Who was Justinian and what contributions did he make?

Justinian I was a Byzantine Emperor who reigned from 527 to 565 AD. He is best known for his efforts to reconquer lost territories of the Roman Empire, as well as for his ambitious legal reforms, most notably the compilation of the "Corpus Juris Civilis," or "Body of Civil Law," which laid the foundation for modern legal systems in many countries. Additionally, he is credited with significant architectural achievements, including the construction of the Hagia Sophia, which remains a masterpiece of Byzantine architecture. Justinian's reign marked a peak in Byzantine culture and power.