Candido Rondon found the River of Doubt, now the Rio Roosevelt, which flows in this country's Amazonas State
Maj Percy Fawcett ... [PAR] Not far north of the Roosevelt river bridge in Rondonia state the world richest .... 
mix up with the Great Rio Negro river on the north side of the Amazon flowing out 
of .... down the River Of Doubt through Rondonia, Mato Grosso and Amazonas.