The Buzim fort appears in historical documents under two names, Cava and Buzim. The fort of Cavnik or Cavica, stands not far from Buzim in the valley of the river Cava. Although Buzim is one of the largest mediaeval forts in the Krajina (military frontier region) and was of major importance, nothing is known of when it was first built. The construction system suggests that it dates from the 14th century.
The old fort of Buzim is an interesting example of fortifications erected before the age of
firearms with a new set of ramparts and towers built later in the early days of defensive
fortifications against artillery fire. The inner, older fortifications constitute a small citadel forming a relatively regular quadrangle, with tall round towers at the angles. In the late 15th century the citadel was surrounded by new fortifications, trapezoid in plan, with polygonal towers at the angles. The walls and towers of these fortifications are considerably lower, and have emplacements on top for cannon. At the same time, apertures and emplacements for artillery weapons were added to the towers and walls of the inner fortifications. The erection of the outer line of defenses protected the old citadel from direct artillery fire, and the defense approach was fortified, since the towers of the inner fort were taller than the walls of the outer fortifications.