 A still more resonant aspect of 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 . A devastating outbreak of bubonic plague in the early 540s marked the end of an age of splendour . 
