by Graham Hancock

from Hancock's "Underworld" book

“The question was, or is still, is it and, if yes, to what extent is it made by man or overworked by man?

This is the question.”




Dr Wolf Wichmann, geologist, Yonaguni, March 2001
I was in Tokyo in 1996 when the photojournalist Ken Shindo showed me the first images I had ever seen of an awe-inspiring terraced structure, apparently a man-made monument of some kind, lying at depths of up to 30 meters off the Japanese island of Yonaguni at the remote south-west end of the Ryukyu archipelago.

This was the moment, if there ever was just one moment, when the “Underworld” quest began for me and when much that I had learnt in previous years in many different countries began to swing sharply into focus and make sense. I felt an immediate compulsion to explore the beautiful and mysterious structure that beckoned so alluringly from the photographs. And I realized that it would rewrite prehistory if it could indeed be proved to be man-made.

I described in Chapter One how Santha and I learned to dive, and the remarkable synchronicities and good fortune that brought us to Yonaguni in March 1997 to begin a systematic programme of underwater photography and research there that was to continue until mid-2001. I also described some of the other rock-hewn underwater structures that we dived at with our Japanese colleagues at other locations in the Ryukyus – notably at Kerama, Aguni and Chatan at the northern end of the archipelago.

The most complex and intractable problem shared by all of these otherwise very different structures is also the simplest and most obvious question that anyone might wish to ask about them: were they shaped and carved by human hands or could they have ended up looking the way they do as a result of natural weathering and the erosive weapons of the sea?

Though they have an important role to play, geologists are not the only people qualified to decide the answer to such a question. Likewise, though they too are indispensable, archaeologists cannot be the final arbiters. On the contrary, if ever a multi-disciplinary approach was called for then it is here!

For as I’ve tried to show in the previous chapters Japan confronts us with a prehistoric cultural and mythological context into which the rock-hewn structures fit snugly like the missing pieces of a jigsaw puzzle. This context includes a clear tradition of unknown antiquity - still manifest in the present day - in which huge rocks are carved and rearranged amidst sacred natural landscapes. Since this is precisely the puzzling and ambiguous aspect - part natural and part man-made - of the underwater structures scattered around the Ryukyu archipelago, it is foolish and irresponsible to ignore the possibility of a connection.

Yet it is equally foolish and irresponsible to ignore what geology and archaeology have to say on the matter. So it is time, I think, to provide a thorough reckoning.

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The Three Geologists
Three qualified geologists -- Masaaki Kimura , Robert Schoch and Wolf Wichmann -- have dived at Yonaguni, acquired first-hand experience of the underwater structures, and commented publicly on what they saw. So far as I know, they are, at time of writing, the only geologists ever to have dived there. Therefore when we speak of ‘geological opinion’ concerning the Yonaguni anomalies it is important to be clear that we are referring to the work and ideas of just three men who, moreover, do not agree with one another – so there is no concensus. Other geologists who have expressed views without diving at Yonaguni hardly qualify to participate in the debate.

Since there are grave issues at stake concerning our understanding of prehistory and the story of human civilization I propose to devote the necessary space in this chapter to an accurate summary of the views of the three main geological protagonists.

Dr. Kimura
The doyen of the group, and in my view the hero of the Yonaguni saga for his determination, persistence and refreshingly open-minded intellectual approach, is Dr Masaaki Kimura, Professor of Marine Geology at the University of the Ryukyus in Okinawa. He and his students have completed hundreds of dives around the main “terrace” monument at Yonaguni as part of a long-term project in which they have thoroughly measured and mapped it, produced a three-dimensional model, taken samples of ancient algae encrusted on its walls for carbon-dating, and sampled the stone of the structure itself. Professor Kimura’s unequivocal conclusion, based on the scientific evidence, is that the monument is man-made and that it was hewn out of the bedrock when it still stood above sea-level -- perhaps as much as 10,000 years ago. The principal arguments that he puts forward in favor of human intervention are on the record and include the following:

1.  “Traces of marks that show that human beings worked the stone. There are holes made by wedge-like tools called kusabi in many locations.”

2.  “Around the outside of the loop road [a stone-paved pathway connecting principal areas of the main monument] there is a row of neatly-stacked rocks as a stone wall, each rock about twice the size of a person, in a straight line.”

