Which empire conquered Mediterranean area?
In the west, no empire followed it for some three hundred years.
In 800, the Frankish King, Charlemagne, who had conquered much of
Italy, was crowned "Roman Emperor" by the Pope. This was the
beginning of the "Holy Roman Empire" which continued until 1806,
though after Charlemagne's death its authority was usually limited
to Germany and Italy, and became increasingly nominal even there.
In the East, the Roman Empire (commonly called the "Byzantine"
Empire) continued until 1453, when it was replaced by the Ottoman
Empire, whose Sultan used the title "Qaysar y Rum" (Emperor of
Rome) and which survived until 1922. Between the early 600s and
800s about half the former Roman Empire (Syria, Egypt, N Africa,
Spain) was included in the Arab Caliphate, which also held other
lands as far as the borders of India and China. The Tsars of Russia
claimed to be the heirs of Byzantium and the "Third Rome", but
never ruled any significant amount of Roman or Byzantine
territory