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This is the entrance

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to one of the greatest
of natural wonders.

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Hang Son Doong, in Vietnam.

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It's thought to be the largest
cave on Earth.

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Here, 200 metres underground,

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for just a few weeks a year,

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sunbeams cast light through a hole
in the cave's roof.

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There is just enough light

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to enable plants to grow.

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But travel deeper,

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and darkness returns.

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And you reach the limit

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of where life can exist.

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These most extreme places
on our planet

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are often hard for us to reach.

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Indeed, this cave was only
recently discovered.

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And it contains many surprises.

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Cave pearls.

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Once tiny sand grains,

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now spheres the size
of tennis balls.

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And giant stalagmites...

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..formed over centuries

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by billions of individual
drops of water.

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Underground rivers have carved

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this great passage through
the limestone.

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Over five miles long

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and wide enough in places

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to accommodate a jumbo jet.

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And it is here,

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in the cave's furthest chamber,

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that life can be found.

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Translucent cave fish...

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..and shrimps.

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Isolated for millennia,

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feeding on little more than the
nutrients from the jungle above.

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The fish are completely blind

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and find their way about
by touch alone.

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These underground worlds are at
the very limit

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of where life can exist.

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But above ground,

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our planet's most extreme conditions

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are found at the poles.

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Here in the north,

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winter temperatures can drop to
-50 degrees Celsius.

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For four months of the year,

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there is barely a glimmer
of sunlight.

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But here, too,

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life finds a way to survive.

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A pack of Arctic wolves.

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Their dense fur has protected them

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through months of bitter cold.

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But now the sun is returning.

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This is Ellesmere Island.

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The short summer gives the wolves
a chance to rebuild their strength.

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But here in the Arctic...

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..life is never easy.

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This pack is led by an
experienced female.

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If she can't lead them to food,

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the coming winter could be
their last.

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Prey is spread over
such a vast area

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that they must be constantly
on the move...

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..in search of it.

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But finding prey is only
the beginning.

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Musk oxen.

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They are five times the size
of a wolf.

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The conflict between wolf and oxen
is an ancient one,

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and has been waged since
the Ice Age.

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OXEN GRUNT

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Each side knows the other's tactics.

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The wolves try to isolate

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the weak or the young.

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A calf stumbles...

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..and the pack leader immediately
closes in.

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But the herd regroups,

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horns at the ready.

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Stalemate.

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But it can only be brief.

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This time, the herd race
to higher ground.

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As they reach the top of the ridge,

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the males turn to defend themselves.

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Stalemate...

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..again.

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Every unsuccessful hunt

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leaves the pack weakened.

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This could be an easier meal.

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But something is not right.

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This musk ox has died
from a disease.

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Outbreaks like this are becoming
increasingly common

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as the climate warms across
the Arctic.

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Despite their hunger,

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the pack don't eat this carcass.

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Another herd.

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Another chance for the pack.

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This time, the wolves manage
to split the herd.

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That may improve their chances.

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The lead female makes sure
that the oxen

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do not reach the ridge again.

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With one less defender,
the calf is more vulnerable.

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A much-needed meal.

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The wolves must continue to
make the most

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of the remaining weeks of summer...

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..so when winter returns

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..they're ready to endure

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some of the harshest conditions

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that exist on planet Earth.

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Such inhospitable extremes

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are not only found at the poles.

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As altitude increases...

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..temperatures fall.

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Here, too, animals must make the
most of the seasonal change.

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Particularly if you're ready
to mate.

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A male common frog

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in the French Alps.

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He has spent all winter
hibernating under the ice.

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But now it's time to wake up.

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Being cold-blooded, he needs
the sun to warm his body.

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But once it sets
in a few hours' time,

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he could freeze to death.

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So finding a mate is urgent.

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The weather is good.

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And he starts to sledge.

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But this is not a one-frog race.

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Dozens are rushing to
the breeding pool.

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This many frogs out on the slopes...

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..doesn't go unnoticed.

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You can't afford any slips.

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It was all going so well.

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Made it.

