Horizon (1964) s38e06 Episode Script

On one terrible night 2,500 years ago the entire Greek city of Helike and all of its people were swept beneath the sea.
The catastrophe inspired one of the greatest stories of all time, the myth of Atlantis.
The story has launched a thousand searches, but until recently the real city of Helike and all its lost treasures have lain hidden.
This is the tale of a small band of scientists and their quest to find the real Atlantis - the lost city of Helike.
This is the coast of Greece on the Corinthian Gulf 150km west of Athens.
It is one of the most active earthquake regions in the world and its violent past holds a mystery that has captivated archaeologists for decades, for according to old Roman texts there was once a great ancient Greek city here called Helike.
2,500 years ago Helike was a thriving metropolis.
Over five thousand people lived and worked within its walls and pilgrims thronged to its Temple of Poseidon, god of earthquakes and the sea.
Helike was the religious centre of this region and people from many other parts, not only from this region, came to worship Poseidon here.
Pilgrims came to pray for protection against the elements, but on one cold winter's night in 373 BC the god of earthquakes and the sea turned on his own people.
The ancient sources said the earthquake struck at night when most people were caught in their houses.
A massive tidal wave,a tsunami or sea wave came in and swept away all survivors.
According to ancient texts, Helike and all of its people were swept to the bottom of the sea never to be seen again.
So great was the tragedy experts think it inspired one of the greatest of all myths.
Just a few, short years after the disaster the Greek writer Plato created the story of Atlantis, the legendary city swept beneath the waves.
So Helike was the only city to disappear without a trace in one night, so if there's a grain of truth at all to the story of Atlantis it's the disappearance of Helike which inspired in Plato to write the myth of Atlantis.
And just like the mythical Atlantis Helike has remained hidden ever since, its location a mystery.
All archaeologists knew was that the city should lie hidden somewhere beneath the Corinthian Gulf, but no one knew where.
The tale of the missing city has fascinated archaeologist Dora Katsonopoulou and physicist Steven Soter for decades.
Well over, over, certainly over two metres.
Over two metres.
Because there is… As tall as a person? As tall yes… Dora grew up by the Corinthian Gulf surrounded by stories of the great lost city right on her doorstep.
When I was a child I heard a lot of stories about this famous lost city.
These stories that make the imagination of a child grow wild.
For hidden beneath the waves should lie an entire city from the heyday of Ancient Greece, a time whose art, philosophy and politics would shape the whole of Western civilisation.
It's a time capsule from the golden age of Greece, from classical Greece.
It will have preserved in it everything that would, that would last in an environment like that - the tools, the artefacts, the, the pottery, the stones, the inscriptions, the coins, many organic remains.
It will tell us a great deal about life in a classical city of this time and we do not have a site like this anywhere else in the world in which this much material could be preserved.
Helike could given an unique chance to see how the people who founded our civilisation actually lived.
The houses they lived in and the marketplace they shopped in.
It could be a snapshot of daily life frozen in time.
But for years there was almost no trace of Helike.
All there was was one tiny clue.
There is a coin which is inscribed with the name of Helike and it has a head of Poseidon on one side and a trident and dolphins on the other and it's of a fine classical type and this coin was found by local people.
This was the physical evidence that Helike really existed.
That one coin has inspired a search that has lasted for over a century.
The most important thing in this area to be found some day is this famous city.
For me it is a scientific challenge and a dream which one day might come true, but finding Helike is a very difficult problem for Greek archaeologists.
For this is the mystery of Helike.
Even though no one doubts that it exists, just like Atlantis, Helike has always eluded those who have searched for it.
One of the most famous people to look for Helike was the great technological genius, Professor Harold Edgerton.
Edgerton's inventions transformed the way we see the world.
He was one of the first to film things in slow motion, one of the first to use strobe lights in photography and one of the first to use sonar to take pictures of the sea floor.
We always do this test before we go out to sea.
The interpretation of these marks when you put out to sea should tell you where the shipwrecks are and rocks, mud, sand and other things.
Edgerton was convinced that with his technology for seeing underwater finding Helike would be simple.
For the ancient texts told you exactly where to look.
The texts say the lost city lay seven kilometres from Aigion to the east.
The town of Aigion still exists today.
