Ghana is a holiday destination but with a difference. Its tragic history is being turned to the country's advantage.

Watch Mark Doyle's report on Ghana's new form of educational tourism

No one knows for certain how many slaves were taken from Ghana, but the dungeons dotted along the coast were used both for prisoners from this country's hinterland, and as transit points for slaves from other African states.

Now African-American tourists are blazing a new trail to Ghana.

One such tourist, Sheila Lane, said after a tour of fort El Mina: "It's just sad to think that the Dutch, and all the other people that they were talking about on the tour were supposed to be God fearing people, but then they didn't see the Africans as being people, having rights and they violated their rights."

El Mina is the oldest European structure in West Africa and was built to protect gold trading routes before the commerce in human beings began.

Its violent History includes control by the Portuguese, Dutch, Spanish and British. The great sea faring powers fought amongst themselves as well as the local gold-rich Ashanti empire.

The refurbishment of Ghana's castles has encouraged a tourist trade, which has now overtaken timber exports as a foreign exchange earner. But the new trade is about much more than just money.

Ghanaian authorities believe we can learn from the grim history of the dungeons

El Mina provokes powerful emotions among its visitors - black and white. The roles some Africans played in capturing slaves and then sold on to European traders is not forgotten, and the tour guides sometimes dread hosting mixed groups of black and white visitors.

Professor Nkunu Akyea of the Ghana Tour Guides Association said: "I had a group, and it almost broke into a fight between the black and the white. The same group had travelled together from wherever and come here, each one, pointing a finger at the other."

Outside the castle walls El Mina is a fishing port. Many of the people here are too busy making a living to spend time visiting their castle.

Outside the castle walls El Mina is a fishing port

But the tourist industry is likely to play an increasingly important role in Ghana. Here fish stocks are being depleted by foreign factory ships that ply the high seas. El Mina's fishermen have to travel further and further to make a decent catch.

Fishing for tourists could in the long run prove an easier way to make a living.