The nephew of Justin I, he became co-emperor of his uncle in April 527 and sole emperor in August of the same year. He is also known as the Great due to both his internal reforms and external expansions. During his reign both North Africa and Italy were reconquered as well as some part of the Iberian Peninsula. In the East he was faced by Persian aggression under Khosrow I. Justinian I was also responsible for reform of Roman Law resulting in the Corpus Iuris Civilis. He also faced internal turmoil, namely the Nika revolt, during which large parts of Constantinople were destroyed. He had the city rebuilt with the most famous building being the Hagia Sophia. He died in 565.