The Belgrade Fortress, consists of the old citadel and Kalemegdan Park on the confluence of the Sava and Danube rivers, in an urban area of modern Belgrade, Serbia. Located in Belgrade's municipality of Stari Grad, the fortress constitutes the specific historical core of the city. As one of the most important representatives of Belgrade's cultural heritage, it was originally protected right after World War II, among the first officially declared cultural monuments in Serbia. The fortress was declared a Monument of Culture of Exceptional Importance in 1979, and is protected by the Republic of Serbia. It is the most visited tourist attraction in Belgrade, with Skadarlija being the second. Since the admission is free, it is estimated that the total number of visitors is over 2 million yearly.

Singidunum was an ancient city which later evolved into modern Belgrade, the capital of Serbia. The name is of Celtic origin, going back to the time when the Celtic tribe Scordisci settled the area in the 3rd century BC, following the Gallic invasion of the Balkans. Later on, the Roman Republic conquered the area in 75 BC and incorporated it into the province of Moesia. It was an important fort of the Danubian Limes and Roman Legio IV Flavia Felix was garrisoned there since 86 AD. Singidunum was the birthplace of the Roman Emperor Jovian. It was sacked by Huns in 441, and by Avars and Slavs in 584. At the beginning of the 7th century, the Singidunum fort was finally destroyed.