lies the Necropolis of Saqqara.

Today, Egyptologist Chris Naunton travels here

to investigate what triggered over a thousand

years of pyramid building.

He's been granted rare access to explore restricted areas

of this necropolis.

This is a pretty exciting moment for me

because I've never been inside before.

NARRATOR: This ancient cemetery is home to 11

pyramids and hundreds of tombs.

But one structure dominates all others,

the first pyramid ever built.

This is where it all began.

It is the first monumental building

in stone anywhere in the world.

NARRATOR: Constructed more than 4,500 years ago,

this is the step pyramid tomb of Pharaoh Djoser, a King

of Egypt's third dynasty.

It's a revolutionary masterpiece designed by Egypt's

pioneer architect, Imhotep.

His achievement was massive not just for the Egyptians,

but for humankind.

[grandiose music]

NARRATOR: Born as a commoner, Imhotep

rose to become Pharaoh Djoser's trusted advisor and eventually

his chief architect.

He invented the stepped pyramid using

stone blocks instead of mud bricks,

allowing him to build ever bigger.

More than 2,000 years after Imhotep's death,

he was worshipped as a god all the way

up to Greek and Roman times.

Chris wants to discover for himself

what inspired Imhotep to design his groundbreaking step

pyramid.

He climbs to higher ground to examine

the shape of older burial structures that surrounded.

They're called mastabas.

And they are these sort of squat, square platforms,

slightly sloping, inwardly inclining walls.

NARRATOR: Chris can make out traces

of these simple structures within Imhotep's design.

Now that we're getting closer to the pyramid,

you can really see this series of platforms, one

on top of another.

So the bottom one, in some sense, is a mastaba.

It's just the addition of these successive layers

that make it into a pyramid.

And it's an incredible achievement, architecturally.

NARRATOR: Built from over 500,000 tons of limestone,

constructed in the mastaba-style layers,

the step pyramid stands over 200 feet high,

then the tallest building in the world.

Its impact on the ancient Egyptian landscape was huge.

10 more kings replicated Imhotep's design,

determined to attain the same status as the pharaoh

of the first pyramid.

Their tombs became some of the most iconic sacred buildings

on the planet, each growing the necropolis until it stretched

5 miles across the desert to create

a sprawling city of the dead.

Today, Imhotep's masterpiece still

dominates the Egyptian desert.

But while his structures survive, no trace of the man

himself has ever been found.