They began queueing before dawn to view the German theologian's body, which was transferred early in the morning from the monastery in the Vatican grounds where he died on Saturday aged 95.
"I arrived at 6:00 am, it seemed normal to come and pay homage to him after all he did for the church," said an Italian nun, Sister Anna-Maria, near the front of the line that snaked around the vast St Peter's Square.
Benedict led the Catholic Church for eight years to 2013 before becoming the first pope in six centuries to step down, citing declining health.
People wait in line to pay respect to Pope Emeritus Benedict XVI at St Peter's Basilica in the Vatican, on January 2, 2023.
Photo credit: Andreas Solaro | AFP
His successor Pope Francis will lead the funeral on Thursday in St Peter's Square before Benedict's remains are placed in the tombs beneath the basilica.
He will be buried in the tomb which held Pope John Paul II's remains until 2011, Vatican spokesman Matteo Bruni said Monday.
Benedict's body, dressed in red papal mourning robes and a gold-edged mitre, was laid out on a catafalque draped in gold fabric in front of the altar of St Peter's, flanked by two Swiss Guards.
Many of those filing past took pictures on their smartphones, while some prayed or made the sign of the cross.
"The atmosphere is very intimate," Francesca Gabrielli, a pilgrim from Tuscany in central Italy, told AFP inside the basilica.
She said Benedict was "a great pope, profound, unique".
Some 65,000 people paid their respects Monday, according to the Vatican.
Benedict died at the Mater Ecclesiae monastery where he had lived for the past decade. His last words in the early hours of Saturday were said by the Vatican to have been "Lord, I love you!"
Members of the public are allowed to view the body during day-time, passing first through the metal detectors used routinely to screen visitors to the basilica.
Among the visitors Monday were curious tourists, including Valerie Michalak, on holiday with her family from Benedict's native Germany.
"It's a once in a lifetime chance to be part of this big ceremony," she said.
Thursday's funeral is unprecedented in modern times in that it will be presided over by a sitting pontiff.
Benedict's shock resignation created the extraordinary situation of having two "men in white" -- both him and Francis -- at the Vatican.
Papal deaths usually trigger the calling of a conclave of cardinals to elect a successor, but this time Francis remains in post and will lead proceedings.
The Vatican has yet to release details of the guest list, beyond saying it will include delegations from Italy and Germany.
Commemorative framed pictures of late popes Benedict XVI (right and centre) and Pope John Paul II (left) are seen at a shop in the Vatican, on January 2, 2023.
Photo credit: Tiziana Fabi | AFP
Spain’s royal household said former queen Sofia, wife of ex-king Juan Carlos I, would attend the funeral. Polish President Andrzej Duda will also be present.
Italian Prime Minister Giorgia Meloni, who at the weekend joined world leaders from Joe Biden to Vladimir Putin in paying tribute to Benedict, was among the first to visit his body on Monday morning.
She was greeted by Archbishop Georg Gaenswein, Benedict's long-time aide.
The last papal funeral, of John Paul II in 2005, drew a million faithful and heads of state from around the world.
But Benedict has been an ex-pope for longer than he was pontiff -- and he was a more divisive figure.
People wait in line to pay respect to Pope Emeritus Benedict XVI laying in state in St Peter's basilica in the Vatican, on January 2, 2023.
Photo credit: Andreas Solaro | AFP
A brilliant theologian, he alienated many Catholics with his staunch defence of traditional values and as pope struggled to impose his authority on the church as it battled a string of crises, including over clerical sex abuse.
His successor cuts a very different figure, an Argentine Jesuit who is most at home among his flock and has sought to forge a more compassionate church.
Pope Francis paid tribute to Benedict in three New Year's events at the Vatican over the weekend, "thanking God for the gift of this faithful servant of the Gospel and of the Church".
Francis, 86, has raised the prospect that he might follow Benedict's example and one day resign.
In July, suffering knee problems that have forced him to rely on a wheelchair, he admitted he needed to slow down or think about stepping aside.
Last month, Francis revealed he had signed a resignation letter when he took office should poor health prevent him from carrying out his duties.
