The Rio Negro, the largest left tributary of the Amazon River and the largest blackwater river in the world, has its sources along the watershed between the Orinoco and the Amazon basins. It also connects with the Orinoco by way of the Casiquiare Canal. The Rio Negro ends in the Amazon River at Manaus, Brazil.
The Rio Negro is navigable for 450 miles above its mouth. In the wet season, it overflows, sometimes to a breadth of 20 miles, and becomes a succession of lagoons, full of long islands and intricate channels. While the name Rio Negro means Black River, its waters are not exactly black, they are similar in color to clear tea.
Journeys trips that include the Rio Negro:
Information based on http://en.wikipedia.org/wiki/Rio_Negro