"The Spirit of the Sacred Liturgy during Advent, full of the joyful announcement of approaching freedom, is one f holy enthusiasm, tender gratitude and an intense longing for the coming of the Word of God in the hearts of all the children of Adam.
The Introit gives eloquent expression to the feelings of humanity, cast down, yet full of hope, and begs the Saviour to bring it back into the path which leads to Bethlehem, along the way of truth and justice The epistle calls upon us to rouse from sleep. The Church in the Gospel the second coming of Ohr Lord at the end of the world with His first appearance at Bethlehem as Our Reedemer.
Man is made up of spirit and flesh, and whilst the former is desirous of being drawn to truth and love, the latter understand only such good or evil as can be percieved by the senses, and must be held in check by penance and by a fear of the judgements of God. -- SM"
The Missal notes that the "Station" for the Mass would be at St. Mary Major.
In the glory days of the Church, certainly from th time of Poope Gregory the Great, and possibly before - the people used to gather at difference churches depending what the feast, occasion was. It's well worth checking out this article about Stational Masses here.