It lies 150 kilometres west of Athens on the coast of the Corinthian Gulf.
Seven kilometres east of Aigion brings you to the sea and this is where Edgerton set out to look.
Paul Kronfield was part of the team.
It was the ultimate adventure for a young man that's just fresh out of college thrust out into a new world of science.
A lot of the people there were thinking of some of the treasures of Helike was they certainly are there.
There's, there's certainly a lot of gold, a lot of very valuable things.
They thought the key to finding this treasure would be Edgerton's sonar imaging equipment, his sonar fish.
It works by sending out pulses of high frequency sound which bounce off the seabed.
The returning echo is picked up by the fish and by comparing the time delay between pulse and echo you can build a picture of the sea floor.
Edgerton spent nine years combing the Corinthian sea and just east of Aigion, exactly as the ancient texts predicted, the fish found something intriguing.
As we surveyed there offshore approximately in water depths 140ft that's where we found the pockmarks.
We found holes.
Some of them were configured in straight lines that extended half a kilometre or so.
This is unusual.
This caused a great deal of excitement on the survey boat.
One could imagine this could be the remnants of the city, this could be a street, this could be a foundation.
Edgerton thought he'd found it, the city whose fate had inspired Atlantis.
So in 1973 the Greek government brought in a huge floating drill rig to dig down into the sea floor.
I was hoping we would find gold coins, or artefacts, or something that was definitely manmade that would show that this, this was a city, something that you could definitively and immediately date.
It was 140ft down to the seabed and they drilled 24 hours a day for two weeks, but beneath the holes all they found was mud and gravel.
It wasn't the lost city at all.
Just a strange, natural rock formation.
Edgerton had spent nine years combing the ocean, but for all his technological might the lost city had defeated him.
And there it rested for 15 years.
Helike seemed destined, like Atlantis, to remain a mystery and then in 1988 alone came Dora and Steven.
Their team tried a different approach and went back to the very beginning.
If they could find out what happened on the night of the disaster maybe they could work out where the city was hidden.
In the only evidence available, the ancient texts, Dora discovered something that puzzled her.
One of the texts describes the city as being two kilometres from the sea, but if the city was really that far inland could it have been swept into the sea as everyone thought? Dora thought the answer might be hidden in the meaning of a single Greek word.
The texts say the city was submerged in the poros.
Up until now everyone had assumed poros referred to the sea, but Dora thought differently.
poros means a narrow passage of water so it couldn't be the Corinthian Gulf which, which is a sea.
Instead she thought porosmight refer to an inland stretch of seawater, like a lagoon.
When I went back to the sources and looked at this again I thought that in this area where Helike stood before a lagoon was formed.
So rather than being swept two kilometres into the sea, somehow the inland city had been flooded with seawater where it stood.
The entire area between the city and the sea submerged and was filled with waters, so this must have been the poros, the lagoon that was formed there.
But was this really credible? How could an earthquake make an inland city sink underwater? Dora and Steven needed an earthquake expert.
The man they turned to was Iain Stewart.
Stewart has spent 15 years studying evidence of earthquakes in the region.
He thinks it all comes down to one slab of rock.
This is the Helike fault.
We think this is the fault surface that was probably responsible for the earthquake that destroyed Helike.
We know from an earthquake in 1861 that this fault has one peculiar quality.
It makes the ground sink, or if you could take a cross-section beneath it you would see a giant, sloping crack in the Earth's crust.
This is constantly being pulled apart under immense pressure which builds up until the crust finally breaks.
This releases the massive force of an earthquake which pushes the mountains up and wrenches the plain down.
In 1861 the entire plain was dragged over a metre downwards.
What happens is when the earthquake ruptures up to the surface, when it gets to the surface the whole of the plain that's in front of the fault just drops about a metre and a half.
The other area behind the fault, the actual fault itself rises up.
You can get some idea of the power that's involved in this when you look at some of these scratches.
Now these are scratches that are made in solid rock.
Pebbles have been sticking out, having carved their way down as this grew and so what is happening here is we're getting a, an ancient earthquake just etched into the rock face.
Stewart believes that the same thing happened on that winter's night in 373 BC, but on a much larger scale.
With a huge jolt the plain would have dropped down dragging the city with it, but that was just the beginning because we know from the 1861 earthquake that there was worse yet to come liquefaction.
