There are many columns around the world dedicated to Mary, this one in Rome is under the title of the Immaculate Conception. It was erected shortly after the Dogma of the Immaculate Conception was promulgated.
Mary is shown with representations of the four evangelists along with her typical artistic calligraphy as the Immaculate Conception.
Since the column itself was originally raised by the local firemen, the custom of the fire department placing a bouquet at Mary's feet and a floral wreath around her outstretched arm on this date has developed.
Mary's Immaculate Conception, her fiat or let it be done to me at the Annunciation and Jesus' Incarnation in her womb are each important parts of God's wonderful plan for our redemption.