Friuli Venezia-Giulia has been an important link between Italy and eastern Europe for a long time. Some of the most ancient human traces in Europe are from 400.000 years ago and were found right on Carso sinkholes. In the caves nearby were found as well traces of neanderthalensis hunters and human traces from Upper Paleolithic. It's plenty of farmers settlements from early Neolithic in Friuli Venezia-Giulia, mixed up with peoples from Po Valley and Balkan regions.
Few walled sites called "castellieri" are from metallic ages, some of them has been even preserved since Roman age. The area was inhabited by two large ethnic groups: Gauls-Carnian people were based in Friuli instead of Venezia-Giulia inhabited by Istrians.
These two populations has been on fight between each other for a long time before to be annexed to Roman Empire on II-I Century AD. Romans found few main centers as Aquileia and Grado that were crucial crossing points for communications with eastern european regions.