Pilgrims flocked to bid a final farewell to the frail 85-year-old, who abruptly cut short his pontificate eight years in by declaring he was too weak to keep up with the modern world. "I have come in gratitude for everything he has done these past eight years," said Father Giulio, a 67-year-old priest from the Abruzzo region.
"Resigning is a powerful message for every Christian. He resigned without bitterness but instead in sweetness and serenity," he said.
One group of faithful held up a banner reading: "Benedict, we'll miss you!". Another sign said: "The pope is the heart of this city!" This will be the pope's last major public outing. There were more than 100,000 people in and around the famous Vatican plaza, where city authorities have installed metal detectors, deployed snipers on Vatican rooftops and set up field clinics.
The weekly audience, which is exceptionally being held in St Peter's Square because of the high numbers of pilgrims, is usually a mix of prayers and religious instruction from the pope. The Vicar General of Rome, cardinal Agostino Vallini, said residents of the Italian capital would turn out in great numbers because they felt a special bond with the ageing pope.
"It is something our heart and our faith demands," Vallini told Vatican Radio ahead of the event. "Rome likes the pope a lot and feels a special affection for him so it could not miss his last public act," he said. Benedict will be the first pope to step down since the Middle Ages -- a break with Catholic tradition that has worried conservatives but kindled the hopes of Catholics around the world who want a breath of new life in the Church.
Rome has been gripped by speculation over what prompted Benedict to resign and who the leading candidates might be to replace him, as cardinals from around the world fly in ahead of the conclave to elect his successor. Rumours and counter-rumours in the Italian media suggest cut-throat behind-the-scenes lobbying, prompting the Vatican to condemn what it has called "unacceptable pressure" to influence the papal election.
Campaign groups have also lobbied the Vatican to exclude two cardinals accused of covering up child sex abuse from the upcoming election conclave.