It is the legend that drew legions of explorers and adventurers to their deaths: an ancient empire of citadels and treasure hidden deep in the Amazon jungle.
Spanish conquistadores ventured into the rainforest seeking fortune, followed over the centuries by others convinced they would find a lost civilisation to rival the Aztecs and Incas.
Some seekers called it El Dorado, others the City of Z. But the jungle swallowed them and nothing was found, prompting the rest of the world to call it a myth. The Amazon was too inhospitable, said 20th century scholars, to permit large human settlements.
Now, however, the doomed dreamers have been proved right: there was a great civilisation. New satellite imagery and fly-overs have revealed more than 200 huge geometric earthworks carved in the upper Amazon basin near Brazil’s border with Bolivia.