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SOMETIMES the biggest things can be the hardest to find. How else do you
explain the failure of generations of Nigerian and European archaeologists to
spot Sungbo鈥檚 Eredo, the ramparts of a thousand-year-old kingdom not an hour鈥檚
drive from Lagos. They are very big: the earth wall and ditch are 160 kilometres
long and in places tower seven storeys high, complete with guardhouses, moats
and garrison barracks. They enclose an area the size of Greater London, or 30
times bigger than Manhattan. But it took a British geographer from the
University of Bournemouth to recognise their significance.

Patrick Darling stumbled upon Sungbo鈥檚 Eredo five years ago, when he stopped
his car along the Pan African Highway in southern Nigeria and set off on foot
into the undergrowth. What he found that day was the jewel in the African civil
engineering crown. Eredo is the most outstanding example of thousands of ancient
city ramparts and boundary embankments and ditches that Darling believes stretch
across Nigeria and much of West Africa.

Darling says that tropical landscapes are littered with ancient earthworks
that dwarf more famous ancient mega-structures such as the ruins of Great
Zimbabwe in southern Africa or the pyramids of Egypt and even compare with the
Great Wall of China. He has made it his life鈥檚 work to unlock the secrets of
these Cinderellas of the archaeological world.

Darling did not, strictly speaking, discover Sungbo鈥檚 Eredo. Local African
villagers and pilgrims knew about it all along. Eredo means a ditch, and they
believe that the earthworks were built for Bilikisu Sungbo, a fabulously wealthy
but childless widow who wanted a monument to her rule of the area. Thousands of
Islamic pilgrims come each year to pay homage to Sungbo at her shrine, which
lies just inside the ramparts.

Sungbo is a Yoruba name. The Yoruba came from the savannah lands of
modern-day central Nigeria more than 6000 years ago and still live in the region
today. But local legend has it that Sungbo was in fact the Queen of Sheba, who
appears in both the Bible and the Koran as the wife of Solomon and the ruler of
a wealthy kingdom in Arabia or Ethiopia. The link with the Queen of Sheba
originates in the late 19th century according to Peter Lloyd, a retired British
anthropologist, who came across Sungbo鈥檚 Eredo forty years ago, though he did
not realise its significance.

鈥淭he educated Nigerians who first wrote up the local oral histories linked
everything to Biblical stories or the Koran when they could,鈥� he says. 鈥淎nd the
idea of a black African queen led them straight to Sheba.鈥� Darling agrees with
Lloyd that anything more literal stretches credulity. Sheba was supposed to be
around 3000 years ago, he says, so there鈥檚 a 2000-year discrepancy in dates.

The reality may not be so romantic, but it is still impressive. 鈥淪ungbo鈥檚
Eredo is Africa鈥檚 largest single ancient monument,鈥� says Darling. The ramparts
encircle an area 40 by 35 kilometres, with sheer walls rising to 10 metres in
places. Darling has also unearthed the charcoal remains of fires set to clear
the bush before the walls were built. Radiocarbon dating reveals that the
charcoal is around 1200 years old, give or take a century or so.

鈥淭his pushes back the date of any known African rainforest kingdom by 400
years,鈥� he says. 鈥淚t is the first definitive proof that there was substantial
state formation in the African rainforest at roughly the same time as in the
蝉补惫补苍苍补丑.鈥�

So who masterminded the construction of Sungbo鈥檚 Eredo? Tracking events more
than a millennium ago in a country with no written tradition is not easy. The
ramparts seem to mark the boundary of an ancient kingdom, probably populated by
the Ijebu, one of several groups of people collectively called Yoruba.

Sungbo鈥檚 Eredo could have been built by the Awujale dynasty, which still
reigns in the town of Ijebu-Ode in the heart of the Eredo. Its oral history
encompasses 57 kings and queens. Before 1760 the dating is hazy, but Lloyd and
Darling believe the dynasty probably began around AD 1150. So it looks as though
the Eredo was already under construction when the Awujale kings took over. And
that leaves Sungbo. Without any better evidence, Darling is inclined to accept
oral history. So this walled kingdom must have fallen to the Awujale dynasty
some time after the death of the childless matriarch.