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But all the females have already
got partners.

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There's only one thing for it.

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Wrestling.

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Not this time.

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Another latecomer.

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A female.

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Could she be the one?

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Sometimes being late can pay off.

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After all his efforts, the male is
not going to let this chance

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slip through his fingers.

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This is the cedar forest of the
Atlas Mountains, in North Africa.

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These Barbary macaques enjoyed
a summer of plenty,

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but now they're paying the price.

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Winter here can be brutal.

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In some years,
over half the group perish.

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But in this macaque society,

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the more social the monkey,

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the more likely it is to survive.

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Keeping warm by huddling
can make all the difference.

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But they can't huddle all day.

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They must, eventually, break apart
to feed.

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They spread out, searching for food.

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But each night, the group return
to huddle in the cedar trees.

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No-one wants to be left out.

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Especially the infants.

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This baby, somehow,
has got separated.

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He must get back to the life-saving
warmth of the huddle,

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and soon.

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But there is an obstacle.

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A grumpy male is giving the baby
a rather cold shoulder.

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Maybe a more subtle approach.

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The male decides to leave.

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At last...

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..an enthusiastic reception.

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The male has had less luck.

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It could be a long night.

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Huddling might seem a simple
expression of affection,

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but among these macaques
it's essential for survival.

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And not just here.

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5,000 miles away,
in the forests of Mexico,

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monarch butterflies, in millions,

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also huddle for survival.

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All of them have travelled across
North America

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to escape the winter that
is coming there.

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This forest,
at an altitude of 3,000 metres,

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might seem to offer little
comfort...

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..for temperatures here can drop
below freezing,

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and that could kill the butterflies.

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But in fact,
a thin layer of warm air

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trapped by the tree canopy
protects them,

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and will do so throughout
the winter...

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..provided that the forest
remains undisturbed.

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Unpredictable extremes
of weather, however,

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can disrupt this delicate balance.

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Strong winds can push deep into
the forest, chilling the air.

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Hundreds of thousands
of butterflies

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may be blown from the branches.

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In some years, storms kill 75%
of hibernating monarchs.

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This one has survived...

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..but on the ground.

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And night-time frosts are fatal.

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It can't stay here and live.

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It is too cold to fly,

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but it must get back into
the tree branches somehow.

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So it starts to climb.

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It's the equivalent of a human
climbing up a skyscraper.

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Safety, at last.

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As spring returns,

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the monarchs wake from their
long slumber.

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And now starts one of the Earth's
greatest natural spectacles.

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But this mass awakening
is under threat.

200
00:30:10,370 --> 00:30:15,090
The changing climate is creating
more extreme weather,

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00:30:15,090 --> 00:30:18,170
and storms are becoming
more frequent.

202
00:30:20,530 --> 00:30:25,410
But, for now, this miracle
of nature continues.

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Fire.

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Unpredictable and destructive.

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00:30:51,490 --> 00:30:55,490
This is South Africa's fynbos.

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00:30:55,490 --> 00:30:59,170
Botanically one of the most
diverse habitats on Earth...

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..with over 8,000 different
plant species.

208
00:31:06,610 --> 00:31:08,890
Yet, every two decades,

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00:31:08,890 --> 00:31:12,130
fire reduces the vegetation
to ashes.

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00:31:19,850 --> 00:31:21,970
This may seem catastrophic.

211
00:31:23,170 --> 00:31:27,730
But just days later,
plants burst into life...

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..and transform the landscape.

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00:31:34,170 --> 00:31:38,570
Seeds and bulbs have been waiting
for this event.

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00:31:46,170 --> 00:31:50,370
90 million years of evolution
alongside fire

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00:31:50,370 --> 00:31:53,850
has made some plants
so closely adapted

216
00:31:53,850 --> 00:31:58,090
that they can't germinate
without the presence of smoke.

217
00:32:05,330 --> 00:32:10,890
Remarkably, around 50% of planet
Earth's terrestrial habitats

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00:32:10,890 --> 00:32:14,210
depend on fire to remain healthy.

