What were Justinian's achievements?

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He created a code of law that helped unite the Byzantine Empire and later served as a model for the codes of law in many modern nations.
He moved the imperial capital from Rome to Byzantium, so it would attract people from all over the world.
He built a huge domed cathedral called the Hagia Sophia, an enormous underground aqueduct, and a fabulous palace complex.
He doubled the size of the empire and ruled much of the Mediterranean world.