In the 6th century, Roman imperial rule continued in the East, and the Byzantine-Sasanian wars continued. The campaigns of Justinian the Great led to the fall of the Ostrogothic and Vandal Kingdoms, and their reincorporation into the Empire, when the city of Rome and much of Italy and North Africa returned to imperial control. Though most of Italy was soon part of the Kingdom of the Lombards, the Roman Exarchate of Ravenna endured, ensuring the so called Byzantine Papacy. Justinian constructed the Hagia Sophia, a great example of Byzantine architecture, and the first outbreak of the centuries-long first plague pandemic took place. At Ctesiphon, the Sasanians completed the Taq Kasra, the colossal "iwan" of which is the largest single-span vault of unreinforced brickwork in the world and the triumph of Sasanian architecture.