Emona (Latin: Colonia Iulia Aemona) was a Roman civil town, built on the site of an old indigenous settlement on the territory of the present Ljubljana. The Roman Emona sites in Ljubljana can be seen in several parts west of the old town centre. It is also the setting of a popular novel The Stranger in Emona [Tujec v Emoni] (1978) by .
Emona's ground plan was 430 metres times 540 metres and was surrounded by city walls, which were 6 to 8 metres high and 2.5 metres thick. The Emona city wall was built between 14 and 15 AD, the southern city wall was redesigned in 1930s by the architect.
Emona had a population of 3,000 to 5,000 people, mostly farmers, landlords and merchants, including a small number of government officials and war veterans. Its streets were paved and its houses were built of stone with the hypocaust underfloor heating system, and connected to a public sewage system. The remains of a baptistery with a pool, mosaics, and part of portico may be seen at Erjavčeva 18, next to Cankarjev dom Culture and Congress Centre.