219
00:32:21,050 --> 00:32:25,730
In Northern Australia, these
savannahs need seasonal fires

220
00:32:25,730 --> 00:32:30,010
to keep them open and prevent the
spread of the nearby forest.

221
00:32:34,090 --> 00:32:37,170
And they are a vital habitat

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00:32:37,170 --> 00:32:39,850
for this colourful resident.

223
00:32:45,490 --> 00:32:49,170
The rare golden-shouldered parrot.

224
00:32:51,490 --> 00:32:54,810
He and his lifelong partner..

225
00:32:54,810 --> 00:32:59,610
rely on grassland for both food...

226
00:32:59,610 --> 00:33:01,970
..and a nest site.

227
00:33:03,490 --> 00:33:08,170
As usual, they've laid their eggs
in a hole in a termite mound.

228
00:33:11,770 --> 00:33:15,170
And now there are four chicks.

229
00:33:17,770 --> 00:33:22,370
The thick mud walls don't only
protect chicks from predators,

230
00:33:22,370 --> 00:33:26,610
but insulate them from the heat
of the scorching sun.

231
00:33:33,130 --> 00:33:36,290
With fledging just days away,

232
00:33:36,290 --> 00:33:38,850
the parents are working overtime.

233
00:33:41,650 --> 00:33:45,290
They collect thousands of seeds
every day.

234
00:34:07,330 --> 00:34:10,050
But they have a problem.

235
00:34:18,010 --> 00:34:22,170
The fire season is becoming
more irregular.

236
00:34:40,290 --> 00:34:43,450
If they are not ready to fly,

237
00:34:43,450 --> 00:34:46,370
chicks have no escape.

238
00:35:10,210 --> 00:35:14,930
But choosing to nest in a termite
mound has a surprise benefit.

239
00:35:16,810 --> 00:35:20,570
Their home is fireproof.

240
00:35:31,290 --> 00:35:37,330
Concrete-like walls keep chicks safe
from the flames outside.

241
00:35:46,330 --> 00:35:50,090
The seeds of fire grass are now
easier for the parrots

242
00:35:50,090 --> 00:35:53,530
to find on the blackened earth...

243
00:35:53,530 --> 00:35:56,690
..and they are the parrots'
favourite food.

244
00:36:04,970 --> 00:36:09,730
So, for both adults and
their fledgling chicks...

245
00:36:10,930 --> 00:36:14,210
..fires are essential for survival.

246
00:36:21,650 --> 00:36:24,650
But their grassland home
is shrinking,

247
00:36:24,650 --> 00:36:29,330
and only about 1,000 of these
lovely parrots still survive.

248
00:36:31,250 --> 00:36:35,730
It's through the active
management of fire by humans

249
00:36:35,730 --> 00:36:39,370
that their world now exists at all.

250
00:36:44,890 --> 00:36:49,610
Humans are affecting habitats
across planet Earth.

251
00:36:49,610 --> 00:36:52,010
For wildlife, all too often,

252
00:36:52,010 --> 00:36:55,250
the consequences have
been disastrous.

253
00:37:03,930 --> 00:37:07,850
Elephants are among the most
tolerant of animals.

254
00:37:10,810 --> 00:37:13,450
They are very long-lived,

255
00:37:13,450 --> 00:37:18,050
and knowledge passed between
generations enables them

256
00:37:18,050 --> 00:37:21,370
to find food and little-used
sources of water in times

257
00:37:21,370 --> 00:37:24,010
of great environmental stress.

258
00:37:26,170 --> 00:37:28,490
But even among elephants,

259
00:37:28,490 --> 00:37:31,690
survival strategies are now
beginning to fail.

260
00:37:38,770 --> 00:37:43,010
In Amboseli, Kenya,
years of extreme weather,

261
00:37:43,010 --> 00:37:46,610
combined with overgrazing
by domestic cattle,

262
00:37:46,610 --> 00:37:50,890
are turning these grasslands
to dust.

263
00:38:19,450 --> 00:38:22,850
This matriarch is over
40 years old...

