The late medieval fortification of the feudal ruler of herceg Stjepan Kosaca is the most monumental archeological site of the Ljubuški Municipality, located on the prominent top of the karst chain of Buturovica hill (396 m above sea level) and as such is a symbol of the townof Ljubuški and Herzegovina. The fort complex consists of two parts. The central tower of the rectangular shape, popularly called "Herceguša", built in the late 14th or early 15th centuries and a perimeter wall in the shape of an irregular polygon with massive towers, dating from the Ottoman period after 1472. The complex covers an area of 3,350 m2 and consists of several units, such as a small and large steeple with a table and various buildings; guardhouse, granary, bakery, armory, gunpowder and 4 water tanks.