One of the oldest structures in modern Serbia, which has great cultural and historical significance for the country. It is located on a hilltop 125 meters above sea level at the confluence of the Danube and Sava rivers. History of the Belgrade Kalemegdan Fortress. Judging by archaeological finds, the hill on which the fortress was built has attracted people since the Neolithic era. Traces of primitive settlements have been found here. At this place there were once Celtic, Roman, Byzantine, Hunnic and, finally, Serbian military fortifications.