by 476. The Western Empire was replaced by the so-called barbarian kingdoms, with the Arian Christian Ostrogothic Kingdom ruling Rome from Ravenna. The resultant cultural fusion of Greco-Roman, Germanic, and Christian traditions formed the foundations of the subsequent culture of Europe. 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. The middle of the 6th century was characterized by extreme climate events (the volcanic winter of 535–536 and the Late Antique Little Ice Age) and a disastrous pandemic (the Plague of Justinian in 541). The effects of these events in the social and political life are still under discussion. In the 7th century the disastrous Byzantine–Sasanian War of 602–628 and the campaigns of Khosrow II and Heraclius facilitated the emergence of Islam in the Arabian Peninsula during the lifetime of Muhammad. Subsequent Muslim conquest of the Levant and Persia overthrew the Sasanian Empire and permanently wrested two thirds of the Eastern Roman Empire's territory from Roman control, forming the Rashidun Caliphate. The Byzantine Empire under the Heraclian dynasty began the middle Byzantine period, and together with the establishment of the later 7th century Umayyad Caliphate, generally marks the end of late antiquity. Terminology The term Spätantike, literally "late antiquity", has been used by German-speaking historians since its popularization by Alois Riegl in the early 20th century. It was given currency in English partly by the writings of Peter Brown, whose survey The World of Late Antiquity (1971) revised the Gibbon view of a stale and ossified Classical culture, in favour of a vibrant time of renewals and beginnings, and whose The Making of Late Antiquity offered a new paradigm of understanding the changes in Western culture of the