Belgrade Fortress is the oldest section of the urban area of Belgrade standing at the confluence of the Danube and the Sava Rivers. For centuries the city population was concentrated only within the walls of the fortress. Founded in the 3rd century BC by a Celtic tribe, the fortress was later conquered by the Romans. In the period between AD 378 and 441 the Roman camp was being repeatedly destroyed in the invasions by the Goths and the Huns. The legend says that Attila's grave lives here.