On December 9, 1531, Mary appeared on a hill just outside Mexico City in Mexico to Juan Diego. She asked that a shrine be built there.
Juan told the bishop and the bishop asked for a sign that it was really Mary that asked for the shrine to be built.
Juan returned to Mary and told her of the bishop's request. Mary told Juan to gather roses from the hill and take them to the bishop as his sign.
It was December and not time for the roses to bloom but Juan found many beautiful roses. He began gathering them up and put them in his tilma (A covering over clothes).
He carried them back to the bishop. He explained what Mary had said to him and presented the bishop with the sign he had asked for. As he unfolded his tilma, the roses fell to the floor. As the roses fell, there on his tilma, was an image of Mary, the Mother of God.
The chapel was built in 1535.
Many people feel this is what Mary really looks like since she put this image on the tilma. Notice underneath, holding Mary, is St. Michael the archangel.