The ianuacoeli is the gate of heaven which every good Christian should pass through to enter the mater ecclesia. This is why the tree of life is placed in a doorway, because it indicates the path of purification that people must take to reach Salvation. A kind of threshold that, once crossed, allows you to see the light of God. In fact, Palermo’s tree of life culminates in the large ten-ray rose window with a man’s face in the central tondo. The pilgrim, now purified, can enter the church, since they have left the darkness behind him.