3.  “There are traces carved along the roadway that humans conducted some form of repairs.”

4.  “The structure is continuous from under the water to land, and evidence of the use of fire is present.”

5.  “Stone tools are among the artifacts found underwater and on land.”

6.  “Stone tablets with carving that appears to be letters or symbols, such as what we know as the plus mark ‘+’ and a ‘V’ shape were retrieved from under water.”

7.  “From the waters nearby, stone tools have been retrieved. Two are for known purposes that we can recognize, the majority are not.”

8.  “At the bottom of the sea, a relief carving of an animal figure was discovered on a huge stone.” (1)

9.  On the higher surfaces of the structure there are several areas which slope quite steeply down towards the south. Kimura points out that deep symmetrical trenches appear on the northern elevations of these areas which could not have been formed by any known natural process.

10.  A series of steps rises at regular intervals up the south face of the monument from the pathway at its base, 27 meters underwater, towards its summit less than 6 meters below the waves. A similar stairway is found on the monument’s northern face.

11.  Blocks that must necessarily have been removed (whether by natural or by human agency) in order to form the monument’s impressive terraces are not found lying in the places where they would have fallen if only gravity and natural forces were operating; instead they seem to have been artificially cleared away to one side and in some cases are absent from the site entirely.

12.  The effects of this unnatural and selective clean-up operation are particularly evident on the rock-cut ‘pathway’ [Kimura calls it the ‘loop road’] that winds around the western and southern faces of the base of the monument. It passes directly beneath the main terraces yet is completely clear of the mass of rubble that would have had to be removed (whether by natural or by human agency) in order for the terraces to form at all.(2)

Dr. Schoch

The second geologist to dive at Yonaguni, Professor Robert Schoch of Boston University, has vacillated tenaciously in his opinions – but I take this as a sign of an open-minded scholar ever willing to revise his views in the light of new evidence.

Thus when we first dived there together in September 1997, he was sure that the structure was man-made.(3) Within a few days, however, he had changed his mind completely:

“I believe that the structure can be explained as the result of natural processes The geology of the fine mudstones and sandstones of the Yonaguni area, combined with wave and current actions and the lower sea-levels of the area during earlier millennia, were responsible for the formation of the Yonaguni Monument about 9000 to 10,000 years ago.”(4)

A few days later, Schoch softened his position again:

“After meeting with Professor Kimura, I cannot totally discount the possibility that the Yonaguni Monument was at least partially worked and modified by the hands of humans. Professor Kimura pointed out several key features that I did not see on my first brief trip. If I should have the opportunity to revisit the Yonaguni monument, these are key areas that I would wish to explore.”(5)

Schoch did have an opportunity to revisit the structure in the summer of 1998, carrying out several more dives there. Then in 1999 in an interview given to the BBC science programme “Horizon” for a documentary attacking my work – and in the same year in his own book “Voices of the Rocks” -- he expressed what sound like two very different, even contradictory opinions about the structure.

Here is the relevant section from the BBC Horizon transcript:

NARRATOR: “Yonaguni looked as if it could be a spectacular discovery and Hancock needed corroboration. He invited the Boston University geologist Robert Schoch to inspect the site. Professor Schoch has taken a keen interest in unorthodox views of the past and he welcomed the chance to examine the underwater discovery. Schoch dived with Hancock several times at Yonaguni.”

PROF. ROBERT SCHOCH (Boston University): “I went there in this case actually hoping that it was a totally man-made structure that was now submerged underwater, that dated maybe back to 6,000 BC or more. When I got there and I got to dive on the structure I have to admit I was very, very disappointed because I was basically convinced after a few dives that this was primarily, possibly totally, a natural structure Isolated portions of it look like they're man-made, but when you look at it in context you look at the shore features etc and you see how, in this case, fine sandstones split along horizontal bedding plains that gives you these regular features. I'm convinced it's a natural structure.”(6)

Well that seems straightforward. But then here is what Schoch says in “Voices of the Rocks”:

“Possibly the choice between natural and human-made isn’t simply either/or. Yonaguni Island contains a number of old tombs whose exact age is uncertain, but that are clearly very old. Curiously the architecture of the tombs is much like that of the monument. It is possible that humans were imitating the monument in designing the tombs, and it is equally possible that the monument was itself somehow modified by human hands. That is, the ancient inhabitants of the island may have partially reshaped or enhanced a natural structure to give it the form they wished, either as a structure on its own or as the foundation of a timber, mud or stone building that has since been destroyed. It is also possible that the monument served as a quarry from which blocks were cut, following the natural bedding, joint and fracture planes of the rock, then removed to construct buildings that are now long gone.


