This chapter shows how the ambivalent status of the Colosseum in early-modern Christian Rome made it a most striking and productive stage for religious ceremonial. It analyses how the emotional intensity of the religious performances was heightened by the sublime ruin and the gory narratives it evoked. The chapter explores how the Colosseum in its turn was transformed, physically as well as conceptually, by the performances. It also shows how the productive conflict between Antiquity and Christianity was dramatized in a ritual interplay–or kind of paragone–between the Colosseum and St Peter's, centre of the Catholic Church. The Colosseum, the largest amphitheatre of the Roman Empire, was constructed between 72 and 80 AD, under the emperors Vespasian and Titus. Stones from the Colosseum were treated as relics which carried with them the grandeur of Ancient Rome the blood of Christian martyrs.