praefectus urbi (prefect of the city)
(later referred to as the eparch of the city) Αdministrator and virtual governor of Constantinople in the Early/Middle Byzantine Era. He was responsible for the surveillance and the harmonius life of the Capital. One of his responsibilities was to control the commercial and manufacturing activities of Constantinople. After 1204, however, the office began to diminish, while from the 14th century, his responsibilities were assumed by two officers, the so-called kephalatikeuontai of the capital.

praetorian prefecture (praefecura praitorio)
In Late Roman Empire it was the basic administrative unit. Prefectures were estabished by Constantine I (4th century). The Empire was then divided to four praetorian prefectures: i) praefectura praetorio per Orientem (prefecture of Oriens), ii) praefectura praetorio Galliarum (prefecture of Galliae), iii) praefectura praetorio per Illyricum (prefecture of Illyricum), iv) praefectura praetorio Italiae, Illyrici et Africae (prefecture of Italia and Africa).