High Quality Content by WIKIPEDIA articles! Belgrade Fortress (Serbian Cyrillic: Београдска тврђава), represent old citadel (Upper and Lower Town) and Kalemegdan Park (Large and Little Kalemegdan) on the confluence of the River Sava and Danube, in an urban area of modern Belgrade, the capital of Serbia. It is located in Belgrade's municipality of Stari Grad. Belgrade Fortress was declared Monument of Culture of Exceptional Importance in 1979, and it is protected by Republic of Serbia.