Emona or Aemona was a Roman castrum, located in the area where the navigable Nauportus River came closest to Castle Hill, serving the trade between the city's settlers – colonists from the northern part of Roman Italy – and the rest of the empire. Emona was the region's easternmost city, although it was assumed formerly that it was part of the Pannonia or Illyricum, but archaeological findings from 2008 proved otherwise. From the late 4th to the late 6th century, Emona was the seat of a bishopric that had intensive contacts with the ecclesiastical circle of Milan, reflected in the architecture of the early Christian complex along Erjavec Street in present-day Ljubljana.

Italia, also referred to as Roman Italy, was the homeland of the ancient Romans. According to Roman mythology, Italy was the ancestral home promised by Jupiter to Aeneas of Troy and his descendants, Romulus and Remus, who were the founders of Rome. Aside from the legendary accounts, Rome was an Italic city-state that changed its form of government from Kingdom to Republic and then grew within the context of a peninsula dominated by the Gauls, Ligures, Veneti, Camunni and Histri in the North, the Etruscans, Latins, Falisci, Picentes and Umbri tribes in the Centre, and the Iapygian tribes, the Oscan tribes and Greek colonies in the South.