The Meeting of Waters (Portuguese: Encontro das Águas) is the confluence between the Rio Negro, a river with dark (almost black coloured) water, and the sandy-coloured Amazon River or Rio Solimões, as it is known the upper section of the Amazon in Brazil. For 6 km (3.7 mi) the river's waters run side by side without mixing. It is one of the main tourist attractions of Manaus, Brazil. This phenomenon is due to the differences in temperature, speed and water density of the two rivers.