Pope Benedict XVI arrived in Rome's St Peter's Square aboard his Popemobile Wednesday to greet the huge crowds that had turned up for his last public audience, on the eve of his resignation, dpa reported.
Italian and Vatican authorities were on high alert for an event expected to draw up to 200,000 people, as well as several dignitaries.
The pope is to leave his post at 8 pm (1900 GMT) on Thursday. The Vatican announced Tuesday that he will take the title of "pope emeritus" or "Roman pontiff emeritus" after he steps down.
Benedict is the first pontiff to retire in 600 years. Cardinals will start preliminary meetings to elect a successor early next week, and will set the date for the formal start of a conclave, Vatican spokesman Father Federico Lombardi said.
The Catholic Church's aim is to have a new leader installed before Easter, which this year falls on March 31.