Tens of thousands of people are expected to pay their respects to former Pope Benedict XVI when his lie-in-state begins later at the Vatican.
He died on New Year’s Eve at the age of 95, nearly a decade after he retired from ill health.
Pope Francis will preside over Thursday’s funeral – the first time a pope has been buried by his successor.
The Vatican says the service will be simple, solemn and quiet.
Benedict XVI became the first pope in 600 years to resign citing ill health in 2013.
Hello’s body will be displayed in an open casket at St Peter’s Basilica for three days, with people allowed to pay their respects until 7pm each evening.
The Pope Emeritus will be laid to rest in St Peter’s Square before being laid to rest in the mausoleum beneath the basilica.
The Vatican released photos of the body on Sunday, dressed in a red papal cassock and gold-trimmed peacoat.
Tributes have poured in from around the world, and thousands are expected to attend the funeral.
Pope John Paul II’s final funeral, which took place in 2005, was one of the largest Christian gatherings in history, drawing an estimated four million people to Rome.
The arrangements for the service are still unclear, as many of the traditions associated with the death of a serving pope are not required – particularly the selection of a successor.
Vatican spokesman Matteo Bruni told reporters that Benedict asked that the funeral be marked simply.
Details of the guest list have not been released but the Vatican has said it will include delegations from Italy and Benedict’s native Germany.
Pope Francis paid tribute to his “dearest” predecessor after his death.
US President Joe Biden praised the former pope for his “lifelong devotion to the Church”, while Italian Prime Minister Giorgia Meloni hailed him as “a great man” who history will not forget.
In Brazil – the world’s largest Catholic nation – incoming president Luiz Inacio Lula da Silva said he wanted “consolation for the faithful and admirers of the Holy Father”.
Pope Benedict has been a controversial figure, and some have criticized him for failing to deal with allegations of religious sexual abuse.
