Answer: Justinian was responsible for the construction of the Hagia Sophia, the center of Christianity in Constantinople. Even today, the Hagia Sophia is recognized as one of the greatest buildings in the world. Justinian also systematized the Roman legal code that served as the basis for law in the Byzantine Empire.
Emperor Justinian I was a master legislator. He reorganized the administration of the imperial government and outlawed the suffragia, or sale of provincial governorships. He also sponsored the Codex Justinianus (Code of Justinian) and directed the construction of several new cathedrals, including the Hagia Sophia
Some of his most notable achievements include Belisarius and Justinian's reconquering of lost territories, Justinian's Code which unified the empire under a single set of laws, and his Rebuilding of Constantinople into one of the best cities there ever was, after the Nika revolt destroyed most of it.
Hope this helps!
