Pope Benedict is spending his final hours as the head of the Catholic Church after announcing his resignation earlier in February.
The 85-year-old says his strength is failing after nearly eight years as pontiff. He is the first pope to abdicate since Gregory XII in 1415.
After a last night in the papal apartments, Benedict on Thursday takes leave of his cardinals, including 115 still below the age of 80 who will choose his successor in March.
A few are under pressure not to take part because of their alleged role covering up sex abuse by clergy, the BBC reports.
The Pope spent much of Thursday inside the Vatican and will hand temporary charge of the world's 1.2 billion Roman Catholics to Cardinal Tarcisio Bertone before flying by helicopter to Castel Gandolfo, the papal summer residence, near Rome.
At 8pm (local time), he will cease to be the Pope - a moment marked symbolically when the Swiss Guards at the gate of Castel Gandolfo march off for their return to the Vatican.
The German pontiff, born Joseph Ratzinger, will continue to be known as Benedict XVI, with the new title of "pope emeritus".
In his retirement, he will wear a simple white cassock rather than his papal clothes and swap his famous red shoes - the colour is symbolic of the blood of the early Christian martyrs - for brown.
His "Fisherman's Ring", the special signet ring which contains the Pope's name and is impressed to validate certain official documents, is expected to be destroyed along with the lead seal of the pontificate.
The long-time theologian is expected eventually to retire to a monastery on a hill inside Vatican City, with officials saying he will not be able intervene publicly in the papacy of his successor, though he may offer advice.
On Wednesday, an estimated 150,000 people packed into St Peter's Square for the Pope's final general audience.
Benedict admitted he faced "choppy waters" during his eight years at the helm of the Catholic Church, but says he was guided by God and felt his presence every day.
He told the crowd his papacy had been "a heavy burden", but accepted it because he was sure that God would guide him. At times he "felt like St Peter with his apostles on the Lake of Galilee".
The Pope thanked his flock for respecting his decision to retire, saying he was standing down for the good of the Church.
"I took this step (resignation) in full awareness of its gravity and novelty but with profound serenity of spirit."