than 400 million years old.
08:48While some sea creatures become part of the limestone,
08:51others mineralized and ended up as fossils,
08:55like you see in this example.
08:56We will get into the details of this fossil later.
08:59We are almost there.
09:00Sun!
09:01Well, it takes for water droplets to reach the ground
09:06for like 20 seconds from up there.
09:09What is the height of this wall?
09:11It is around 140 meters.
09:13Everything is huge here.
09:15When you look up,
09:17you can see the trees of the rainforest surrounding the opening.
09:20But right now,
09:21we are meters below and still inside the cave.
09:24The reason why this hole exists
09:26is that hundreds of thousands of years ago,
09:28the river flowing inside Songdong
09:30eroded the limestone and weakened the roof.
09:33The roof couldn't hold up and collapsed,
09:35creating this giant hole above.
09:37So the light gave life to these algaes and mosses.
09:40In the afternoon, we'll go to doline number two.
09:43It's very different.
09:44You'll see a real jungle there.
09:45But first,
09:46let's see the first of the last two incredible formations here.
09:49This is also a stalagmite.
09:52But it's a different one.
09:54It owes its unique layered shape to the waterfalls.
09:58These are phytokarst formations.
10:01They are rare limestone formations
10:03shaped by the growth of algae, mosses,
10:05and microorganisms together with calcium carbonate.
10:08Since both biological and geological processes shape them,
10:12they're like partly a living and partly non-living.
10:15Here, you can see the phytokarst formations
10:17moving toward the sun like a hand extending from the cave.
10:21Climbing one kilometer down and up in the dark,
10:24we finally reached our next destination.
10:26This is the second dolan,
10:27much bigger than the first one.
10:29This looks amazing.
10:31All of a sudden,
10:32we are in a forest in a cave.
10:34Look here.
10:35They're so dense.
10:36The roof of the cave at this point collapsed as a result
10:39of the intersection of two main faults,
10:41forming a dew line on the surface 252 meters above where we are.
10:45The collapsed cave roof allowed sunlight to enter,
10:48giving rise to an entirely new ecosystem.
10:51Despite extreme conditions,
10:52plants and animals have managed to adapt
10:55and turn this place into a unique underground rainforest.
10:58As we move forward towards the light,
11:01the height of the plants grow.
11:03The soil makes it perfect to form a rainforest.
11:06A large portion of the soil here consists of bat guano.
11:09It is accumulated for millions of years and is highly fertile.
11:13The soil here is deep and full of small holes.
11:16There is an insect in each hole,
11:18and the insects are making traps in these holes to catch animals.
11:21This jungle is huge.
11:23The biologists have found more than 200 species of plants
11:27and almost 60 species of animals living in this area.
11:30There are some monkeys on trees.
11:32This might be the only cave where monkeys live.
11:35Most primates typically prefer trees as their habitat,
11:38and cave environments are not suitable for them.
11:41However, this extraordinary cave has become a new living space for certain species.
11:46We came across a centipede,
11:49and snakes are living in this forest as well.
11:52The sound of this forest is calming.
11:59Even the explorers, who first came here in 2009,
12:02thought they'd found the exit for a moment.
12:04Remember that we are in a cave.
12:06This cave has its own rainforest.
12:08All of these trees get thinner but taller
12:11to reach the sunlight coming from above.
12:13That's why all of them are very thin.
12:16but very tall compared to their width.
12:18Certain trees reach heights of 40 to 50 meters.
12:21It's because the trees prioritize height to maximize sunlight absorption.
12:26This is the remains of a snail.
12:28Monkeys catch these snails and break them with stones,
12:31then eat them.
12:32As we move through the cave,
12:33we start coming across signs red-shinned dukes have left behind.
12:37Look, so many snails.
12:39Most of them are broken and probably eaten by a monkey.
12:42We kind of forget we're in the cave because it's so massive.
12:46This is where we are going to camp tonight.
12:48It's our fourth and final day in the cave.
12:50Today, we navigate through a water-filled passage
12:53before reaching the Great Wall of Vietnam.
12:56The stalagmites here look fascinating,
12:58almost like the work of a sculptor.
13:00A pool of water surrounds this column and fish are swimming in it.
13:04These fish have no eyes as they have adapted to live in this total darkness.
13:08Instead, their other senses got stronger over time.
13:11See how it doesn't give any reaction to the shadow of my hand or the movement?
13:16It doesn't see anything.
13:19Like the fish, this cricket is completely blind.
13:24It doesn't see me.
13:27These super rare formations are called cave pearls.
13:30They are usually one centimeter in diameter,
13:32but here, since they are too old,
13:34some of them are as big as a tennis ball.
13:36Just like real pearls, they form around a tiny nucleus,
13:39such as a grain of sand,
13:41with layers of minerals slowly building up over time.
13:44They need a few hundred years to be fully formed.
13:47As we push further into the cave,
13:49something unexpected catches our eyes.
13:51These are deer bones.
13:53They're estimated to be 500 years old.
13:56There is one last challenge ahead.
13:58An 80 meter high karst wall,
14:00called the Great Wall of Vietnam.
14:02To reach there,
14:03we must also pass through a 600 meter long Passchendaele Passage.
14:07The passage is now filled with water
14:09and is turned into a breathtaking jade green lake.
14:12It's so high that the light does not reach the very top.
14:19After the wall,
14:20the light from the exit is visible from 500 meters away.
14:23We've explored the world's largest cave,
14:25from one end to the other.
14:26Yet on the fourth day of the exploration,
14:28one mystery still remains.
14:30Which ancient creature,
14:31the fossil we saw in Sondom belongs to?
14:34I'm opening Opera browser and quickly navigating to the cave's website to check the related article.
14:39Here we'll find the same fossil's image and its description.
14:43I'm gonna press command slash or control slash to open Aria.
14:47It's a built-in AI tool.
14:49Let's ask it to highlight the key points in this article.
14:53The article mentions two different coral fossils,
14:56but doesn't specify which image belongs to which creature.
14:59Luckily, Aria has image recognition feature.
15:02I'm gonna upload the image and ask again.
15:05Okay.
15:08It identifies the fossil we saw as Tetracoralia.
15:11Let's check for more information on this sea creature.
15:14First, I'm using the tab islands feature to effortlessly group tabs by topic and save space.
15:20I can expand or collapse them as needed.
15:22I'm splitting the browser window to view both websites side by side.
15:26It appears that Tetracoralia or rugosa went extinct 300 million years ago.
15:31This carnivorous species is believed to have had tentacles to catch its prey and grew up to 10 centimeters.
15:37Because it is extinct today, we don't know exactly what this animal looked like.
15:41But with Aria's image generation feature, we can create a possible visual for this animal.
15:47Here's an illustration of a living Tetracoralia drawn as a colony with tentacles.
15:53By the way, Tab Traces feature, as you can see here,
15:56help us see our recent visited tabs by darkening the underscore.
16:00The darker the underline, the more recently the tab was visited.
16:04Using Opera's smart tools, I believe that we identified which creature this fossil belongs to.
16:09Opera also enhances workflow with a floating music player and customizable themes with many other features.
16:16Download Opera now from the link in the description box or pinned comment to take your browsing experience to the next level.
16:23Thank you for watching. See you in the next one.
16:25Ruhi Chenet was here.
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