The river and its tributaries flow through the Congo Rainforest, the second largest rain forest area in the world, second only to the Amazon Rainforest in South America. The river also has the second-largest flow in the world, behind the Amazon; the second-largest drainage basin of any river, behind the Amazon; and is one of the deepest rivers in the world, at depths greater than . Because its drainage basin includes areas both north and south of the equator, its flow is stable, as there is always at least one part of the river experiencing a rainy season.