This bizarre side-effect of earthquakes has only been caught clearly on camera once before, during an earthquake in Japan in 1964.
It starts with what looks like a burst water main, as the intense pressure from below forces water and soil from deep beneath the ground to erupt to the surface.
This weakens the ground soil so much it literally gives way.
The land collapses and the buildings sink downwards.
Stewart believes liquefaction on a massive scale could have occurred at Helike.
I think the most likely thing to have happened in 373 BC is that we had extensive liquefaction in this plain.
We've got large amounts of material getting ejected out of the, the surface as water and sand volcanoes, and then the plain lowering down.
This substance from liquefaction added to the subsidence from the actual fault movement itself is probably enough to take it down several metres.
This would take much of the city below sea level allowing the sea water to flood in, but the final disaster would come when the weakened coast crumbled into the sea.
This would cause a giant wave.
That wave would race across the Corinthian Gulf, ricochet off the opposite coast and return minutes later, crashing over the sunken plain and submerging the city for ever.
All that would have been left of Helike would be a poros, a calm lagoon.
There was just one small problem with this theory.
If Helike is hidden under a lagoon where is the lagoon now? Today the plain is solid land.
How could a body of water big enough to cover a city simply disappear? A clue to what might have happened lay hidden in a lush lemon grove.
Deep in the shade lies an old bridge.
The strange thing about this bridge is that it's a long way from the nearest river.
About 500 years ago the Selinous river bed was at this location.
Today the river runs about 300-400m away from here which means that in the last 500 years the river has moved over a metre per year.
Somehow the river has moved leaving the bridge high and dry, so there is now solid land where there was once water.
What caused this can be found high up in the hills.
These craggy mountains, thrust up by earthquake movement deep within the Earth, have been eaten away over millions of years by the rivers coursing through them, washing rocks and debris down to the Helike plain and it's this sediment coming down to the plain that might explain why there is now solid land where there once might have been a lagoon.
Using a model river at the University of Newcastle geologist thinks he can explain how it happened.
The model can be used to show how sediment is transported by a river and it can show how sediment affects the coastal plain.
When there is just water running through the model the river runs straight, but when sediment is added in the form of sand it is deposited within the river forcing it to change position.
So this provides us with a snapshot of how the Selinous river has behaved through time.
The river is constantly shifting backwards and forwards through time as the sediment is deposited within the river.
It's this sediment that has filled in the land under the bridge, but the material washed down from the mountains has done more than just change the course of the river.
It has changed the whole shape of the plain.
Each winter the rivers are flooded, breaking their banks and depositing sediment across the entire plain.
This has left a new layer of soil which has built up year on year creating new land, so if Helike was submerged beneath a lagoon in the thousands of years that followed, the debris coming down from the mountains would slowly have filled it in creating a solid plain.
It means that Helike, the city that inspired the myth of Atlantis, should lie not underwater but underground.
So, convinced that Helike was hidden somewhere inland, in 1991 Dora and Steven set out to find it, but with no clues where to start they came up with an unusual idea.
They peppered the area with small probes called bore holes, drilling deep into the ground hoping to bring up traces of Helike.
We really had no evidence at the beginning where to look for it on land.
It's an enormous plain, many square miles, so we started drilling us some boreholes in representative places, some nearer the shore, some near the mountains, some in between.
Steven sank most of his life savings into drilling hole after hole across the vast area.
With each sample they searched through the mud looking for any sign of ancient remains, but for two years they found nothing.
Drilling 18 boreholes and not finding it and knowing that it must be there was, I guess it was frustrating.
It was of course frustrating and adding the various other problems it was even more frustrating, so one had to have a lot of patience.
In the end their patience would pay off, but the clues that would lead them to the lost city weren't down on the plain, they were high up in the hills.
Beneath a collection of apparently insignificant stones a local archaeologist had unearthed classical ruins years before.
He thought these might be part of an ancient fortress that texts say stood on the hills above Helike.
If he was right then the lost city might lie directly beneath and there was another clue pointing to the same place.
Up in the hills was a cave with an amazing legend attached to it.
It was said that the people of Helike would come here to leave offerings to the Greek hero Heracles.
According to Pasuanias,who came through here in the 2nd century AD,30 stadia beyond Helike, that's about 5.
