Yesterday, for the solemnity of Pentecost, a venerable custom was performed at the Pantheon, or Basilica of S. Maria ad Martyres. The Italians call this custom "la pioggia di petali di rosa" (or shower/rain of rose petals). While not exclusive to the Pantheon it is without doubt its most famous instantiation. Here is a little bit of history around this tradition and its meaning taken from the Catholic Encyclopedia:
In Italy it was customary to scatter rose leaves from the ceiling of the churches to recall the miracle of the fiery tongues; hence in Sicily and elsewhere in Italy Whitsunday is called Pascha rosatum. The Italian name Pascha rossa comes from the red colours of the vestments used on Whitsunday.It is thought that the origins of this custom specifically at the Pantheon date back to the year 609 when the building was repurposed and consecrated for Christian use after having been given over to Pope Boniface IV by the Byzantine Emperor Phocas.
As the custom stands today, at the conclusion of the liturgy on Pentecost Sunday, the Veni Creator Spiritus is sung while thousands of red rose petals are dropped down through the great oculus (the large opening in the dome). There are many videos that have been made of this impressive sight; here is one of them:
