Saint Francis was very aware that all of God's creation is holy and that it reflects his beauty, truth, and goodness. But Francis appreciated churches, especially, because he knew that in these sacred spaces people could find and recognize the presence of God's spirit more easily than "in the world." That is why the Little Poor Man of Assisi dedicated a good portion of his life to rebuilding old abandoned churches, like San Damiano (where he had heard the voice of Jesus Christ) and Saint Mary of the Angels Porziuncola (or Little Portion).
