This is not a science fiction movie.
It's right here on Earth.
This underground sanctuary
is as beautiful as it is deadly.
So don't get too distracted
by the giant crystals.
You will suffocate in a matter of minutes.
Miners discovered
the Naica crystal cave in 2000,
while they had been searching
for fresh ore deposits
in Chihuahua, Mexico.
The cave sits at a depth
of nearly 300 m (984 ft),
and was filled with mineral-rich waters,
which they had to drain.
They found enormous beams
of gypsum crystals,
some of them measuring
about 11 m (36 ft) high.
But with the temperature
reaching 50 °C (122 °F)
and a humidity level of 90%,
this wonder is a death trap.
Since the cave is closed off from tourists,
the only people who have seen it
are a handful of miners and researchers.
But if you managed to get in there,
how could you survive?
First, you'll have to travel
to the Chihuahuan Desert
and make sure the cave has been drained.
The mine staff
will have to give you permission
and supervise you throughout your stay.
You'll have to undergo a medical check
to make sure you're fit enough
to withstand the cave’s climate extremes.
Don't venture into the cave
if you have high blood pressure,
heart or respiratory conditions.
The heat can aggravate all of these
and put you at risk of dying.
You have only 10 to 15 minutes
before you enter the physical danger zone.
The humidity in the cave
can reach almost 100%.
When you breathe in air that is warmer
than your body temperature,
this cools the humid air
and condenses it into liquid.
This means that fluid
can build up in your lungs.
You may have difficulty breathing,
lose consciousness
and choke to death.
There's a specially designed cooling suit
that contains a respirator
and provides you with
chilled breathable air.
Using the special suit,
you can stay about 60 minutes.
As the special sealing doors finally open,
your adventure begins.
Watch your feet and move slowly
as the cave is slick with condensation.
One wrong move
and you could fall face-first
on gypsum spears.
Always steer clear of really huge
columns of gypsum.
They are a beautiful sight
but they can be unstable.
A giant 5 ton crystal falling on top of you
would be
literally crushing.
Plan your route to be
as efficient as possible.
Especially if you're collecting samples
or carrying extra gear.
Too much movement
can quickly tire you out,
even if you're wearing a suit.
If you begin to feel fatigued
or slightly faint,
leave the cave immediately.
If you lose consciousness and fall,
you could get hurt by some sharp crystals,
or get trapped and cooked to death.
A rescue mission could put
everyone involved in danger.
After leaving the cave,
you’ll have to get your heart rate and vitals
checked again by a doctor.
You'll probably have a really fast heart rate
which will gradually return to normal
once you hit the fresh air.
You survived this beautiful
but deadly cave.
But this is just one of many
natural wonders on the planet
that could kill you.
Would you like to visit a boiling lake?
What about an island full of snakes?
Discover the deadliest places on Earth,
right here.