Engineering Secrets of the Lion Gate

This stone gate in Greece has stood for 3,300 years.

It's the Lion Gate of Mycenae, and above the doorway is a triangular hole,

left hollow on purpose.

The walls are built from boulders no person could lift,

5 to 20 tons each,

stacked with no mortar at all.

In places they're over 25 feet thick.

Later Greeks couldn't believe humans built this.

They decided only the Cyclopes, one-eyed giants could have stacked such stones.

That's why we still call these Cyclopean walls.

But the gateway was the problem.

To open a doorway and keep the wall rising above it,

they laid a single 20-ton stone across the top.

Then hundreds of tons piled on it.

Here's the catch.

Stone is strong when squeezed, but weak when bent.

All that weight on the middle would snap the lintel in two.

A thicker stone only adds weight that breaks itself.

Why not build an arch?

Because the keystone arch wouldn't be invented for more than another thousand years.

These builders had to solve it without one.

So they flipped the idea.

Instead of bearing the weight, they gave it a path around the stone.

Above the lintel, they stepped each wall layer inward until both sides met at the top.

Now the hundreds of tons flow down the triangle's sides into the ground, and the lintel carries only its own weight.

The hollow was filled with a light slab carved with two lions.

The same trick holds up a nearby tomb, where a single lintel weighs 120 tons.

Five heavy trucks.

Through three thousand years of earthquakes,

weight dodged a thousand years before the arch.