Since it is located along the coast the Yonaguni Monument may even have served as some kind of natural boat dock for an early seafaring people. As Dr Kimura showed me, ancient stone tools beautifully crafted from igneous rock have been found on Yonaguni. Significantly, Yonaguni has no naturally exposed igneous rocks, so the tools, or at least the raw materials from which they were made, must have been imported from neighboring islands where such rock is found. The tools could have been used to modify or reshape the natural stone structures now found underwater off the coast of Yonaguni. The concept of a human-enhanced natural structure fits well with East Asian aesthetics, such as the feng shui of China and the Zen-inspired rock gardens of Japan. A complex interaction between natural and human-made forms that influenced human art and architecture 8000 years ago is highly possible."(7)

As further evidence for a very ancient human role in the construction of the Yonaguni monument, Schoch then sets out an argument of mine, advanced in my 1998 book “Heaven’s Mirror”, that the structure is not only man-made but could also have served a specific astronomical function -- since calculations show that around 10,000 years ago, when it was above water, it would have stood on the ancient Tropic of Cancer.(8) Writes Schoch:

“The ancients, I suspect, knew where the tropic was, and they knew that its position moved slowly. Since Yonaguni is close to the most northerly position the tropic reaches in its lengthy cycle, the island may have been the site of an astronomically aligned shrine.”(9)

In summary, therefore, Schoch has not come down definitively either on one side of the fence or on the other but seems to be wavering in the direction of a compromise in which the structure is both natural and man-made at the same time.

I cannot avoid adding that all rock-hewn structures, whether the weird terraced granite outcrop at Qenko near Sacsayhuaman in Peru,(10) or the wonders of Petra in Jordan, or the temples of Mahabalipuram in South India are, by definition partly natural – the base rock out of which they are hewn – and partly man-made. They can’t help but be anything else.

Dr. Wichmann
The third geologist, German science writer Dr Wolf Wichmann, has definite opinions and expresses them with certainty. In 1999 he informed Der Spiegel magazine – who had taken him to Yonaguni -- that he regards the underwater monument as entirely natural. He made just three dives on the main terraces and then declared:

“I didn't find anything that was man-made."(11)

Japan's marine scientists “haven't got a clue” what the terraced underwater structure at Yonaguni is, reports Der Spiegel:

‘"It is unlikely to be anything natural" said the oceanographer Terukai Ishii from Tokyo. Masaaki Kimura, a marine researcher at the Rykyus University (Okinawa) talks about "a masterpiece". He thinks the structure is a sacred edifice built by a hitherto unknown culture possessing advanced technical abilities.

‘The debate going on in the Orient has awakened the curiosity of the West. People with second sight find themselves magically attracted by "Iseki Point ("ruins"). At the beginning of 1998 the geologist Robert Schoch, who believes the Sphinx was built by the people of Atlantis [sic -- completely untrue; Schoch does not believe any such thing] swam down to the site and declared it to be "most interesting". The guru of ancient antiquity and best-selling author Graham Hancock was also investigating the site. After an excursion in a submersible he records that at the base of the monument can be seen a "clearly-defined path." [actually I have never been in a submersible at Yonaguni and I do not consider my four years of hands-on diving there as any kind of excursion; there is, however, a clearly-defined path at the base of the monument].

‘The rock expert Wolf Wichmann could not corroborate these conclusions. In the company of a team from SPIEGEL TV he returned to explore the coastal area, under threat from tsunamis. In a total of three diving operations he gathered rock samples and measured the steps and "walls". He was unconvinced by his findings: "I didn't find anything that was man-made".

