The co-cathedral contains many treasures, among them two splendid altarpieces, the fruit of the early activity of the Sienese painter Francesco Vanni, The Immaculate Conception and Saint John the Baptist in the Desert. The first altar in the right aisle holds The Immaculate Conception, dated 1588. The canvas, originally placed over the altar of the Immaculate Conception in the ancient Romanesque church, was commissioned to Vanni by the cathedral provost Fulvio Bucelli. The work is distinguished not only by the bright colors and delicate forms typical of Sienese painting of that period, but also by its complex Marian symbolism. The Virgin is placed in a beautiful miniaturized landscape where every element is rich in meaning. Starting from the lower right corner, we see the “spotless mirror” (Wisdom 7:26) that refers to her Immaculate Conception; the lily (Song of Songs 2:1-2), emblem of purity; the spring, symbol of life; the “enclosed garden” (Song 4:12), a sign of her virginity; the morning star (Rev 22:16), since Mary, in her holiness, is the first fruit of Christ’s salvation; the door of Heaven (Gen 28:17) and the stairway to Paradise (Gen 28:12-13), in that she is the path of access to her Son; the ivory tower (Song 7:5), symbol of her perpetual virginity; the tower of David (Psalm 60:4), a reference to Mary’s fortitude; the temple of the Holy Spirit (Luke . . .