The Meeting of the Waters is included in every boat excursion from Manaus. This is the convergence of Rio Negro’s blackwater and the beige, sandy waves of what Brazilians call Rio Solimões. Others refer to the latter as the Upper Amazon River. The two rivers run in parallel for about 3.7 miles without mixing. This oddity is caused by the difference in the water temperatures, density and speeds of the two rivers. Encontro das Aquas is a visual phenomenon seen in few other places around the world.