264
00:38:24,810 --> 00:38:26,690
..and she's already survived

265
00:38:26,690 --> 00:38:29,690
some of East Africa's
worst droughts.

266
00:38:32,850 --> 00:38:37,250
But this year, food is in extremely
short supply...

267
00:38:40,170 --> 00:38:43,410
..and her family are struggling
to find enough.

268
00:38:50,890 --> 00:38:55,010
Her youngest son is malnourished
and weak...

269
00:39:00,130 --> 00:39:03,530
..and is lagging behind his mother
and brother.

270
00:39:12,370 --> 00:39:17,130
She leads them to a pocket of acacia
forest that she knows well.

271
00:39:23,330 --> 00:39:26,610
But broken branches and fallen trees

272
00:39:26,610 --> 00:39:30,130
show that other elephants
have already been here.

273
00:39:34,970 --> 00:39:37,730
There is very little left
worth eating.

274
00:39:44,810 --> 00:39:49,610
Without food, his mother cannot
produce enough milk.

275
00:39:53,890 --> 00:39:55,650
She has no choice...

276
00:39:58,690 --> 00:40:01,250
..but to leave her weakening calf...

277
00:40:02,890 --> 00:40:05,930
..and try to find food elsewhere.

278
00:40:12,210 --> 00:40:18,370
So, she and her elder son
head off...

279
00:40:18,370 --> 00:40:20,650
..without him.

280
00:40:43,970 --> 00:40:47,450
He can only hope for their return.

281
00:41:21,450 --> 00:41:26,050
But for him, time has run out.

282
00:42:01,130 --> 00:42:04,450
There is nothing his mother,
or anybody,

283
00:42:04,450 --> 00:42:07,250
could have done to save him.

284
00:42:18,850 --> 00:42:22,010
With her elder son still alive,

285
00:42:22,010 --> 00:42:24,690
there is hope for her family.

286
00:42:26,530 --> 00:42:30,770
But only if they can adapt quickly.

287
00:42:41,130 --> 00:42:44,770
Some families are proving
to be resilient.

288
00:42:49,810 --> 00:42:53,610
They're travelling long distances,
away from Amboseli...

289
00:42:56,810 --> 00:43:01,130
..and finding new sources
of food and water.

290
00:43:18,570 --> 00:43:21,570
And despite the drought...

291
00:43:25,410 --> 00:43:28,410
..calves are being born.

292
00:43:47,210 --> 00:43:50,210
But given the pace of change

293
00:43:50,210 --> 00:43:52,570
and the challenges they face...

294
00:43:53,930 --> 00:43:58,050
..how many of Africa's elephants
will be able to adapt?

295
00:43:59,090 --> 00:44:02,530
And can they do so fast enough?

296
00:44:16,930 --> 00:44:19,170
The Gobi Desert.

297
00:44:21,730 --> 00:44:25,810
A land of sand and snow.

298
00:44:30,330 --> 00:44:34,250
For at least a million years,
this has been

299
00:44:34,250 --> 00:44:38,210
one of the most extreme habitats
on Earth.

300
00:44:42,690 --> 00:44:45,530
Yet, footprints in the sand

301
00:44:45,530 --> 00:44:49,010
reveal that there is life here.

302
00:44:55,530 --> 00:44:57,450
A snow leopard.

303
00:44:57,450 --> 00:45:00,010
Seldom seen...

304
00:45:01,330 --> 00:45:06,450
..especially in such hot,
arid conditions.

305
00:45:10,530 --> 00:45:14,810
They live up to 2,000 metres
above sea level,

306
00:45:14,810 --> 00:45:18,850
and patrol vast territories.

307
00:45:47,290 --> 00:45:50,250
They are rarely seen together.

308
00:45:58,090 --> 00:45:59,490
A mother...

309
00:46:02,690 --> 00:46:05,050
..with cubs.

310
00:46:07,250 --> 00:46:10,090
Filmed here for the first time

311
00:46:10,090 --> 00:46:12,890
in such intimate detail.

312
00:46:20,930 --> 00:46:24,330
And they give us a glimpse
of their family life...