It would have taken millions of hours of toil to build Sungbo鈥檚 Eredo. But
Darling is most impressed by the skill displayed in surveying and construction.
The Ijebu had the 鈥渁bility to retain a coherent masterplan in thick rainforest,
frequently interrupted by great fingers of swamp鈥�, he says. 鈥淲ithout compass or
aerial photographs, they were able to keep the ramparts on course whatever the
辞产蝉迟补肠濒别.鈥�

Today, much of the bare earth, dug and heaped by the Ijebu people early in
the ninth century鈥攁round the time that Charlemagne ruled in
Europe鈥攊s covered in green moss. The ditches reek of rotting vegetation
and echo to the sound of croaking frogs. The whole thing is engulfed by trees,
undergrowth and fetid swamp. It lies overgrown and apparently forgotten, rather
like an old railway embankment in the English countryside.

Still, it seems extraordinary that such a large structure could have evaded
the eyes of outsiders. In 1505, the Portuguese explorer Pacheco Pereira reported
the existence of a 鈥渧ery large city called Geebuu, surrounded by a great moat鈥�.
The conventional view is that this was Ijebu-Ode, where the Portuguese traded
slaves for brass bracelets. But Darling says that Ijebu-Ode does not have a
large moat and it could have been a reference to Sungbo鈥檚 Eredo.

Then the written records go silent until Lloyd鈥檚 brief report in a journal of
Yoruba studies called Odu in 1959. 鈥淚 found Sungbo鈥檚 Eredo when
researching customary land laws,鈥� recalls Lloyd. 鈥淲hen I looked at aerial
photographs, it was quite visible, partly because it was still covered in trees,
unlike much of the surrounding land.鈥�

For Darling, Sungbo鈥檚 Eredo is part of a much bigger story that began 30
years ago while he was teaching in Nigeria and coaching a state cycling team.
While out training one day, he spotted vast networks of Nigerian earthworks
around Benin City, which is 250 kilometres east of Lagos and a long way from
Sungbo鈥檚 Eredo. Local officials offered him a scholarship to research them and
since then, whenever local politics and his teaching career have allowed, he has
visited Nigeria to carry on with the survey, using little more than his bicycle
and an orienteering compass.

No single structure in the Benin network is as large as Sungbo鈥檚 Eredo, but
collectively they dwarf it entirely. They extend for some 16 000 kilometres in
all, in a mosaic of more than 500 interconnected settlement boundaries. They
cover 6500 square kilometres and were all dug by the Edo people. In all, they
are four times longer than the Great Wall of China, and consumed a hundred times
more material than the Great Pyramid of Cheops. They took an estimated 150
million hours of digging to construct, and are perhaps the largest single
archaeological phenomenon on the planet. No wonder he has mapped only around a
tenth of them.

His radiocarbon dating suggests that the Benin earthworks were a rolling
programme, most of which was carried out between AD 800 and 1500. At the core of
the complex, the enclosures are small, surrounding individual clan communities.
In these areas there may be 5 kilometres of earthworks in every square
kilometre. But towards the periphery, they are large, with a circumference of up
to 100 kilometres, and a wide no-man鈥檚-land between the enclosures. Darling
believes their development probably marks the gradual migration of farmers as
they extended their domain deeper into the jungle.

With the aid of anthropologists, including Dan Ben-Amos, an African
specialist at Pennsylvania State University, Darling has started to piece
together the social as well as the physical structure of the settlements. The
settlements include places such as Ohovbe, a migration camp 7 kilometres east of
Benin City, the rash of settlements all called Oka that share a common earthwork
boundary, and the city of Udo, which once rivalled Benin and boasts 10
kilometres of ramparts containing half a million cubic metres of earth.

The studies are helping to unearth the earliest history of this area. In
Ishan Forest northwest of the Benin earthworks, for instance, slash-and-burn
farmers first cleared the rainforests at least 2000 years ago. It was here too
that the Edo people dug the earliest banked compounds in the Benin complex,
around AD 500. At about this time they also switched to more settled methods of
farming. Perhaps this gave them more time for digging out the walls of the
settlement. Or maybe both developments arose after they started making iron
implements.

