Nowadays, we tend to use the term Late Antiquity to describe the final period of the Roman Empire and the changes associated with it. Although the final centuries, from the reign of the Severans until the ultimate fall of the Western Empire in the fifth century, are traditionally seen as a time of progressive decadence, the restructuring undertaken by Diocletian (284—305), and then by Constantine (307—337), signalled a clean break with the period of invasions that had characterized the second half of the third century. Their reigns saw a decisive centralization of power as well as the development of an imperial court, not only in Rome but also in Trier, Milan, Sirmium, Constantinople and even Ravenna. Constantine brought the Tetrarchic period to an end by making Christianity the official religion of the Empire. Ecclesiastical institutions very soon came to play an important role in urban life, as the episcopal form of church government became established. The Church sought to promote its image and Christianize the arts, including public and private monumental sculpture.