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.
Oyo Empire or Oyo-oro). The two most important structures in Oyo-Ile were the 'Afin,' or palace of the Oba, and his market. The palace was at the center of the city close to the Oba's market called 'Oja-Oba'. Around the capital was a tall earthen wall for defense with 17 gates. The importance of the two large structures (the palace and the Oja Oba) signified the importance of the king in Oyo. Oyo had grown into a formidable inland power by the end of the 14th century. For over a century, the Yoruba state had expanded at the expense of its neighbors.