He recalls the oriental beginnings of Christianity and the figure of St Peter.
It is widely believed that Rome was where Peter spent his final years, and it is from Peter that all Popes trace the authority and symbolism of their office.
But what do we know of his life, and why was Peter the Rock upon whom the Catholic Church was built?
The 5th-century Pope Leo the Great virtually invented the papacy as we know it.
As Rome's secular glory faded, he laid the foundations of an office that was to play a central role in European history.
The papacy of Gregory the Great at the end of the 6th century marked a shift in Christian history.
As the Byzantine world slipped from its grasp, the church turned its eyes northwards.
It was Gregory who launched the mission to England.
The 11th-century monk Hildebrand came from lowly Tuscan roots, but rose to become one of the greatest Popes in history.
As Gregory VII, he set about tackling the corruption which had become endemic in the church and restoring the image of the papacy.
Professor Duffy charts the life of this great reformer who once forced an Emperor to meet him barefoot in the snow, but who ultimately died in exile.
Pope Innocent III was an aristocrat who believed in the high authority of his office.
Yet his energy encouraged the founding of both the Dominican and Franciscan movements, breathing new life into the Europe of the Middle Ages.
Paul III was a great entertainer and Renaissance patron.
His legacy can be seen in Rome's public spaces, but he also led the Catholic Church at the time when its excesses came under attack from Martin Luther and the Protestant North.
Having been dubbed Cardinal Petticoat in his early career, he later came to lay the foundations for the Counter Reformation.
When he was made Pope in 1846, Pius IX was regarded as a liberal.
He held the papal office for longer than anyone else and by the time of his death his reputation was transformed.
Dogmatic and intolerant of dissent, he locked the Catholic Church into a confrontation with the modern world.
Duffy tells the story of how the papacy coped with the spread of democracy.
Pius XII was elected six months before the start of the Second World War, and his response to that conflict has dogged his reputation.
Struggling to remain impartial, Pius failed, in the eyes of many, to speak out strongly enough against the Holocaust.
But has history judged him fairly?
John XXIII reigned for less than five years.
But when he died, The Times commented that few Popes had so captured the world's imagination.
A kindly, laughing old man when he took the papal throne, he immediately astonished the Catholic Church by calling the Second Vatican Council.
Duffy examines the life of the Pope with the vision of a new Pentecost.
The first non-Italian Pope for 450 years, John Paul II survived an early assassination attempt.
Though widely acclaimed for his role in challenging communism, he has been criticised for holding inflexible theological and moral positions.
Duffy looks at John Paul II's achievements in the context of papal history and remembers his final days when Rome came under the international media spotlight.