Valiya Hamza from Brazil's National Observatory said researchers found indications the subterranean river is 3,700 miles (6,000 kilometers) long, about the same length as the Amazon on the surface.
He said the existence of an underground river that also flows west to east would mean that the Amazon rain forest has two drainage systems.
To contemplate that something like that could go unnoticed for this long. Really cool find, God knows what they may find if they explore that. Very interesting.
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