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.
Spanning 155 miles, the circles, squares and other geometric shapes form a network of avenues, ditches and enclosures built long before Christopher Columbus set foot in the new world. Some date to as early as 200 AD, others to 1283.