5km,there was a cave of Heracles, an oracle of the god, where you could ask a question and tell your future.
Archaeologists have argued over it for years, but if this is the cave of Heracles then it could help pinpoint where the city is hidden.
We think this is the cave of Heracles and if it is, it means that Helike is about 5.
5km somewhere in the plain in that direction.
Together with the seven kilometres distance from Aigion this would give them two reference points to pin down Helike's location.
Now taking these two topographical points, that is the distances from Aigion seven kilometres east and the distance from the cave of Heracles 5.
5 kilometres west, we come to only one area in mid-plain where we should look for Helike and where Helike should have been.
It placed Helike right in the middle of the plain, directly beneath the ancient fortress.
They could now concentrate their search in one small area and soon they found something.
Hidden deep within the long, muddy core they found their first sign of ancient remains.
It was pottery fragments and since pottery fragments and I remember that the whole team was really shouting out and we took a nice picture all together looking at this famous pottery fragment that was the first one to ever be found, so indeed it was a very important moment and gave us the hope that we are in the right track.
They now knew there had to be buried remains somewhere beneath them, but they didn't know what, or even how old, so they called in some high-tech help a magnetometer.
These work by picking up slight variations in the Earth's magnetic field.
This data can be used to build up an image of what lies underground.
The whole procedure took hours of painstaking work, but what it produced was unmistakable.
When I saw the magnetic map for the first time I recognised this is a building, this is not a random pattern that you usually find in a magnetic survey of an area like that.
It really jumped out.
In fact it was the best pattern of magnet, magnetic data that I'd ever seen and we both looked at this and said this must be a building.
Usually it takes a lot of interpretation, but this just jumped out at you.
You can see this linear cross-section.
It looks like a fissure of walls that make right-angles and then assuming some degree… And so they prepared to dig on the plain for the very first time, but before the building could be unearthed there was a terrifying reminder of the disaster that befall Helike.
When the earthquake struck it was about three in the morning.
Of course I was terrified because it was a tremendous noise.
The house was going like this on both sides, then up and down, then all around.
the following morning Dora took her camera out to record the aftermath.
Along the weakened coast large chunks of land had slipped into the sea and in the ground there were clear signs of liquefaction where water and mud had burst up to the surface, but this was just a fraction of what had happened to Helike 2,500 years ago.
The team were badly shaken.
26 people had died in the earthquake, but nonetheless they got on with the dig and just two metres below the surface they uncovered what the magnetometer had seen.
It wasn't Helike, but it was a huge clue.
We found a substantial Roman building, probably a public building, or, or, or a villa of some kind, something very big.
Ancient writings refer to a Roman town built near where the lost city had been.
It meant they had to be on the right track and when they dug down further they found a few small pieces of classical Greek pottery.
The first classical pot shards were found by one of my assistants.
The first time she brought to me the three or four pot shards she found there together and saw that they were black glaze.
I couldn't believe in my eyes that I had some classical pottery in my hands.
They'd found fragments of pottery with a very distinctive black glaze.
This glaze is typical of the time when Helike disappeared.
For Dora and Steven it meant only one thing that classical Helike must lie deep down, somewhere near the Roman building.
They now thought they were closer to finding the elusive lost city than anyone had ever been.
It just seemed a matter of time, so they brought in a mechanical digger to sink trial trenches all around the area of the Roman building and in one of the first trenches, just three metres below the surface, they seemed to find what they were looking for.
So we have the whole of the north and south And hopefully there is more where this fallen material from the two holes was.
They had uncovered the tops of ancient walls and hidden amongst them they saw what looked like more classical Greek pottery.
They had found a lot of pottery but at first it was very difficult to date this pottery.
The first suggestion was that this might be black glazed classical pottery.
But there was no shiny black surface.
One theory was that it had been burnt off by fires caused by the earthquake, but to find out if this really was the lost city they needed one more bit of evidence proof that the building had once been submerged by seawater and so they sent samples of mud from the trench to a man with a very strange profession indeed.
Carlos Alvarez Zarikian is an expert in microscopic water animals found in soil.
He studies ostracods.
An ostracod is a little tiny shrimp that lives in a shell that looks like a peanut with two valves and they only grow up to two millimetres like from one to two millimetres at the most and they swim, they dig into the sediments, they crawl on the algae and you can find them everywhere.
