Flavius Petrus Sabbatius Iustinianus Augustus (c. 482–565 CE), known as Emperor Justinian I, was one of the longest-reigning Roman emperors, known for his splendid building program (of which the Hagia Sophia can still be admired today in Istanbul), the codification of the Roman law, and the reconquest of parts of the former western Roman Empire. As nephew of the childless emperor Jus…