From the Catholic News Agency:
White rose petals drifted from the gilded ceiling of St. Mary Major Basilica on Tuesday as Romans celebrated the 1,667th anniversary of a fourth-century Marian miracle that inspired the construction of the oldest Marian sanctuary in the West.
According to tradition, the miracle involved a miraculous snowfall in Rome on Aug. 5 in the year 358. The Virgin Mary appeared to both a wealthy Roman nobleman named John and to Pope Liberius (352–366) in a dream foretelling the August snow and asking for a church to be built in her honor on the site of the snowfall.