Concurrently, the continuity of the Eastern Roman Empire at Constantinople meant that the turning-point for the Greek East came later, in the 7th century, as the Eastern Roman, or Byzantine Empire centered around the Balkans, North Africa (Egypt and Carthage), and Asia Minor. The degree and extent of discontinuity in the smaller cities of the Greek East is a moot subject among historians. The urban continuity of Constantinople is the outstanding example of the Mediterranean world; of the two great cities of lesser rank, Antioch was devastated by the Persian sack of 540, followed by the plague of Justinian (542 onwards) and completed by earthquake, while Alexandria survived its Islamic transformation, to suffer incremental decline in favour of Cairo in the medieval period.