In the preleased game, roman town Salona is placed 2 regions further north than its actual location (it was situated within nowday town of Solin, a small town right next to the city of Split). This town is in the same region as Spalatum, and since Salona was a mayor centre at the time, it deserves to be the main town in the region.
Spalatum, or nowday Split was a simple village until the end of 3rd century AD when roman emperor Diocletianus decided to build his palace in his home region, but that is another story.