Emperor Justinian I ruled the Byzantine Empire from 527 to 565 AD. He is best known for his ambitious efforts to restore the Roman Empire's former glory, which included military campaigns to reclaim lost territories in the West. His reign also saw significant legal reforms, most notably the compilation of the Corpus Juris Civilis, a foundational work of Roman law. In addition to military and legal achievements, Justinian I is famous for his architectural projects, including the construction of the magnificent Hagia Sophia in Constantinople. His reign marked a period of cultural and artistic flourishing, influencing the development of Byzantine art and architecture for centuries to come.