313
00:46:25,370 --> 00:46:27,330
..such as it is.

314
00:46:43,890 --> 00:46:47,250
Snow leopard cubs stay
with their mothers

315
00:46:47,250 --> 00:46:51,130
longer than those of almost
any other big cat.

316
00:46:56,930 --> 00:47:00,930
They remain together for over
two years...

317
00:47:03,810 --> 00:47:08,610
..as they learn how to master
the extremes.

318
00:47:16,010 --> 00:47:20,410
Which they do so well
that they are able to thrive

319
00:47:20,410 --> 00:47:24,370
in some of the hottest, coldest...

320
00:47:24,370 --> 00:47:27,250
..and highest places on Earth.

321
00:47:38,570 --> 00:47:42,450
Some animals,
over millions of years,

322
00:47:42,450 --> 00:47:46,610
have evolved ways of surviving
extremely hostile conditions.

323
00:47:49,650 --> 00:47:53,970
But as the extremes become
more extreme...

324
00:47:53,970 --> 00:47:58,170
..evolution is being outpaced.

325
00:48:06,090 --> 00:48:10,450
These extraordinary places
are still inhabited

326
00:48:10,450 --> 00:48:12,890
by some of Earth's most resilient

327
00:48:12,890 --> 00:48:15,050
and adaptable species.

328
00:48:18,250 --> 00:48:20,570
But in our rapidly changing world...

329
00:48:22,050 --> 00:48:27,010
..this is planet Earth as
you may never see it again.

330
00:48:50,610 --> 00:48:53,530
 The most
extreme parts of our planet

331
00:48:53,530 --> 00:48:56,170
are not always found where
you might expect.

332
00:48:59,130 --> 00:49:03,130
Hidden deep in the forests
of Vietnam, a local man,

333
00:49:03,130 --> 00:49:06,450
Mr Ho Khanh, made an extraordinary
discovery.

334
00:49:26,050 --> 00:49:28,050
He didn't know it at the time,

335
00:49:28,050 --> 00:49:32,450
but he had stumbled upon arguably
the largest cave in the world.

336
00:49:44,690 --> 00:49:48,490
Inspired by Mr Ho Khanh's discovery,

337
00:49:48,490 --> 00:49:52,610
the Planet Earth team set out
to film Hang Son Doong.

338
00:49:54,690 --> 00:49:56,810
But first, they have to get there.

339
00:49:58,210 --> 00:50:00,490
We've left the river valley,

340
00:50:00,490 --> 00:50:02,930
and we're walking uphill now
to the entrance.

341
00:50:02,930 --> 00:50:04,970
It's just thick, thick forest.

342
00:50:06,690 --> 00:50:09,930
After trekking for two
gruelling days,

343
00:50:09,930 --> 00:50:12,770
the team finally arrive.

344
00:50:12,770 --> 00:50:16,130
Down here is the entrance
to Hang Son Doong,

345
00:50:16,130 --> 00:50:19,690
this tiny opening in this
massive jungle.

346
00:50:19,690 --> 00:50:22,650
It's amazing that anyone
ever found this place.

347
00:50:25,730 --> 00:50:28,490
We're about to go in for
the next 18 days,

348
00:50:28,490 --> 00:50:31,090
and it's lights on from here on out.

349
00:50:32,770 --> 00:50:36,250
Local experts guide the team
through the darkness.

350
00:50:37,490 --> 00:50:39,930
OK, I can go? Yes, yes.

351
00:50:49,570 --> 00:50:51,130
I'm good. I'm OK.

352
00:50:51,130 --> 00:50:52,810
It's just really slippery.

353
00:50:54,770 --> 00:51:00,290
A complex system of ropes leads
them down a 90-metre descent.

354
00:51:05,490 --> 00:51:07,050
OK.

355
00:51:07,050 --> 00:51:08,330
Thanks.

356
00:51:12,250 --> 00:51:15,050
After four hours clambering
over rocks...

357
00:51:17,050 --> 00:51:19,970
...they finally reach what
will be their camp.

