The large basilica provides the setting of the small house within the basilica itself. Though the rough walls of the little building have been raised in height and are cased externally in richly sculptured marble, the interior measures only thirty-one feet by thirteen feet.
Within the house an altar stands at one end beneath a statue, blackened over time from the smoke of burning candles and incense, of the Virgin Mother and her Divine Infant. The current statue is a 1920 replacement of damaged ancient original made of cedars of Lebanon. The replacement is made of cedar wood from the Vatican.
The inscription on the altar, Hic Verbum caro factum est, is a reminder that this building is honored by Christians as the house at Nazareth in which the Holy Family lived, and site of the Incarnation, when the Word became Flesh. Another inscription of the sixteenth century which decorates the eastern façade of the basilica sets forth at greater length the tradition which makes this shrine so famous.
Christian pilgrim, you have before your eyes the Holy House of Loreto, venerable throughout the world on account of the Divine mysteries accomplished in it and the glorious miracles herein wrought. It is here that most holy Mary, Mother of God, was born; here that she was saluted by the Angel, here that the eternal Word of God was made Flesh. Angels conveyed this House from Palestine to the town Tersato in Illyria in the year of salvation 1291 in the pontificate of Nicholas IV. Three years later, in the beginning of the pontificate of Boniface VIII, it was carried again by the ministry of angels and placed in a wood near this hill, in the vicinity of Recanati, in the March of Ancona; where having changed its station thrice in the course of a year, at length, by the will of God, it took up its permanent position on this spot three hundred years ago [now, of course, more than 600]. Ever since that time, both the extraordinary nature of the event having called forth the admiring wonder of the neighboring people and the fame of the miracles wrought in this sanctuary having spread far and wide, this Holy House, whose walls do not rest on any foundation and yet remain solid and uninjured after so many centuries, has been held in reverence by all nations.
- from CatholicCulture.org