What were emperor justinians main achievements?

Emperor Justinian I, who reigned from 527 to 565 AD, is best known for his ambitious efforts to reconquer lost territories of the Western Roman Empire, significantly expanding the Byzantine Empire. He also commissioned the "Corpus Juris Civilis," or the "Code of Justinian," which systematized Roman law and influenced legal systems in many modern nations. Additionally, Justinian oversaw the construction of the Hagia Sophia, a monumental architectural achievement that remains a symbol of Byzantine culture and artistry. His reign is often marked by efforts to strengthen the central authority of the emperor and promote Christianity.