The office survived the collapse of the Western Roman Empire, and the last urban prefect of Rome, named Iohannes, is attested in 599.
The praefectus urbi was appointed each year for the sole purpose of allowing the consuls to celebrate the Latin Festival, which required them to leave Rome.
The office's powers also extended beyond Rome itself to the ports of Ostia and the Portus, as well as a zone of one hundred Roman miles (c. 140 km) around the city.
[3][4] The provisioning of the city's large population with the grain dole was especially important; when the Prefect failed to secure adequate supplies, riots often broke out.
In late Antiquity, the office gained in effective power, as the imperial court was removed from the city, meaning that the prefects were no longer under the emperor's direct supervision.
The office was usually held by leading members of Italy's senatorial aristocracy, who remained largely pagan even after Emperor Constantine the Great's conversion to Christianity.
[7] In such a capacity, Quintus Aurelius Symmachus played a prominent role in the controversy over the Altar of Victory in the late 4th century.
The urban prefecture survived the fall of the Western Roman Empire, and remained active under the Ostrogothic Kingdom and well after the Byzantine reconquest.
[7] When the Emperor Constantine the Great (r. 306–337) named Constantinople the capital of the Roman Empire, he also established a proconsul to oversee the city.
Correspondingly, on 11 September or 11 December 359, Constantinople was also granted an urban prefect, commonly called in English the Eparch from his Greek title (ὁ ἔπαρχος τῆς πόλεως, ho eparchos tēs poleōs).
In 535 the praitōr of the demoi (πραίτωρ τῶν δήμων; praetor plebis in Latin), who commanded 20 soldiers and 30 firemen, was put in charge of policing and firefighting, while in 539, the office of the quaesitor (κοιαισίτωρ) was established and tasked with limiting the uncontrolled immigration to the city from the provinces, with supervising public mores, and with prosecuting sexual offenders and heretics.
In addition, there were the heads (γειτονιάρχαι, geitoniarchai, the old curatores regionum) and judges (kritai) of the city's districts (Latin regiones, in Greek ρεγεῶναι, regeōnai), the parathalassitēs (παραθαλασσίτης), an official responsible for the capital's seashore and ports, as well as their tolls, and several inspectors (epoptai), the heads of the guilds (exarchoi) and the boullōtai, whose function was to check and append the seal of the eparch on weights and scales as well as merchandise.