You can find them in, in freshwater, in the lakes as you can find them in the sea.
Ostracods vary in shape depending on whether they are from freshwater or seawater.
Alvarez Zarikian is one of the few people in the world that specialises in telling them apart.
Freshwater ostracods are very smooth and thin shelled as is the case in, in this example from a freshwater ostracod.
You can see how smooth the shell is which actually many times is used in the identification.
In this other case we have a marine ostracod and you can see how the ornamentation is different.
The ornamentation is much, much heavier than in the other case, in the freshwater ostracod.
You have a much thicker shell and you have many other, other features that is very unlikely you will see in a freshwater type.
If he could find marine ostracods in the soil then this could be evidence that the site was Helike.
Mounted on a special plate he placed a tiny crustacean on the electron microscope and began his analysis.
The pattern of the shell showed the creature had definitely come from the sea.
Not only that, but amongst the sediment he found sea urchin spines, fish scales and other marine creatures called forams.
This ostracod, along with all of the other fossils that we found in this sediment layer are very important because they tell us is the only piece of information up to then that these ancient buildings were actually covered by the sea.
I was delighted of course.
This was, this was to me the first really strong evidence that everything had come together, that this was a classical dated material buried in the sea.
it must be Helike.
What else could it be? Dora and Steven had done it.
The papers said it all.
they had found Helike, so in 2001 they dug down again at the same site and uncovered walls from three more buildings and a lot more pottery and that's when the trouble started because when they put the fragments together there was a shock.
It was something about the shape.
The pottery couldn't be from any time around the classical period.
It was typical of the early Bronze Age, over two thousand years before Helike.
Dora and Steven had got it wrong.
They hadn't found Helike, but a prehistoric settlement.
Normally it would have been an extraordinary discovery, but for them it meant that yet again Helike had eluded them.
To find it they would have to look somewhere else.
In another trench 40m away they had found more Roman remains.
To see if Helike lay beneath them they drilled a small borehole looking for signs of classical remains and this time there was no doubt.
It was another tiny piece of pottery with a distinctive black glaze.
That was two metres below the road, yes, about.
About, two metres.
There's probably a lot of this also because the chance of finding… It could only have come from the time of Helike.
Yes, it is very small.
Look at that.
And so they dug a further exploratory trench nearby, digging deep down through the mud and water to see what lay below and three metres down they found a wall, perhaps part of a house.
So we have a main wall here.
The direction is north-south, that is north is the sea, 55cm wide.
We have a second wall there, 45cm.
And then they uncovered two examples of what they had always hoped to find everyday artefacts from classical Greece.
One was this tiny clay head, a small domestic idol, perhaps used as an offering to the gods, but even better was something they found hidden inside the building they were excavating - a beautiful silver coin and it was dated from just before the disaster.
I've seen many classical coins.
This is superb.
This one is just, is the finest quality that exists really.
The artistry is of the highest order.
It's a beautiful head of Apollo on one side, the flying dove on the other.
It's a small, delicate thing and it's in absolutely mint condition as if someone had just handled it after it came out of the mint and there it was in the ground for 24 centuries when we found it.
But these two objects on their own were not proof.
Dora and Steven had got it wrong once before and they needed more evidence.
To be absolutely sure this was Helike they needed evidence it had been submerged by seawater and hidden in the mud were tiny ostracods, exactly the sort that live in lagoons It meant that this area had once been submerged by a saltwater lagoon 2,500 years ago and finally, in the walls below them, was possible evidence of the disaster itself.
There were signs some huge force had struck the building.
This wall has been knocked down towards the sea.
That is the kind of pattern that you see where you have the, the backwash from the, from the enormous wave going back to the sea knocking down walls that are, that are perpendicular to the flow and knocking them down in the direction of the sea, so we could be standing in Ancient Helike right now.
So it seems that after 15 long years of searching Dora, Steven and their team may have succeeded where so many other archaeologists have failed.
They believe these walls are just the first glimpses of the buildings that must lie on the ground around them.
If Dora and Steven are right, beyond them, towards the hills, should lie the rest of the city waiting to be uncovered.
There are many years of work ahead, but now it seems the city whose destruction inspired the legend of Atlantis may finally have been found.