On December 9, 1531 Juan Diego had the first or four visions of a young Aztec princess who appered to him on the Tepeyac Hill outside of Mexico City. Speaking in Nahuatl, his native language she requested that a church be built in her honor on that site. Realizing he had a vision of the Blessed Virgin he went to the archbishop of Mexico City to deliver her message. The Archbishop told him to go back and ask the young woman for a sign. The first sign was the miraculous healing of Juan Diego's uncle. The second was the miraculous presence on non-native Castillian roses on the otherwise baren Tepeyac Hil in the middle of winter. The thid was the image of the young woman which appeared on the Juan Diego's mantle which he used to bring the roses to be Archbishop. As a result, the Archbishop believed and built a church dedicated to Our Lady on the site.
Our Lady of Guadalupe is the patroness of Mexico and the Americas. Her feast is celebrated on December 12.
The Mosaic of Our Lady of Guadalupe was created by the Vatican Mosaic Studios after the miraculous image which appeared on Juan Diego's mantle. This mantle is preserved in the Basilica of Our Lady of Guadalupe in Mexico City.
The Mosaic can be found in the Shrine of Our Lady of Guadalupe in the south/west corner of the church, to your left upon entering through the main doors.