During the reign of Hadrian (117-138), Roman architecture reached peaks never reached before, both because of the extention of the professional activity of Apollodorus of Damascus (in all likelihood the true designer and executor at least of the Pantheon’s dome) and because of the Emperor’s deep interest in architectural design, which probably led him to a direct involvement. It is in fact conceivable that Hadrian personally designed the most innovative buildings of the imperial praedia (Hadrian’s Villa, Horti Sallustiani and Baia), where he introduced formal freedom, design audacity and lexical innovations not to be found in constructions not linked to the figure of the Emperor-Architect. It is practically obvious that he approved the form and decoration of the main buildings built during his reign, especially in Rome and Athens. It is certain that his interest was the driving force behind the exceptional development of architecture in practically all the provinces of the Empire: imperial teams spread schemes and models that can still be identified today, leaving the continuation and completion of the works to the local initiative. Such a fervor of construction sites ensured the persistence of forms, styles and technologies from the Hadrian age at least until the Severian age, and in some cases even beyond.