According to legend, the tribes were taken to a land on the far side of the Sambatyon River, which raged with a current so violent that it could not be crossed and, by some accounts, burned with fire.
Needless to say, a river of fire must be a fabrication of pure mythology.
But not if you ask Andrés Ruzo. In a recent Ted Talk, Dr. Ruzo describes how he followed a family folktale deep into the Amazon forest to discover a river fed by a geothermal hot spring with an average temperature of 86 degrees Celsius.
(Not quite boiling, but much hotter than your extra-hot coffee, which is about 60 degrees.)
Modern technology allows us to do things that were once the realm of science fiction and sorcery. Modern discoveries are showing us that the legends of the past may have more truth to them than we ever imagined possible.