When the Colonna pope, Martin V, ‘returned’ the papacy to Rome in 1420, what sort of city did he find? It was not encouraging: a handful of churches, a rebellious aristocracy in their semi-fortified palaces in a less than salubrious quarter of a once glorious city, over which ancient ruins stood in silent watch, partially exposed and largely forgotten. So how was it transformed so radically and is so short a time? Humanist scholars and antiquarians from Leon Battista Alberti to Flavio Biondo reimagined the glories of ancient Rome via a systematic analysis of its surviving monuments. Stimulated by these energetic scholars, a succession of popes, cardinals and princely families set to work in an attempt to emulate, indeed outdo the Rome of Augustus and the Empire as it became the Rome of the Popes and the ‘Church Triumphant’. The results are still with us: the Apostolic Palace in the Vatican, Palazzo Venezia, the Ponte Sisto bridge across the Tiber River and the Via Giulia are the pre-eminent examples of this lavish patronage.