Ceiling Panel in Nave
This panel of the Cathedral's beautifully painted ceiling depicts the Papal Tiara and the crossed keys (Matthew 16:18-19) which appear together on the Holy See Coat of Arms and on the flag of Vatican City. These are symbols of the papacy and are thus a call to Christian unity under the legitimate authority of the Successor of St. Peter.
Pray for Pope Benedict XVI. They don't call him "The Pope of Christian Unity" for nothing. It can be done.