Fulcrum of the decorative enterprise of the pontiff's private chapel, of intimate beauty and profound and complex theological significance, the canvas with the Annunciation by Guido Reni stands out on the altar. The ray of light of the Holy Spirit pierces the clouds and illuminates the face of Mary kneeling who welcomes the divine message with folded arms, while Gabriel hands her the lily, symbol of her purity, pointing to the sky, populated by little angels, and the figure of God the Father in the arch that preludes the event in a glory of angels. A mystery, announced by the patriarchs and prophets, which has its epilogue in the luminous dome with God the Father with the Virgin in glory among musician angels.