علي بن يوسف
The intricate ribbed dome in front of the mihrab is considered a highlight of Almoravid architecture and dates to the renovation of Ali ibn Yusuf. The structure of the dome is strictly ornamental, consisting of multiple ribs or intersecting arches forming a twelve-pointed star pattern. It is also partly see-through, allowing some outside light to filter through a screen of pierced and carved arabesque and openwork decoration that fills the spaces between the ribs.