History of Africa usually governed by an "oba" and an "iwarefa", a council of chiefs who advised the "oba." by the 18th century, the Yoruba city-states formed a loose confederation, with the "Oni" of Ife as the head and Ife as the capital. As time went on, the individual city-states became more powerful with their "obas" assuming more powerful spiritual positions and diluting the authority of the "Oni" of Ife. Rivalry became intense among the city-states. The Oyo Empire rose in the 16th century. The Oyo state had been conquered in 1550 by the kingdom of Nupe, which was in possession of cavalry,
History of the world noted for its art, and the Oyo Empire, the Benin Empire of the Edo people centred in Benin City, the Igbo Kingdom of Nri which produced advanced bronze art at Igbo-Ukwu, and the Akan who are noted for their intricate architecture. Central Africa saw the birth of several states, including the Kingdom of Kongo. In what is now modern Southern Africa, native Africans created various kingdoms such as the Kingdom of Mutapa. They flourished through trade with the Swahili people on the East African coast. They built large defensive stone structures without mortar such as Great Zimbabwe, capital of the