as their normal place of residence and the city lost its old position as the imperial capital. Diocletian and his colleagues passed their reigns either traveling or in palaces which they maintained elsewhere, closer to the armed frontiers of the empire, in cities such as Nicomedia, Aquileia, or Trier.'The emperor thus escaped the constricting am-bience of a city where he was expected to conduct himself more as a magistrate than as a monarch. 2 By the same token, the way was prepared for the establishment of a new imperial capital to rival the old. The foundation of Constantinople was a result, not the cause, 3 of the declining importance of Rome. Constantine's city fulfilled, in the eastern provinces, a role which Nicomedia had already played in the reigns of Diocletian and Licinius. 4 When the imperial court had departed, many of the former causes of conflict and hostility between emperor and the Senate of Rome disappeared, and the ruler's habitual absence lent his occasional presence an increased significance. 5 The adventus Augusti was no longer a ceremony which heralded permanent residence, but one which presented a rare political opportunity for both parties. Hence any serious attempt to understand or interpret the fourth century cannot avoid inquiring when, why, and under what circumstances emperors visited Rome. However, investigation of the question has been hampered by too ready an acceptance of the statement of a panegyric: