Croatia is divided into 20 counties and City of Zagreb as presented on images below
Wikipedia page for Croatian counties
Counties are grouped in 4 regions
There are also 4 major airports (Zagreb, Split, Dubrovnik, Osijek) that could be used as lines of connection or as separate territories
As a line of connection there is Adriatic Sea ferry called "Jadrolinija" which connects cities Rijeka -> Split -> Dubrovnik
I think this could be really playable map