Oyo Empire 17th century, Oyo began a long stretch of growth, becoming a major empire. Oyo never encompassed all Yoruba-speaking people, but it was the most populous kingdom in Yoruba history. The key to Yoruba rebuilding of Oyo was a stronger military and a more centralized government. Taking a cue from their Nupe enemies (whom they called "Tapa"), the Yoruba rearmed with armor and cavalry. Oba Ofinran, Alaafin of Oyo, succeeded in regaining Oyo's original territory from the Nupe. A new capital, Oyo-Igboho, was constructed, and the original became known as Old Oyo. The next oba, Eguguojo, conquered nearly all of Yorubaland.
Yoruba people ancient times, most of these cities were fortresses, with high walls and gates. Yoruba cities have always been among the most populous in Africa. Archaeological findings indicate that Òyó-Ilé or Katunga, capital of the Yoruba empire of Oyo (fl. between the 11th and 19th centuries CE), had a population of over 100,000 people (the largest single population of any African settlement at that time in history). For a long time also, Ibadan, one of the major Yoruba cities, was the largest city in the whole of Sub Saharan Africa. Today, Lagos (), another major Yoruba city, with a population of