In 1996, the bricklayer renovating Merced dos Anjos’ home in Rio de Janeiro told her something strange had happened. Bones appeared as he was breaking ground. As she inspected the site, she found they were human. But why so many bones? Was it the work of a serial killer?

The answer was more macabre. They had unearthed an ancient cemetery. The discovery shed light on the brutal history of Brazil’s slavery past – and Rio’s role as the biggest slavery port in the Americas.

The neighbouring Valongo Wharf, today a World Heritage Site, received roughly one million African captives by 1831. Many were too weak after the transatlantic crossing and died soon after arriving. They were buried in the so-called New Blacks Cemetery.

Merced dos Anjos tells Julia Carneiro how the discovery upended her life and led her to create a research centre to shed light on Rio's painful past.

An Overcoat Media production.

Eye-witness accounts brought to life by archive. Witness History is for those fascinated by and curious about the past. We take you to the events that have shaped our world through the eyes of the people who were there.

For nine minutes every day, we take you back in time and all over the world, to examine wars, coups, scientific discoveries, cultural moments and much more.

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We look at the lives of some of the most famous leaders, artists, scientists and personalities in history, including: the moment Reagan and Gorbachev met in Geneva, Haitian singer Emerante de Pradines’ life and Omar Sharif’s legendary movie entrance in Lawrence of Arabia.

You can learn all about fascinating and surprising stories, like the invention of a stent which has saved lives around the world; the birth of the G7; and the meeting of Maldives’ ministers underwater. We cover everything from World War Two and Cold War stories to Black History Month and our journeys into space.

(Photo: Merced Guimarães dos Anjos. Credit: Julia Dias Carneiro)