It is the second largest river in the world by discharge (after the Amazon), and the world's deepest river with measured depths in excess of 220 m (720 ft). The Congo-Chambeshi river has an overall length of 4,700 km (2,920 mi), which makes it the ninth-longest river (in terms of discharge, the Chambeshi is a tributary of the Lualaba River, Lualaba being the name of the Congo River upstream of the Boyoma Falls, extending for 1,800 km). Measured along the Lualaba, the Congo River has a total length of 4,370 km (2,715 mi). It crosses the equator twice. The Congo Basin has a total area of about 4 million km2, or 13% of the entire African landmass.