In ancient times,

they were used to mark the entrances of houses and they soon became

a sign of joy and festivity.

At Chinese New Year, lanterns represent the light of hope.

Back in the 1960s, the people of Harbin couldn't afford traditional

lanterns to celebrate New Year,

so they froze water in buckets, put candles inside,

and the ice Festival was born.

Using light as a symbol of celebration has continued through

to the modern festival today.

Almost every one of over 2,000 buildings here

has its very own light display.

The lighting design is almost as epic an endeavour as building the

festival itself.

The logistics involved in making this happen are staggering.

The sheer scale of the operation

means the Festival needs 230,000 metres of electrical cables.

That's 13.8 million individual lights.

But creating such a vast electrical system demands meticulous attention

to detail to withstand such extreme conditions.

And this is how they do it.

The lights are actually individual LEDs

housed within a resilient silicon strip.

These aren't your standard household LEDs.

A team of engineers have specifically designed ones

to withstand the freezing temperatures.

OK, it's more expensive than a conventional light bulb,

but it is more eco-friendly. Plus, can you imagine

the bill to pay the electricity at this place?

Each block of the ice is hand chiselled to create a groove

for the LED strip.

The blocks are then lined up in a brick wall pattern.

The great thing about LEDs is they emit less heat.

What you don't want within an ice block is a block melting.

Now, you need to join the bricks together. Traditionally,

and especially in your home, you'd use something like cement.

But here in Harbin they use something completely different.

Water. I've kept it in my coat to try and keep it liquid.

Very simply, pour the water on,

and I literally only have a few seconds to get the next brick on top

before the water freezes.

The idea being that those two then fuse together and it becomes a solid

structure. A bit more Harbin cement...

Now the moment of truth. Hook some batteries up to my LEDs

and in theory I'll be able to illuminate

this beautiful piece of work.

Of course, there's a slightly bigger switchbox for the main event.

Each individual light is painstakingly turned on by hand,

row by row,

building by building, and I get to turn on the very last building.

So, which switch is it? This one here?

Three, two, OK!

There it is. A little bit of Russia in the middle of China.

The ice city is developed across an entire year by a team of architects,

and lasts just three months.

This is the chief designer.

How does it make you feel that

everything that you've created here is gonna melt?