Emona (early Medieval Greek: Ἤμονα)[1] or Aemona (short for Colonia Iulia Aemona) was a Roman castrum, located in the area where the navigable Nauportus[2] River came closest to Castle Hill,[3] serving the trade between the city's settlers – colonists from the northern part of Roman Italy – and the rest of the empire.

The Visigoths camped by Emona in the winter of 408/9, the Huns attacked it during their campaign of 452, the Langobards passed through on their way to Italy in 568, and then came incursions by the Avars and Slavs.

[3] Other ancient Roman towns located in present-day Slovenia include Nauportus (now Vrhnika), Celeia (now Celje), Neviodunum (now the village of Drnovo) and Poetovio (now Ptuj).

Sozomen wrote that when the Argonauts left from the Aeetes, they returned from a different route, crossed the sea of Scythia, sailed through some of the rivers there, and when they were near the shores of Italy, they built a city in order to stay at the winter, which they called Emona.

(The date, although based on legend and poetic speculation, actually fits in both with Herodotus' account and the date of the earliest archaeological remains found so far)[citation needed] According to 1938 article by the historian Balduin Saria, Emona was founded in late AD 14 or early AD 15, on the site of the Legio XV Apollinaris, after it left for Carnuntum, by a decree of Emperor Augustus and completed by his successor, Emperor Tiberius.

In a rectangle with a central square or forum and a system of rectangular intersecting streets, Emona was laid out as a typical Roman town.

[10] Regarding its location within Roman Italy, in 2001 a boundary stone between Aquileia and Emona was discovered in the vicinity of Bevke in the bed of the Ljubljanica River.

[4] The architect Jože Plečnik redesigned the remains of the Roman walls: he cut two new passages to create a link to Snežnik Street (Slovene: Snežniška ulica) and Murnik Street (Slovene: Murnikova ulica), and behind the walls he arranged a park displaying architectural elements from Antiquity, with a stone monument collection in the Emona city gate.

After the Second World War, attempts were made to embed references to Emona grid into modern Ljubljana, with the Roman forum becoming part of the Ferant Park apartment blocks and an echo of the rotunda located along Slovenia Street (Slovene: Slovenska cesta).