whatever the case, "the cambridge ancient history" notes that the occasion of her presence in rome were the vicennalia of constantius ii, a celebration in honor of completing twenty years on the throne. constantius and his milan court moved to rome for the occasion, marking the first and only known visit of this particular augustus in the ancient capital of the roman empire. constantius was following the examples of diocletian and constantine i who also visited rome during their own vicennalia. the presence of constantius, eusebia and helena marked this as a dynastic display.