‘During the inspection it was revealed that the "gigantic temple" is nothing but naturally produced bedded rock. The sandstone is traversed by vertical cracks and horizontal crevices. Perpendicularity and steps have gradually developed in the fracture zones. The plateau at the top are referred to by Wichmann as typical "eroded plains". Such flat areas occur when bedded rock is located right in the path of the wash of the waves.

‘Suggestive pictures rich in detail and contrast may indeed reveal something else, but in general the mass of rock looks like a structure rising out of a sandy bed, with no sign of architectural design. The plateau have gradient sections, and there is no perpendicular wall. Some of the steps just end nowhere; others are in a spiral, like steep hen-roosts.

‘The stony blocks show no signs of mechanical working. "Had the 'ashlars' been hewn by tools, they would have been studded with flutes and cuts and scratches", said Wichmann. Three circular recesses on the topmost plateau, referred to by Kimura as column foundations, are nothing but "potholes". These occur when water washes through narrow spaces.

‘Facts like these fail to stem the current epidemic of mystery-fever. The Yonaguni monument has for some time played a key role in the world picture of archaeological dreamers.(12)

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The One Archaeologist
One archaeologist has dived at Yonaguni and studied its underwater structures first hand. Others in his profession who have commented have done so from their desks after browsing through photographs or looking at videotape of the structures. As is the case with the armchair geologists, their opinions can only be of limited value until they have dived there themselves.

By contrast the opinion of the only experienced marine archaeologist in the world who has ever dived at Yonaguni must count for a great deal more.

That archaeologist -- whose official report is reproduced in part below -- is Sundaresh from the National Institute of Oceanography in Goa, India. The reader will recall that we dived with him and other NIO archaeologists at Dwarka in March 2000 and again at Pumpuhar in February 2001. Between these expeditions in India, Sundaresh participated with us in an expedition to Yonaguni in September 2000 that had been sponsored once again (as had Robert Schoch’s visit in September 1997) by Seamen’s Club.

Also participating in the September 2000 expedition was Kimiya Homma, a businessman from Hokkaido, whose firm owns two very useful high-tech ROVs (remotely operated vehicles) for unmanned exploration in water too deep to be readily reached by divers. So that an effective search for further structures around Yonaguni could be mounted in the short time available, Homma had brought one of the ROVs with him and also an expert team of support staff and technical divers.

Because it is a unique document of reference, being – so far – the first and only evaluation of a wide range of Yonaguni’s underwater structures by a marine archaeologist, I reproduce below several sections from Sundaresh’s expedition report. Some of the specific submerged sites that we visited with Sundaresh during the expedition are not yet familiar to the reader from the brief account given in Chapters 1 and 25 but will be described shortly:

1-12 September 2000

is the most south western island of Japan and closest to Taiwan (about 69 nautical miles). This island is almond shaped with 10 km length from (east to west) and 4 km width (north to south). An international expedition was organized by the Seamen's Club, Ishigaki Japan to further explore the underwater structures in the area. This report describes the archaeological significance of the structures found during the expedition.

Underwater massive structures were found initially by Mr. Aratake a local resident of Yonaguni island during 1986-87. He named this point as Iseki (“Monument”) Point. He was looking for hammerhead sharks schooling around the island, when a massive man-made underwater structure was noticed at a depth of 30 m. This was his first discovery. Later more monuments were found by Aratake and other divers in nearby Tatigami and “Palaceareas.


4.1 Offshore Explorations

Two boats were chartered for explorations off Yonaguni waters from 2 September 2000 to 8 September 2000. The Remotely Operated Vehicle (ROV) was deployed simultaneously with side scan sonar and echosounder. The ROV was operated with generator power supply. The system was operated in waters between 40 to 80 meters depth around Yonaguni. The survey revealed rock cut channel about 1 m wide and more than 20 m long at 2 sea mounts. The ROV observations were confirmed by diving.


5.1 Terraced Structure and Canal

A large terraced structure of about 250 meters long and 25 meters height was studied south of the Arakawabana headland. Known locally as Iseki Point, the terraced structure is bound to the northern side of an elongated, approximately east-west trending structure, designated by Professor Masaaki Kimura, University of the Ryukyus, as an approach road. But our observation of the proposed road-like structure suggests that it is more likely to be a canal. The overall width of the terraced structure is around 100m. From each of the terraces; a staircase leads downwards to the canal (road ?).

