in the first century ad, romans won the area of banja luka, which was then inhabited mainly members of mezeji, an illyrian tribe. this area was completely within the roman province called illyricum. today, the city of banja luka is located on the road that led from dalmatia to pannonia, or from salona to today's bosanska gradiška. today's citadel kastel, which is in what was the center of the city at the time, was a roman military fortress.