Cais do Valongo, or Valongo Wharf, was recently designated a world heritage site. It's an old stone pier in Rio de Janeiro built for the landing of almost one million enslaved Africans in the 19th century. It was unearthed a few years ago and has brought to the fore difficult questions about the legacy of the slave trade. Fernando Duarte of BBC Brasil, who's from Rio, feels it's a story that's been hidden from view for too long.

Image: People passing the Valongo slave wharf in Rio de Janeiro, Brazil.