Rome a few decades before Augustine’s time.  Note especially the the vast size of both the aqueduct and the Circus Maximus!  Other large cities where Augustine lived – Milan, Carthage – would have looked similar.  Just as Western architecture and urban design are predominant in the world today, the rest of the Empire followed Rome in the early Christian era.  320, of course, is only 7 years after the Edict of Milan legalized Christianity.  One big difference between this landscape and the landscape of Augustine’s time would have been an increase in the number of Christian churches.