The geography of North Africa has been reasonably well known among Europeans since classical antiquity in Greco-Roman geography. Northwest Africa (the Maghreb) was known as either Libya or Africa, while Egypt was considered part of Asia.
European exploration of Sub-Saharan Africa begins with the Age of Discovery in the 15th century, pioneered by The Kingdom of Portugal under Henry the Navigator. The Cape of Good Hope was first reached by Bartolomeu Dias on 12 March 1488, opening the important sea route to India and the Far East, but European exploration of Africa itself remained very limited during the 16th and 17th centuries. The European powers were content to establish trading posts along the coast while they were actively exploring and colonizing the New World. Exploration of the interior of Africa was thus mostly left to the Arab slave traders, who in tandem with the Muslim conquest of Sudan established far-reaching networks and supported the economy of a number of Sahelian kingdoms during the 15th to 18th centuries.
At the beginning of the 19th century, European knowledge of the geography of the interior of Sub-Saharan Africa was still rather limited. Expeditions exploring Southern Africa were made during the 1830s and 1840s, so that around the midpoint of the 19th century and the beginning of the colonial Scramble for Africa, the unexplored parts were now limited to what would turn out to be the Congo Basin and the African Great Lakes. This "Heart of Africa" remained one of the last remaining "blank spots" on world maps of the later 19th century (alongside the Arctic, Antarctic and the interior of the Amazon basin). It was left for 19th-century European explorers, including those searching for the famed sources of the Nile, notably John Hanning Speke, Sir Richard Burton, David Livingstone and Henry Morton Stanley, to complete the exploration of Africa by the 1870s. After this, the general geography of Africa was known, but it was left to further expeditions during the 1880s onward, notably, those led by Oskar Lenz, to flesh more detail such as the continent's geological makeup.
They also used the Kongo to weaken the neighbor realm of The Portuguese (and later also the Dutch) also became involved in the local slave economy, supporting the state of the Jaggas, who performed slave raids in the Congo.
They also used the Kongo to weaken the neighbor realm of Ndongo, where Queen Nzinga put a fierce but eventually doomed resistance to Portuguese and Jagga ambitions. Portugal intervened militarily in these conflicts, creating the basis for their colony of Angola. In 1663, after another conflict, the royal crown of Kongo was sent to Lisbon. Nevertheless, a diminished Kongo Kingdom would still exist until 1885, when the last Manicongo, Pedro V, ceded his almost non-existent domain to Portugal.
The Portuguese dealt with the other major state of Southern Africa, the Monomotapa (in modern Zimbabwe), in a similar manner: Portugal intervened in a local war hoping to get abundant mineral riches, imposing a protectorate. But with the authority of the Monomotapa diminished by the foreign presence, anarchy took over. The local miners migrated and even buried the mines to prevent them from falling into Portuguese hands. When in 1693 the neighboring Cangamires invaded the country, the Portuguese accepted their failure and retreated to the coast.