: Facing a Crisis of the Third Century , Emperor Diocletian divided the Roman Empire into East and West to make it more governable.
: He codified Roman law into the Corpus Juris Civilis , but his reign was also marred by the devastating Plague of Justinian , which decimated the population. III. Survival and Transformation (610–1025 AD)
: Justinian commissioned the Hagia Sophia , a feat of engineering that remained the world’s largest cathedral for nearly a millennium.
: Constantine established a new capital at Constantinople (modern-day Istanbul), strategically located on the Bosphorus to control trade between Europe and Asia.