Karlovac (Croatian: Karlovačka županija) is a county in central Croatia, with the administrative center in Karlovac. The city of Karlovac is another fort from the times of the Military Frontier. It was built as a six-side star fort in the 16th century at the point of confluence of four rivers. The town blossomed in the 18th and the 19th century after being made a free town, with the development of roads between Pannonian plains to the seaside, and waterways along the Kupa river. The 20th century wasn't so favourably inclined, but the city's recovering, once again making use of its crucial geostrategic point in Croatia. The county itself extends towards the north to the water springs of Jamnica, and towards the south all the way down to the mountainous regions of Gorski kotar and Lika, in particular to the Bjelolasica mountain which features the largest winter sport recreation center in the country.