For decades Aussie families camped at 'Tent land', unaware of what lay beneath them.

Aboriginal and Torres Strait Islander readers, please be advised that this work includes images and names of deceased people.

In the northeastern corner of Rottnest Island lies a patch of tree-lined grassland. It’s a place where hundreds of Australian families have pitched their tents, camping chairs and BBQs on idyllic summer getaways.

But for decades, these holidaymakers remained unaware that beneath that well-trodden patch of earth lies one of Australia’s largest mass burial sites.

The remains of at least 373 people remain there in unmarked graves, the first of which was unearthed in 1971. All are in a seated position, all are men, all are Aboriginal.

This place, once known as ‘Tent land’, is now bordered by a thin rope fence and is protected under law by the 1975 Aboriginal Heritage Act. But it serves as a vital reminder about the dark history of this island paradise.

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A century before it was a holiday destination, Rottnest Island – or Wadjemup to the Noongar people – served another purpose: a prison for the thousands of Aboriginal people being rounded up by authorities across mainland Western Australia.

As Noongar woman and former member of the Rottnest Island Board, Karen Jacobs, told the ABC, after colonisation of the Swan River area in 1829 her people were suddenly forced off their country to make room for pasture.

“[The settlers] cleared the land and blocked all the freshwater springs that ran through the city. This meant all the medicinal plants, all of the traditional vegetation and animals were all gone. Our whole hunting ground was gone within three years of settlement,” she said.

Settlement came with a strange new legal system that clashed with the her people’s ancient methods of governance and customary law. Land suddenly belonged to an individual, as did the animals that walked upon it, meaning traditional hunting and gathering could now be seen as trespassing or theft.

Many of those who fell foul of the new laws were chained together, marched hundreds of kilometres and shipped to Rottnest Island.

According to the Rottnest Island Authority, at least 4000 Indigenous men and boys were incarcerated there, the first of which quarried and stacked the limestone that would hold those that came after them.

Conditions were horrid. Disease was rife, and by the 1880s there were up to 10 men in each 1.7m x 3m cell. Most of those later found buried at 'Tent land' had perished from measles, influenza and malnutrition.

On top of it all, the prison's long-reigning superintendent Henry Vincent is believed to have subjected inmates to horrific torture and abuse.

"There's evidence he got clips and ripped a prisoner's beard clean out. Another time he beat a prisoner to death with a set of keys,” Dr Glen Stasiuk, lecturer & senior Indigenous researcher at Murdoch University, told ABC.

"He had no problem with shooting prisoners if they didn't do as they were told. He chained them up at night with a long pole system. It was hell on earth."

The octagonal prison building, known as The Quod, operated exclusively as a 'native prison' right up until 1903 and then as an ordinary jail until 1932. It was then turned into a holiday lodge, one of many catering to Rottnest Island's booming tourism trade.

But as of May 31 2018, that changed. After three decades of campaigning led by the Aboriginal community, the building ceased operating as accommodation and was returned to the management of the Rottnest Island Authority. Plans for the site are yet to be finalised, but will ensure that "Aboriginal history of Rottnest Island is appropriately interpreted for today’s visitors, and the state’s Aboriginal community."

As Iva Hayward-Jackson, chair of the Rottnest Island Deaths Group Aboriginal Corporation, notes, the site represented personal agony for the inmates, devastation for their families and communities, but today is an opportunity for reconciliation.

"All Australians but especially people who visit Wadjemup need to wake up to what happened there. That’s the only way they can have a genuine experience of the place. It doesn’t mean you can’t go and have a nice holiday. It means you can have an authentic physical, mental and spiritual encounter with history.

"That’s what reconciliation is; that’s what we want."