Sirmium (today Sremska Mitrovica, Serbia), the glorious mother of cities (famously so-called by the ancient historian Ammianus Marcellinus), was an ancient city in Roman Pannonia. Sirmium originally was an Illyrian town conquered by the Romans in the 1st century BC. It was a very important town in the later Roman Empire, being the economic capital of Roman Pannonia and one of the four capital cities of the Roman Empire. The present day region of Srem, Syrmia was named after this city.
Sirmium was one of the oldest cities in Europe.[citation needed] Archaeologists have found a trace of organized human life on the site of Sirmium dating from the 5000 BC. When the Romans conquered the city in the 1st century BC, Sirmium already was a settlement with a long tradition.
In the 1st century, Sirmium gained a status of a colony of the citizens of Rome, and became a very important military and strategic location in Pannonia province. The war expeditions of Roman emperors Traian, Marcus Aurelius, and Claudius II, were prepared in Sirmium.
In 103, Pannonia was split into two provinces: Upper Pannonia and Lower Pannonia, and Sirmium became the capital city of Lower Pannonia.
In 296, Diocletian operated a new territorial division of Pannonia. Instead of previous two provinces, there were four new provinces established in former territory of original Pannonia: Pannonia Prima, Pannonia Valeria, Pannonia Savia and Pannonia Secunda. Capital city of Pannonia Secunda was Sirmium.
In 293, with the establishment of tetrarchy, the Roman Empire was split into four parts; Sirmium emerged as one of the four capital cities of Roman Empire, the other three being Trier, Mediolanum, and Nicomedia. During the tetrarchy, Sirmium was the capital of emperor Galerius. With the establishment of praetorian prefectures in 318, the capital of the prefecture of Illyricum was Sirmium. Sirmium was capital of this prefecture until 379, when the western part of the Praetorian prefecture of Illyricum (including Sirmium) was attached to the Praetorian prefecture of Italia. The eastern part of Illyricum remained a separate prefecture with the capital in Thessalonica under the East Roman Empire.
Since the 4th century, the city was an important Christian centre, and was a seat of the Episcopate of Sirmium. Five Christian councils were held in Sirmium. The city also had an emperor's palace, horse racing arena, mint, arena theatre, theatre, as well as many workshops, public baths, temples, public palaces and luxury villas.
At the end of the 4th century, Sirmium was brought under the sway of the Goths, and later, was again annexed to the Eastern Roman Empire. In 441, Sirmium was conquered by the Huns, and after this conquest, it remained for more than a century in the hands of various Barbarian tribes, such were Eastern Goths and Gepids. For a short time, Sirmium was the center of the Gepide State and the king Cunimund minted golden coins in it. After 567, Sirmium was again included into Eastern Roman Empire. The city was finally conquered and destroyed by Avars in 582. This event marked the end of the period of late Antiquity in the history of Sirmium.