Kinshasa ( formerly LÃ opoldville ) and Brazzaville are on opposite sides of the river at the Pool , where the river narrows and falls through a few cataracts in deep canyons ( collectively known as the Livingstone Falls ) , running by Matadi and Boma , and into the sea at the small town of Muanda . Kinshasa ( formerly LÃ opoldville ) and Brazzaville are on opposite sides of the river at the Pool , where the river narrows and falls through a number of cataracts in deep canyons ( collectively known as the Livingstone Falls ) , running by Matadi and Boma , and into the sea at the small town of Muanda .