358
00:51:28,730 --> 00:51:31,930
The team wake to a new day -

359
00:51:31,930 --> 00:51:33,890
but in darkness.

360
00:51:33,890 --> 00:51:35,650
How did you sleep, Luke?

361
00:51:35,650 --> 00:51:37,730
Quite tired.

362
00:51:37,730 --> 00:51:40,050
These are all of the tents
behind me.

363
00:51:40,050 --> 00:51:43,610
You can see they are pretty...

364
00:51:43,610 --> 00:51:45,050
..pretty snug.

365
00:51:45,050 --> 00:51:48,290
This is where we have our breakfast
every day,

366
00:51:48,290 --> 00:51:50,570
made by some amazing cooks.

367
00:51:52,010 --> 00:51:54,170
This is our charging station.

368
00:51:54,170 --> 00:51:56,570
Batteries for camera equipment,
batteries for our lights,

369
00:51:56,570 --> 00:51:58,730
our head torches,
which are so important.

370
00:51:59,770 --> 00:52:02,610
This is our water station.

371
00:52:02,610 --> 00:52:05,850
Everything that we have got has been
brought in by someone,

372
00:52:05,850 --> 00:52:08,650
so you can't shower or wash.

373
00:52:08,650 --> 00:52:10,930
And it's not just water.

374
00:52:10,930 --> 00:52:15,610
Tonnes of equipment has had to be
carried into the cave,

375
00:52:15,610 --> 00:52:17,930
every inch of the way.

376
00:52:21,090 --> 00:52:24,490
Now deep underground,
the powerful lights

377
00:52:24,490 --> 00:52:26,810
reveal just how vast this cavern is.

378
00:52:28,250 --> 00:52:29,930
That is amazing.

379
00:52:29,930 --> 00:52:31,370
Look at that. It's...

380
00:52:31,370 --> 00:52:33,170
It's huge!

381
00:52:35,610 --> 00:52:37,890
As you turn on each of the lights,

382
00:52:37,890 --> 00:52:40,730
another part of this enormous
chamber is revealed.

383
00:52:43,450 --> 00:52:46,450
It's magic. Absolutely magic.

384
00:52:49,650 --> 00:52:52,770
To try and capture the true scale,

385
00:52:52,770 --> 00:52:56,650
the team attempt a filming technique
never tried before.

386
00:52:57,890 --> 00:53:01,210
We're trying to do a little bit
of a dance with the drones,

387
00:53:01,210 --> 00:53:05,330
whereby we have one drone sort
of slightly below the other,

388
00:53:05,330 --> 00:53:09,450
one filming the other one lighting
a feature in the cave.

389
00:53:09,450 --> 00:53:11,770
It's a really tight space.

390
00:53:11,770 --> 00:53:13,850
You can't see anything.

391
00:53:13,850 --> 00:53:15,770
What could go wrong?

392
00:53:19,490 --> 00:53:21,290
OK, slow down a bit.

393
00:53:22,890 --> 00:53:24,970
It's making everyone a little
nervous.

394
00:53:26,090 --> 00:53:28,690
Yeah, don't go up any higher, Luke.

395
00:53:31,050 --> 00:53:33,370
OK, that's a nice height.

396
00:53:36,970 --> 00:53:40,250
With one drone lighting
and one drone filming...

397
00:53:42,050 --> 00:53:47,130
..they reveal the wonder of some of
the world's largest stalagmites.

398
00:53:56,050 --> 00:53:59,170
As the days pass,
the team settle into

399
00:53:59,170 --> 00:54:02,410
the everyday routine of
life underground.

400
00:54:03,610 --> 00:54:07,850
This is the epitome of
being off-grid.

401
00:54:07,850 --> 00:54:09,970
We call that one seesaw loo

402
00:54:09,970 --> 00:54:12,490
because it's kind of on a rock,

403
00:54:12,490 --> 00:54:15,130
and every time you sit on it
and lean back,

404
00:54:15,130 --> 00:54:19,050
you're scared that there's
going to be a disaster.

