It is one of the tributaries on the right bank of the Amazon River. It originates from two other rivers: the Beni (which comes from Bolivia) and the Mamoré. It is navigable, and runs through Porto Velho, the capital city of the State of Rondônia. There is a huge treasure lying beneath its muddy waters: one of the world's largest gold reserves. The Transamazon Highway crosses it, as it also crosses the Tapajós and Xingu Rivers.
