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.

Belgrade is the capital and largest city of Serbia. It is located at the confluence of the Sava and Danube rivers and at the crossroads of the Pannonian Plain and the Balkan Peninsula. The population of the Belgrade metropolitan area is 1,685,563 according to the 2022 census. It is one of the major cities of Southeast Europe and the third most populous city on the Danube river.