Now, only a shell remains -- a crumbling monument teetering at the edge of the sea.

For centuries, Ghana's coastline has borne the brunt of history. Today, it is being consumed by nature and neglect as climate change, rising sea levels and unchecked human activity eat away at the 550-kilometre (340-mile) shore.

Villages are vanishing, and with them, centuries-old heritage.

The modern economy is also at risk. A few metres (yards) away from the fort, Ernestina Gavor cleans a glass behind a bar.

"I'm hoping it survives a few more years," she told AFP, noting that the restaurant relies on tourists to keep afloat.

Fort Prinzenstein, once a Danish slave fort and now a UNESCO World Heritage Site, is among the most threatened sites on Ghana's coast.

James Ocloo Akorli, its caretaker for 24 years, has watched the Gulf of Guinea claw away at the structure -- and his memories.

The coast used to be about four miles from the fort, he recounted. The village he was born in has been swept away, his family packing up and leaving in 1984.

Today, only 10 percent of the original fort survives. The dungeons that once held enslaved women are still visible, but the men's quarters have been swallowed by the waves.

"This fort used to be significant," Akorli told AFP. "Now, we are losing everything -- our history, our homes and our livelihoods."

- Modern economy at risk -

Ghana's castles and forts -- particularly Cape Coast Castle and Elmina Castle -- attract thousands of visitors each year, mostly African Americans seeking to reconnect with their ancestral past.

"For Afro-descendants, they are sacred places -- testimonies of our resilience, our pain and our ingenuity. If we lose them, we lose our connection to history," said Edmond Moukala, UNESCO's representative in Ghana.

But preserving that history is proving difficult.

Chris Gordon, an environmental scientist at the University of Ghana, warned that the scale of intervention required was beyond the country's current means.

"You'd need the kind of coastal defences they have in the Netherlands," he told AFP.

History isn't the only thing at risk.

Samuel Yevu, 45, was among those displaced after "tidal waves", as ocean surges are locally known, swept through nearby Fuvemeh village in March.

"We used to have coconut trees, fishing nets, everything. Now it's all gone," said Yevu, whose family sleeps in a school classroom.

In 2000, Ghana launched a $100-million sea wall project to protect communities like Keta, home to Fort Prinzenstein. It saved the town, but shifted erosion eastwards, devastating places like Agavedzi and Aflao.

Experts warn that short-sighted interventions -- like groynes and sea walls -- can worsen erosion by redirecting the ocean's energy elsewhere.

Meanwhile, human interventions that worsen natural coastal erosion continue unabated.

"Sand mining, river damming, unregulated construction -- they all starve the coast of sediment," said Gordon.

A study by the University of Ghana suggests the country could lose key landmarks like Christiansborg Castle and Kwame Nkrumah Mausoleum within decades if nothing is done.

The country's modern economy is also heavily reliant on coastal activities, from ports and fishing to oil and gas.

Yet the destruction of Fort Prinzenstein -- stone of the prince, in the Danish language -- is particularly poignant because of its unique role in the slave trade.

Akorli recounted how enslaved people from modern-day Benin, Nigeria and Togo were branded, sorted and shipped from the fort, even after Britain outlawed the slave trade in 1807.

"This is the only fort in the Volta region. Togo doesn't have one. Benin doesn't. Nigeria doesn't," he said.

- 'Losing a graveyard' -

At Cape Coast Castle, a tour guide warned of a similar fate.

"Every day, people from the diaspora come here and cry in these dungeons," he said, requesting anonymity since he was not authorised to speak to the media. "If this castle disappears, it's like losing a graveyard of millions. It's not just Ghana's history -- it's world history."

Even so, maintenance remains neglected.

Moukala, from UNESCO, believes the core problem is not erosion, but lack of care.

"If there had been regular maintenance, we wouldn't witness the severe deterioration. These were buildings meant to last centuries. But neglect, urban development and vandalism have destroyed many."

In Keta, Akorli's plea to authorities is urgent.

"They must come as a matter of urgency, restore this fort to boost visitation, so that our brothers in the diaspora will not lose their roots."

strs/nro/kjm

HERITAGE OIL