The remains of the once prosperous and powerful Roman city of Sirmium are concealed beneath the streets of today’s Sremska Mitrovica. The history of the Roman city begins during the Emperor Augustus’ invasion of Illyricum in 35-33 B.C. and continues all the way to 582 A.D. when the city falls under control of the Avars. The Romans probably occupied Sirmium during Tiberius’ wars in Pannonia (13-9 B.C.), and the city was granted the status of a colony (colonia Flavia) under the Flavian dynasty (69-96 A.D.). Sirmium was frequently used as a base for military campaigns against the barbarian groups who continually attacked the frontier in this part of the Empire.
From the time of the granting of colonial status all the way to the end of the fourth century, the ancient literary sources mention Sirmium as a temporary residence for numerous Roman emperors. From the historical sources we know that from the first through the third century Domitian, Marcus Aurelius, Septimius Severus, Maximinus Thrax, Claudius II Gothicus, Probus, Diocletian and the infamous usurpers Ingenuus and Regalian all resided in Sirmium for longer or shorter periods. Five Roman emperors were born in or near Sirmium: Trajan Decius, Aurelian, Probus, Maximianus Herculius and Gratian. The city enjoyed its greatest prosperity at the end of the third and beginning of the fourth century, when it was one of the capitals of the Roman empire and the sometime seat of government for the emperors Diocletian, Licinius, Constantine the Great, Constantius II, Julian, Valentinian, Gratian and Theodosius.
Archaeological excavation in Sirmium has revealed, in addition to the imperial palace and adjacent circus, a number of other monumental public buildings, including the so-called “Licinian Baths,” a granary (horreum) and commercial and industrial areas. Luxuriously appointed urban residences have been discovered, as well as multi-storied apartment buildings (insulae) where the poorer elements of the population lived. The city was protected by a circuit of strong defensive walls and supplied with water by an aqueduct from the Vranjaš spring in Fruška Gora. The city streets were paved, flanked by porticoes and drained with sewers. Coins were struck in an imperial mint in the city and workshops produced various objects in precious metals, glass, and pottery. Bricks were also manufactured there.
The well known Roman historian of the fourth century, Ammianus Marcellinus, described the city as “the famous and populous mother of cities”.