"Today, from the earthly nature, a Heaven has been formed on earth"

The gospel writers do not tell us where Mary was born. We only know that she was related to Elizabeth who lived in Judea. So it is quite  possible that she herself was born in Jerusalem, as an ancient tradition tells us, based on the apocryphal Gospel of James, which gives us details about the Virgin's parents, Joachim and Anne.

There was in Jerusalem a house called "the House of Anne" near the pool of Bethsaida. A church was later built near this house and dedicated on September 8: the Basilica of the Nativity of Mary, renamed the Church of St. Anne in the 12th century.

The anniversary of this dedication was commemorated every year. The feast spread to Constantinople in the 5th century and then to the West. Later, the feast of Mary's conception, set to nine months earlier, was added to it, which explains why the feast of the Immaculate Conception falls on December 8.

The Nativity of Mary is one of the great feasts of the Byzantine liturgical year because it inaugurates the economy of salvation and the entry of the Word of God into human history: "This day is the prelude to universal joy. On this day the winds of salvation have begun to blow" (Byzantine Liturgy).

It was in the Basilica of the Nativity of Mary that St. John Damascene, Father and Doctor of the Church (d. 749) proclaimed: "Come, all of you: with joy let us celebrate the joy of the whole world! Today, from the earthly nature, a Heaven has been formed on earth. Today is for the world the beginning of Salvation!"

Source:  Swiss Catholic Portal