405
00:54:20,690 --> 00:54:24,130
The strangest thing is
having no connection

406
00:54:24,130 --> 00:54:26,210
to the outside world whatsoever.

407
00:54:26,210 --> 00:54:29,690
Time is warped.
Nothing makes sense underground.

408
00:54:34,290 --> 00:54:38,450
Without daylight to guide them,
the team work round the clock

409
00:54:38,450 --> 00:54:41,450
to capture the cave's most
unique features.

410
00:54:43,130 --> 00:54:45,410
Most special of all,

411
00:54:45,410 --> 00:54:49,050
an event which happens only
a few weeks a year.

412
00:54:51,770 --> 00:54:54,210
To get there, they must navigate

413
00:54:54,210 --> 00:54:56,890
through boulder fields
and tight squeezes.

414
00:55:06,370 --> 00:55:09,010
Here, around half a million
years ago,

415
00:55:09,010 --> 00:55:11,250
the cave roof collapsed,

416
00:55:11,250 --> 00:55:13,970
opening a window to
the outside world.

417
00:55:18,370 --> 00:55:21,250
The team wait for
just the right conditions.

418
00:55:22,610 --> 00:55:25,210
We've been sat here for hours.

419
00:55:25,210 --> 00:55:27,770
And finally, just on the
right-hand side of the wall,

420
00:55:27,770 --> 00:55:30,290
we can see the first signs of light.

421
00:55:34,210 --> 00:55:36,570
After weeks of darkness

422
00:55:36,570 --> 00:55:38,450
200 metres underground...

423
00:55:39,770 --> 00:55:41,610
..they see sunlight

424
00:55:41,610 --> 00:55:43,970
illuminate the cave floor.

425
00:55:49,010 --> 00:55:53,850
The way it just lights up
this massive cave...

426
00:55:53,850 --> 00:55:57,250
..when we've been trying to do it
with about four or five lights

427
00:55:57,250 --> 00:56:00,690
and barely even lighting
the smallest section.

428
00:56:00,690 --> 00:56:02,610
When the sun comes in, it just...

429
00:56:06,290 --> 00:56:08,330
I think everyone's got goose bumps.

430
00:56:12,650 --> 00:56:17,450
I don't think I've ever appreciated
sun so much in my life.

431
00:56:19,050 --> 00:56:21,090
It's incredible.

432
00:56:23,810 --> 00:56:26,850
Look at the backlit waterfalls.

433
00:56:26,850 --> 00:56:29,490
They're so slow coming down.

434
00:56:29,490 --> 00:56:32,290
It's literally one of the best
things I've ever seen.

435
00:56:35,810 --> 00:56:39,730
For the crew, the sunbeam
marks a profound end

436
00:56:39,730 --> 00:56:42,050
to their time in the cave.

437
00:56:45,330 --> 00:56:47,610
We're outside!

438
00:56:47,610 --> 00:56:50,610
It's so green, it's so bright.

439
00:56:50,610 --> 00:56:54,570
Being back above ground feels like
where we belong.

440
00:56:56,530 --> 00:56:59,850
It's a wonder to imagine
what other extremes

441
00:56:59,850 --> 00:57:04,250
still lie beneath the surface
of planet Earth.

442
00:57:12,690 --> 00:57:15,010
Next time...

443
00:57:15,010 --> 00:57:17,250
..the human world...

444
00:57:22,890 --> 00:57:27,810
..where animals must find
new ways to survive...

445
00:57:28,930 --> 00:57:30,890
..amongst us.

446
00:57:37,570 --> 00:57:41,290
Habitat Explorer brings animals
and their habitats to life.

447
00:57:41,290 --> 00:57:44,610
Explore this free interactive,
and make origami animals.

448
00:57:44,610 --> 00:57:48,490
Go to bbc.co.uk/planetearth3

449
00:57:48,490 --> 00:57:51,050
and follow the links to
the Open University.

450
00:57:51,050 --> 00:57:54,530
Or to order a free printed version,
visit the website

451
00:57:54,530 --> 00:57:57,010
or call the numbers on the screen.