The question remains: why go to all that trouble, whether at Benin or
Sungbo鈥檚 Eredo? The earthworks probably had some role in defence, says Darling.
But a deep, dark rainforest is a very different place from an open plain, where
most of the world鈥檚 defensive ramparts are built. 鈥淚n the rainforest visibility
is only a few metres. Warfare is about poisoned arrows and sneaking about, not
cavalries and pitched battles,鈥� he says.

Equally important, perhaps, the earthworks kept the people of the kingdoms
together and under control. 鈥淎ll over this region, you find that the societies
that had ramparts seem to have been more cohesive and to have survived for
longer against outsiders,鈥� says Darling.

But he believes the ramparts also had an important spiritual role,
especially, perhaps, for people who came from outside the rainforest and who may
well still have been afraid of it. According to tradition, the earthworks
represent the boundary between the real world inside the enclosure and the
spirit world outside. The ditches in particular are a kind of limbo land. 鈥淚n
Britain we have the phrase Devil鈥檚 Dyke, and it鈥檚 rather like that. Evil spirits
live there,鈥� he says.

Two centuries ago, European explorers noticed that communities here cast the
corpses of the poor into the ditches. And according to local tradition the
inhabitants buried charm pots beneath earthworks gateways and applied potions to
the earth walls to ward off evil spirits. To this day, there is an annual
ceremony to appease the spirits of the gateways. And people throw gifts to the
spirits in the ditches as they return home from funerals held outside the
walls.

鈥淒arling鈥檚 is a major piece of work of importance for the whole of Africa,
and it hasn鈥檛 had the attention it deserves,鈥� says John Alexander, an
archaeologist at the University of Cambridge. 鈥淗e has done wonders, but of
course what it needs is much more field work. Unfortunately, nobody else, either
from Nigeria or abroad, is investigating these earthworks.鈥�

So why are others archaeologists staying away in droves? Foreign
archaeologists seemed to prefer the cooler climates of Egypt, Ethiopia and
southern Africa. They also prefer digging to 鈥渢he basic pioneering surveys of
Africa鈥檚 rich archaeological landscapes鈥�, says Darling. 鈥淔or every tonne of
carefully sifted soil in Egypt, less than a teaspoon has been glanced at in West
Africa.鈥� And because none of them have been to the region, they assume there is
nothing to find there.

Even Nigerians have been strangely reluctant to venture into the field. 鈥淚
suppose earthworks weren鈥檛 very exciting,鈥� says Lloyd. 鈥淭here is not much chance
of finding grand tombs of jewellery or anything.鈥� There are three universities
with archaeology departments within an hour of Sungbo鈥檚 Eredo, he says, but in
40 years, nobody has gone to investigate.

Darling is encouraging Nigerian efforts to get the site listed as a UNESCO
World Heritage Site. But meanwhile, parts have been bulldozed by logging
companies and one large section was ripped up to make way for a World Bank
irrigation project which, says Darling, 鈥渉as still to produce a single sack of
谤颈肠别鈥�.

Patrick Darling is helping piece together a radically new history for the
rainforest regions of West Africa. And it chimes in with research going on all
round the tropics. The idea of virgin rainforest, largely untouched by native
people, is giving way to the realisation that humans have sculpted even deep
jungle for perhaps thousands of years. The theory that civilisation only got
going in drier climates鈥攁nd that rainforests dwellers were happy to live a
semi-nomadic life of hunting, gathering and sporadic farming鈥攊s being
knocked into some very long grass.

The Maya civilisation that flourished in the Central American rainforests
between AD 300 and 900 once seemed exceptional. But no longer. During the past
decade Anna Roosevelt of the Chicago Field Museum of Natural History has
unveiled the 鈥渕ound builders鈥� in the Amazon jungle. Sometime between AD 400 and
1400, they constructed hundreds of 20-metre-high earth mounds on the forest
floor that covered up to a square kilometre.

Urban centres then grew up around the mounds. The Amazon civilisation
ultimately subjugated tens of thousands of people and covered 20 000 square
kilometres. The land was criss-crossed by networks of causeways and irrigation
canals that were later copied right across South America.