Split-Dalmatia County is the central-southern Dalmatian county in Croatia. The administrative center is Split. The population of the county is 455,242. The land area is 4540 km. Physically, the county is divided into three main parts: an elevated hinterland with numerous karst fields; a narrow coastal strip with high population density; and the islands. Parts of the Dinaric Alps, including Dinara itself, form the border with Bosnia and Herzegovina while the Kozjak, Mosor and Biokovo mountains separate the coastal strip from the hinterland. The most important economic activity is tourism. Manufacturing and agriculture are in decline. The county is linked to the rest of Croatia by the newly built four-lane Split-Zadar-Karlovac-Zagreb highway and the Lika railway. Split-Kaštela international airport is used mostly by tourist charter flights in the summer. There is also a smaller paved airfield on the island of Brač. In the hinterland, the larger towns are Sinj, Imotski and Vrgorac . Besides the largest city, Split, the towns on the coast are Trogir, Omiš and Makarska . On the islands, the populations are smaller due to high levels of emigration, but are still mostly urban in character. The main townships are: Supetar on the island of Brač; Hvar town and Stari Grad on Hvar; and Vis town and Komiža on Vis.