Valongo Wharf in Brazil was discovered by accident in 2011

The worn paving stones discovered under a thick layer of modern concrete in Rio de Janeiro doesn’t look like much at first. But it was here that some million slaves from Africa took their first steps in Brazil.

“It’s a unique memorial, containing the last remaining vestiges of the slaves’ arrival,” said anthropologist Milton Guran. Next week, the UNESCO will consider whether to award what’s known as Valongo Wharf world heritage status, winning protection as a site of global importance.

The wharf, or what remains of it, would join sites like the Taj Mahal in India and the ruined Inca city of Machu Picchu. The UNESCO, which is meeting between July 2-12 in Krakow, Poland, already chose Rio de Janeiro as a heritage site in 2012, recognising the city’s unique combination of landscapes between mountains and the sea.

Today, the Valongo site is not on the water, but well inland, following expansion of the original city. The remains were only discovered by accident in 2011 during works to refurbish the port area for the 2016 Olympics.