A special and very beautiful prayer tradition is associated with the last seven days of Advent in the Catholic Church. The Vespers prayers for December 17 - 23 each include what is called an O Antiphon particular to each day (so called because each antiphon begins with the vocative "O," followed by a title associated with Christ, derived from Scripture). In the post-Vatican II liturgy of the Church, the O Antiphons are also used during the Alleluia verses corresponding to each day. In Medieval English tradition, the O Antiphons included an eight one, with the sequence starting on Dec 16 to allow for the addition.
Below, I include a video rendition of each antiphon. To read more, visit the Wikipedia entry on the O Antiphons.
December 17: O Sapientia
As mentioned above, in Medieval English tradition, the O Antiphons started on December 16 and an 8th one was added on December 23. (Please note: The video below inaccurately states that this antiphon was used on December 24).
Photo Credit: The 14-pointed star marking the site of the birth of Christ inside the Church of the Nativity in Bethlehem by Zoltan Abraham (c) 2016.