The length of the canal appears to be more than 250 m, while the canal has a width of 25 m. The purpose or utility of this canal structure is intriguing. Our observation all along the canal indicates that, the western end of the structure begins underwater opening away from the terraced structure into the open sea. The width, height and terraced northern side of the canal force us to suggest that the canal structure might have served as a channel for small boats communicating with the Arakawabana headland. The southern natural outcrop wall probably had provided a buffer wall for strong open sea waves. This interpretation appears quite reasonable because the height of the southern wall of natural outcrop and the northern terraced wall are nearly same. The terraces and attached staircases might have been used for handling, loading and unloading boats sailing through the channel. Thus it appears in all probability that the terraced structure and canal might have served as a jetty before submergence to present depth.

5.2 Monolith Human Head

A large monolith that looks like a human head with two eyes and a mouth was studied at Tatigami Iwa Point. A human-cut large platform in the same monolith extends outwards at the base of the head. An approach way leads to this platform from the shore-side.

The surrounding basal platform is quite large (about 2500m2 ), and could easily have accommodated more than two thousand persons sitting. The human head and associated platform with an approach road are suggestive of an area of worship or community gatherings.

5.3 Underwater Cave Area

Diving operations revealed caves at 8 to 10 m water depth at “Palacearea. The entry to these caves was possible only through the large 1 meter radius holes on the cave roof. Inside the cave a boulder about 1 meter diameter engraved with carvings was observed. About 100 m towards the eastern side of the caves more rock engravings were noticed on the bedrock. These rock engravings are believed to be man-made.

Once upon a time these caves were probably on the land and were later submerged. The rock engravings inside the cave and on the bedrock were probably carved out by means of a tool of some sort. However, it is very difficult to say that these are rock art of this or that period, or a script.

5.4 Megaliths Point

Diving operations revealed two big rectangular blocks measuring 6 meters in height, about 2.5 meters in width (both) and 4.9 meters thickness which have been located towards the western side of Iseki point... These rectangular blocks are designated by Japanese workers as megaliths. These blocks have been located in between two natural rock outcrops. The approach way to these megaliths is through a tunnel measuring about 3 m long, 1 m high and 1 m width.

The shape, size and positioning of these megaliths suggest that they are man-made. It is believed that the people of Japan’s extremely ancient Jomon culture used to worship stones, rocks, (Hancock, personal communication, 2000). In light of this practice, it may be worthwhile to suggest that, these megaliths might have been used as objects of worship. However a thorough investigation in this regard is necessary before assigning a definite purpose to these megaliths.

The terraced structures with a canal are undoubtedly man-made, built by cutting an existing huge monolithic outcrop. The rectangular terraced structure and canal probably might have served as a jetty for handling, loading/unloading small boats before its submergence to present depth.


The monolith rock-cut human head and associated platform might have served as an area of worshiping or community gatherings.

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The Score So Far
By my count so far I have one marine archaeologist, Sundaresh, who is convinced that the Yonaguni structures are “undoubtedly man-made”, and who represents 100 per cent of all the archaeologists who have ever dived there up to time of writing. I also have one marine geologist, Masaaki Kimura, who believes the same thing, a second, Robert Schoch, who is undecided, and a third, Wolf Wichmann who is convinced that they are natural.

I decided when I got the opportunity that I should try to dive at Yonaguni with Wichmann and see if I could change his mind. To this end, a few months after the Der Spiegel article appeared, I made the following statement on my website:

“I would like to offer a challenge to Wolf Wichmann. Let us agree a mutually convenient time to do, say, 20 dives together at Yonaguni over a period of about a week. I will show you the structures as I have come to know them, and give you every reason why I think that the monuments must have been worked on by human beings. You will do your best to persuade me otherwise. At the end of the week let's see if either side has had a change of mind.”(13)


In March 2001, on a mini-expedition funded by Channel 4 Television, Wichmann took up my challenge. A small, wiry, dark-haired, unpretentious man, I liked him the moment I met him, and continued to do so throughout the week that we spent diving in Japan and arguing, in a mood of amiable disagreement, about what we were seeing underwater.

