The Belgrade Fortress (), consists of the old citadel (Upper and Lower Town) and Kalemegdan Park (Large and Little Kalemegdan) 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 (foreign, domestic, citizens of Belgrade) is over 2 million yearly. Location Belgrade Fortress is located on top of the high ending ridge of the Šumadija geological bar. The sandbank stretches at least from the city's Tašmajdan section, originating from the Miocene period, and the oldest stages of the ancient Pannonian Sea. The cliff-like ridge overlooks the Great War Island () and the confluence of the Sava river into the Danube, and makes one of the most beautiful natural lookouts in Belgrade. It borders the neighborhoods of Dorćol (north and north-east), Stari Grad (east) and Kosančićev Venac (Savamala; south). It is bounded by 3 streets: Boulevard of Vojvoda Bojović, Tadeuša Košćuška, Pariska, plus the railway along the riverside. History Classical Antiquity Belgrade Fortress is the core and the oldest section of the urban area of Belgrade. For centuries, the city population was concentrated only within the walls of the fortress, and thus the history of the fortress, until most recent times, reflects the history of Belgrade itself (see: Timeline of Belgrade history). The first mention of the city is when it was founded in the 3rd century BC as "Singidunum" by the Celtic tribe of Scordisci, who had defeated Thracian and Dacian tribes that previously lived in and around the fort. The city-fortress was later conquered by the Romans, was known as Singidunum and became a part of "the military frontier", where the Roman Empire bordered "barbarian Central Europe". Singidunum was defended by the Roman legion IV Flaviae, which built a fortified camp on a hill at the confluence of the Danube and the Sava rivers. In the period