Zenit.org has a nice historical piece on the traditional papal procession through Rome to take possession of the cathedrals. Now it is very simple --the Pope arrives through a side entrance and celebrates Mass. But it used to be an elaborate thing --and many of the streets of Rome were altered or designed to accomodate the procession. I like this detail:
"When the dome of St. Peter's was completed according to Michelangelo's plan in 1590, St. Peter's had very different appearance from the basilica we know today. With the immense, tiara-shaped dome standing loftily above rounded apses, it stood as the "head and shoulders" of the Catholic Church. All the churches built along the processional route, from San Giovanni dei Fiorentini on the Tiber, to Santa Maria in Campitelli by the Forum, were crowned with similar domes to show allegiance to the Pope. The effect, as seen from an aerial view, is one of smaller heads following their leader through the city."