Predictably we did not reach a consensus: Wolf left Yonaguni still holding most of the opinions with which he had arrived, and so did I. But I think that we each gave the other some worthy points to ponder. I know that I benefited from what amounted to a very useful field seminar on the natural history of submerged rock and began to understand clearly for the first time exactly how and why a geologist might conclude that the Yonaguni underwater structures are entirely natural - or at any rate (to sum up Wolf’s position more accurately) that they all could have been formed by known natural forces with no necessity for human intervention.

Before going on to Yonaguni, Wolf and I paid a visit to Professor Masaaki Kimura at his office in the University of the Ryukyus. I started the ball rolling with a general question for Professor Kimura concerning the age of the structure:

GH: People can argue for the next five centuries about whether what we see underwater at Yonaguni is manmade or artificial. But one thing which we can hopefully get clear is how old it is when it was submerged?

So the first question I want to ask you is what is your view of the age of this structure? The last time that it was above water?

PROF KIMURA: This construction has been submerged since 6000 years ago, because the coralline algae attaching to the wall of this structure shows 6000 years.

GH: And those coralline algae, because they're organic, you've been able to carbon date them?

PROF KIMURA: Yes, Carbon-14.

GH: Right. So that tells us the age of that biological item it's 6000 years old and it's attached to a stone structure which, therefore, must be older than that.

PROF KIMURA: It must be older, and so in general 6000 years ago the sea level at that time [was lower] So if this was made by men, this must be when this area was land it's about 9000 or 10,000 years ago.

GH: 9000 or 10,000 years ago? So -- again to clarify, because I need to get this straight, -- you're saying that 9000 or 10,000 years ago, the whole area was above water and the date of submergence would be about 6000 years ago?

PROF KIMURA: Before 6000 years ago.

GH: This is the problem with Carbon 14 isn’t it? It dates the organism, not the structure. So then you can only say that the structure is older than that, but how much older is not sure. How much work have you done on sea level change as a dating guide? And how big a factor is the possibility of sudden maybe recent land subsidence as a result of earthquake?

PROF KIMURA: Yes, I'm looking for such evidence, that is geological evidence, but there is no evidence of movement. If this area had subsided by movement it would be due to earthquakes and faulting, but there is no active fault nearby, the fringing coast is continuous, and between the beach and Iseki Point, there is no discontinuity or fault.

WOLF: I see.

GH: That makes things fairly clear then. It leaves us with the sea level issue on its own to base a date on, without complicating factors, which is great. At least we can be clear on one thing.

WOLF: I think that questions for sea level rise are very fairly proved by scientific evidence here in the area. I mean, they're experts in their field.

GH: So you'd have no problem with the 9000 year date?

WOLF: No, no not at all. No, the question was, or is still, is it and, if yes, to what extent is it made by man or overworked by man? This is the question.

GH: Well hopefully we'll get a chance to investigate that when we go to Yonaguni.

PROF KIMURA: We need to research much more.

WOLF: Yes.

GH [speaking to Prof Kimura]: I mean you're practically the only person who's done - you and your team here - have done continuous research for some years. But almost nobody else is working on it, I think, at the moment?

PROF KIMURA: Japanese scientists cannot dive.

Throughout our discussion Professor Kimura strongly maintained his commitment to the manmade character of Yonaguni’s underwater monuments - not simply on the basis of his technical findings, cited earlier which I need not repeat here, but also, and I found persuasively, because:

“This kind of topography - if this has been made by nature it is very difficult to explain the shape.”

Wolf’s riposte was immediate:

“So what I would say to that formation is that I’ve seen many natural formations, especially coastlines, being worked out by waves and wind, especially with the help of weapons, erosive weapons -- sand and so on. Seeing with the eye of a geologist or a morphologist it is, OK, a very fine, a very nice thing, but possibly made by nature.”

I asked Wolf whether in fact he had every seen anything like the Yonaguniformation” anywhere else in the world.

“Not in that exact combination,” he replied. “This is what is surprising me; it's a very strong, compressed combination of the different shapes and the different figures you can find naturally in the world somewhere.”

“But you don't usually find them in combination like this?”

“No, I haven't seen that. So that is a marvel. It is a very beautiful formation.”

“Or the work of human beings? I prompted.

“Or of that. So that's what we're here for.”

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