O Encontro das Águas.
The meeting of the waters, is where the Rio Negro flows into the Rio Solimões to form the Amazon River.
The Solimões comes from the Brazilian-Peruvian border, down from the Andes. It is light brown in color. The Rio Negro originates in eastern Colombia, and then joins the Orinoco in Venezuela, and when it enters Brazil it receives the name Rio Negro. It is colder, heavier, slower-moving and very acidic compared to the Solimões. It is due to these differences that they flow side by side without mixing for several kilometers, and thus the meeting of the waters occurs. This is a must for tourists that come to Manaus.
And traveling on a boat down the river admiring this phenomenon is how I celebrated my birthday this year.