Roman emperor
The Western Roman Empire collapsed in the late 5th century. Romulus Augustulus is often considered to be the last emperor of the West after his forced abdication in 476, although Julius Nepos maintained a claim recognized by the Eastern Empire to the title until his death in 480. Following Nepos' death, the Eastern Emperor Zeno abolished the division of the position and proclaimed himself as the sole Emperor of a reunited Roman Empire. The Eastern imperial lineage continued to rule from Constantinople ("New Rome"); they continued to style themselves as Emperor of the Romans (later βασιλεύς Ῥωμαίων in Greek), but are often referred to in modern scholarship as Byzantine emperors. Constantine XI Palaiologos was the last Roman emperor in Constantinople, dying in the Fall of Constantinople to the Ottomans in 1453.
Ostia Antica
After the end of the Western Roman Empire in 476 (traditional date: Julius Nepos died 480 was the last legitimate emperor), Ostia fell slowly into decay as the population of Rome, 700-800,000 in A.D. 400 contracted to 200,000 or less in 500 A.D. The city was finally abandoned in the 9th century due to the repeated invasions and sackings by Arab pirates A naval battle, the Battle of Ostia, was fought there in 849 between Christians and Saracens; the remaining inhabitants moved to Gregoriopolis a short distance away.