mountains, Rondônia and Mato Grosso estados (“states”), west-central Brazil. Rising out of the tropical rain forests of Rondônia, near the Bolivian border, the range extends southeastward for 500 miles (800 km) to the vicinity of Diamantino in Mato Grosso. Its northwestern section consists of rolling plateaus, which rise to more than 2,300 feet (700 m) above sea level in the southeast. On its northern and western slopes rise the Juruena and Guaporé rivers, both tributaries of the Amazon; from the range's southern flanks come headwaters of the Paraguay River.