Ah, finally my roman classical lit class comes in handy.

Ausonius, a relatively famous poet http://en.wikipedia.org/wiki/Ausonius wrote the Ordo Urbium Nobilium, which in it lists what he thinks were the top 20 most important cities in the roman empire (with Rome being number 1)

Rome, Constantinople, Carthage, Antioch, Alexandria, Trier, Milano, Capua, Aquileia, Arles, Seville, Cordoba, Tarragona, Braga, Athens, Catania, Syracuse, Toulouse, Narbonne, Bordeaux.