The Trombetas is a river on the northern side of the Amazon River. Its confluence with the Amazon is just west of the town of Óbidos, Pará in Brazil. Its sources is in the Guiana highlands, but its long course is frequently interrupted by violent currents, rocky barriers, and rapids. The inferior zone of the river, as far up as the first fall, the Porteira, has but little broken water and is low and swampy; but above the long series of cataracts and rapids the character and aspect of the valley completely change, and the climate is much better.