They began queueing before dawn to view the German theologian’s body, which was transferred early Monday 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 queue that snaked around the edge of the vast St Peter’s Square.
READ ALSO: Former pope Benedict XVI dies aged 95
Benedict led the Catholic Church for eight years before becoming the first pope in six centuries to step down in 2013, citing his declining health.
His successor Pope Francis will lead the funeral on Thursday in St Peter’s Square before his remains are placed in the tombs beneath the basilica.
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 the church, 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”.
Benedict died at the Mater Ecclesiae monastery where he had lived for the past decade, his last words in the early hours of Saturday said by the Vatican to have been “Lord, I love you!”
His body will lie in state for three days, with members of the public allowed in during the day, passing first through the metal detectors used routinely to screen visitors to St Peter’s 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” — 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 that it will include delegations from Italy and Germany.
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.