What place did Byzantium occupy in the world at the beginning of the Middle Ages?

What place did Byzantium occupy in the world at the beginning of the Middle Ages? were the assessments of contemporaries who considered Constantinople the center of the inhabited world fair?

The Byzantine Empire at the beginning of the Middle Ages, that is, in the V-VIII centuries, occupied the place of one of the most developed states in the world. In Africa and the Western Hemisphere, there were essentially none, and in Asia there were hardly five: Byzantium proper, Sassanian Iran, the Arab Caliphate, the Harsha Empire in India, the Tang Empire in China and Western Europe, the first significant state can be considered the empire of Charlemagne on the turn of the VIII-IX centuries.
Constantinople could well be considered the center of the inhabited world, given the modest geographical knowledge at that time, for example, in Africa, the territories south of Axum were unlikely to have any permanent contacts with the rest of the world.