Possibilty of Fawcett's 'Z'!?
I hope the film doesn't go off into absurdites; the costar was in a truly ludicrous Brazil jungle movie a few years back.
However, in 175_? some Portagees wandering in the Bahia mountains and found a partially demolished city, with statues of seeming age. The previous night they had camped outside, awaiting dawn to investigate. When the sun went down,a flapping of wings signalled hundreds of bats rising out of the city to hunt. I imagine the Portagees didn't sleep soundly that night. In Rio archives a report of this is filed under Report #512.
In 1984, the city was rediscovered; named Ingrejil. That's an very old place lost for hundreds of years, and Bahia is on the Atlantic coast, not deep in the Orinoco or Mato Grasso. The fabled Machu Picchu, far higher than Mexico City, wasn't found until 1911. Explorers are still hunting Akakor, yet another Inca city. So the jungle overgrown illusion of Fawcett, may still be found; All it takes is an "Indie", and a bit o' luck.