Justinian I (482 - November 14, 565) was the Eastern Roman emperor from 527 to 565. During his reign, Justinian sought to revive the empire's greatness and reconquer the lost western half of the historical Roman Empire. His legacy was the uniform rewriting of Roman law, the Corpus Juris Civilis, which is still the basis of civil law in many modern states. His reign also marked a blossoming of Byzantine culture, and his building program yielded such masterpieces as the church of Hagia Sophia. Undated mosaic.