The document discusses the Byzantine Empire and its capital Constantinople. Constantinople was ideally located for defense as it was surrounded by water on three sides and had fortified walls. It also lay at a strategic crossroads for trade between Europe and Asia. Life in Constantinople was more advanced than in Western Europe, with public services and a sewer system. Emperor Justinian rebuilt parts of the city after a rebellion and improved infrastructure. He also codified Roman law, the basis for modern legal codes. The state religion was Eastern Orthodox Christianity, which was closely linked to the government. The emperor had authority over the church and religion played a central role in daily life.