The procession in St. Peter's Basilica today is one of the most picturesque features of the Western Liturgy as celebrated in the Basilica.
The canons process around the inside nave after they have the blessing of the candles.
A symbolic presentation of the truth proclaimed in the Canticle of Simeon when he proclaimed that Christ is the, "Light for the revelation of the Gentiles."
The anthems sung during this procession, Eastern in origin, express the joy and gladness of this happy festival as well as the honor and praise we give to our blessed Lady and her Divine Son by its devout observance.
For meditation, read the Canticle of Simeon (Luke 2:29-32): Nunc dimittis servum tuum, Domine!