Excavations in the southern Portuguese city of Lagos unearthed a huge 15th-century landfill site a few years ago. Alongside a variety of implements, the archaeologists found human remains. There were more than 150 skeletons in all, of men, women and children—and some of them were tied up.

Genetic analysis confirmed that they were the skeletons of Africans who had been enslaved by traders and brought to Portugal. Perhaps they died during the voyage or shortly after their arrival; in any case, they were not given a proper burial. This shocking discovery exposed the concealed history of Portugal. Over the course of four centuries, six million people were transported in this way under the Portuguese or Brazilian flags.

In Tales of Oblivion, Dulce Fernandes investigates the traces left in today’s landscape by this horrific trade in human beings. The calm camera tracks steadily from site to site—the former landfill is now a parking garage topped by a minigolf course—and museum objects bearing witness to the history of colonialism. In a quiet but thorough way, this essayistic film reveals a hidden past.