By Sue Branford
BBC News, Benin
Few tourists reach Benin yet this West African nation has a remarkable story to tell about one of the most shameful episodes in history.
A massive, arched gateway, some 50 feet high, stands alone on the edge of one of the loveliest beaches in West Africa.
A monument in Benin depicts slaves being led away in chains
It is a striking - and in many ways a beautiful - structure, facing out across the Atlantic Ocean towards South America.
Yet it is also bleak beyond words.
Etched across the top of the arch are two long lines of naked, chained men disappearing into the sea.
Called the Gateway of No Return, it is a monument to the hundreds of thousands of Africans who were forced into slave boats on this beach, never to return.
I arrived at this gateway with a group of local historians. By the time I got there, I was choking back tears.
Once the very mention of Ouidah invoked fear among the local population
Not surprising really, as the monument comes at the end of a harrowing two-mile (3.2 km) trek from Ouidah.
Today Ouidah is an attractive town, the spiritual capital of Benin, with a thriving culture centred on the voodoo religion.
But once the very mention of Ouidah invoked fear among the local population.
Tree of Forgetfulness
The Portuguese, the Dutch, the British and the French all had forts near this town, built to defend their trading interests.
And for more than 200 years, the main commodity they traded was people.
Slave traders rounded up men, women and children, at times trapping them with nets.
Their catchment area stretched deep into Africa, even as far as Ethiopia and Sudan.
Once caught the slaves were forced to walk in chains, hundreds of miles to Ouidah.
Once there, they were subjected to a brutal process of brainwashing.
Taken down the slave route that I followed, they were made to walk around a supposedly magical tree called the Tree of Forgetfulness.
They were made to walk around a supposedly magical tree, called the Tree of Forgetfulness
Men had to go round it nine times, women and children seven.
This experience, they were told, would make them forget everything - their names, their family, and the life they had once had.
As if this was not enough, the slaves were then locked into a dark room, built to resemble the hulk of a ship.
In the local language this room was called Zomai, meaning literally: "There, where the light is not allowed."
Its foundations are still visible and the place still seems to exude evil spirits and terror.
After several weeks - or even months - in this hell hole, the slaves were packed in ships for the long crossing to the Americas.
One of the historians told me that most of the slaves went to Brazil, at the time still ruled by Portugal and that some Brazilians played an important role in the trade.
The most infamous was Don Francisco de Souza, an extraordinary wheeler-dealer who, arriving penniless from Brazil, made a fortune out of slave-trading while living in Benin.
He was a colourful figure, allegedly having 99 wives and hundreds of children.
He inspired one of Bruce Chatwin's most famous novels, The Viceroy of Ouidah.
In all, Brazil received some four million slaves from Africa - though not all, of course, from Ouidah.
This was many more than were sent to the United States.
Economically, the slaves did not prosper, for blacks remain by far the poorest ethnic group in Brazil.
Carnival and samba were created by the descendants of former slaves
But culturally their impact was huge.
I lived in Brazil for many years and almost everything that makes Brazil that vibrant, warm country that so many of us love seems to be linked to Africa.
Carnival, samba, Candomble, capoeira - all were created by the descendants of former slaves.
I have always known this, but it was not until my recent trip to Benin that I became aware of just how tenaciously the slaves must have clung to their culture.
Huge efforts were made to cut them off from their past but they failed.
The "tree of forgetfulness" did not work.
Today there is a new twist to the tale.
As yet, Ouidah is unspoilt. Few tourists reach this relatively remote area of West Africa.
Benin's historical sites may soon begin attracting more tourists
But tour operators have spotted the strong combination of wonderful beaches, hot climate, historical sites and, for Europeans, no jet lag.
Moreover, Benin is a relatively safe country with low levels of violence. The people are friendly.
Tourism is just the kind of industry that President Yayi Boni, who came to office earlier this year, is keen to promote.
He was a development banker before entering politics and wants to modernise the country.
Ouidah has a remarkable story to tell and local people need jobs.
But let us hope that Benin does not repeat the mistakes of other developing countries.
Too often tourism has had harmful effects.
Local communities have been evicted from their land. Water resources have been squandered on golf courses.
The local culture has been turned into a vulgar tourist attraction.
It would be ironic indeed if Benin's extraordinary heritage was to open the way for another cycle of exploitation by outsiders.
From Our Own Correspondent was broadcast on Thursday, 7 September, 2006 at 1100 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times