How big is
the Great Pyramid?

The full narration of the video.

The pyramid isn't as tall as a skyscraper, but it's far heavier. We mean the biggest one in Egypt, the Great Pyramid of Khufu, finished some 4,500 years ago. Start with height. When new, it stood 146 metres, about a 50-storey building.

Today the Burj Khalifa reaches over 800 metres, more than five times as tall. Yet for more than 3,800 years, nothing built by people stood taller. Now look at the ground. Its base is a square, 230 metres on each side.

That's more than seven football pitches, and a walk around it is almost a kilometre. The truly staggering part is how heavy it is. The whole pyramid weighs about six million tonnes. And the Burj Khalifa? Half a million, one twelfth as much.

A fifth of the height, yet twelve times the weight. Why? Think of moving boxes. An empty box looks big, but one hand lifts it. Fill the same box with books, and two people can't budge it.

A skyscraper is the empty box: floor after floor of rooms, mostly air. The pyramid is the box full of books. From bottom to top it's almost solid stone, with just a few narrow passages and small rooms inside. The books are the stone blocks. Those steps you see in photos are the edges of the blocks.

How big is one block? On average over two tonnes, heavier than a small car. And there are about 2.3 million of them. It took roughly twenty years to build. Spread 2.3 million blocks over twenty years, and that's over 300 blocks a day.

With ten-hour working days, that's one block set about every two minutes. Where did all that stone come from? A work diary from that time records exactly this: moving stone. Its writer was a crew leader. His boat crew carried white limestone from across the river, two or three trips every ten days.

That white stone was the outer casing, making the pyramid gleam in the sun. Later the casing was stripped away and the tip was lost; today it stands eight metres shorter. And the builders weren't slaves, but thousands of paid craftsmen and labourers.

So the pyramid's size isn't about height, it's about weight: a small mountain, stacked by hand, one block at a time. But one thing is still unsettled: how did two-tonne blocks get over 100 metres up? Some say a long straight ramp, others say a ramp that spiralled up around the pyramid.

Straight or spiral, which one do you bet on?