Banja Luka or Banjaluka is the second largest city in Bosnia and Herzegovina. Banja Luka is the traditional centre of the densely-fores…Banja Luka or Banjaluka is the second largest city in Bosnia and Herzegovina. Banja Luka is the traditional centre of the densely-forested Bosanska Krajina region of northwestern Bosnia. According to the 2013 census, the city proper has a population of 138,963, while its administrative area comprises a total of 185,042 inhabitants.