Portuguese sea captain Diogo Cão finds the mouth of the Congo River.

Diogo Cão, also known as Diogo Cam, was a Portuguese mariner and one of the most notable explorers of the fifteenth century. He made two voyages along the west coast of Africa in the 1480s, exploring the Congo River and the coasts of present-day Angola and Namibia.

The Congo River, formerly also known as the Zaire River, is the second-longest river in Africa, shorter only than the Nile, as well as the third-largest river in the world by discharge volume, following the Amazon and Ganges rivers. It is the world's deepest recorded river, with measured depths of around 220 m (720 ft). The Congo–Lualaba–Luvua–Luapula–Chambeshi River system has an overall length of 4,700 km (2,900 mi), which makes it the world's ninth-longest river. The Chambeshi is a tributary of the Lualaba River, and Lualaba is the name of the Congo River upstream of Boyoma Falls, extending for 1,800 km (1,100 mi).