Sremska Mitrovica, a city in Northern Serbia, preserves the ruins of the ancient city of Sirmium underneath its streets and squares.
Once a major commercial hub and one of the Roman Empire’s capitals, Sirmium was the birthplace of as many as 5 Roman emperors: Traianus Decius, Aurelian, Probus, Maximianus Herculius and Gratian.This once-powerful Roman city, founded in the 1st century, was host to many Roman emperors over the centuries of its existence including Domitian, Marcus Aurelius, Septimius Severus, Maximinus Thrax, Claudius II Gothicus, Probus and Diocletian.

The city reached its peak in the 3th century CE, when it was declared one of the four capitals of the Roman Empire.
On the archaeological site, you can see the ruins of the imperial palace and the nearby circus (horse racing track), the only of its kind in Serbia, which will give you a glimpse of what life was like in ancient Rome.
The city was protected by massive walls and its richly hued mosaics bear witness to the luxury enjoyed by Roman emperors. The remains of a heating system, which have been discovered underneath almost every room in the palace, speak volumes of the technological advancement of ancient Romans.
The palace was divided into an official area and a residential area, of which the latter is better preserved. The circus, the Roman equivalent of the Greek hippodrome, which was unearthed near the palace, was used for horse racing.
Fragments of the mosaics found on site were made from stone brought in from Asia Minor, Malta, Greece and Italy. The floor mosaics are mainly floral and geometric patterns, with a mosaic depicting the Roman God Mercury standing out as the only figurative image.ŽIn addition to the imperial palace with the circus, at Sirmium you can also see the ruins of the Thermae of Licinius, luxury urban villas, as well as high-rise buildings for common people known as insulae.
Sirmium would later become a Christian stronghold. The preserved remains of a Christian basilica at the heart of the city are a testament to the later stages of Sirmium’s development, before it finally fell to the invading Huns, Goths and Gepids.
To honour the rich Roman heritage of Sirmium, an Oratory Festival is held every year among the ruins of the city’s Roman-era commercial district.

Info: Sirmium