Europe’s second longest river and the former frontier of the Roman Empire, the Danube flows through several major cities—though few more charming than the capital of Serbia. From scenic riverwalks and floating bars to secluded beaches and wild islands, Belgrade’s pretty Danube banks promise sights and adventure for any city visitor. In the territory of Belgrade, the Danube flows through a length of 60 km, and represents the heart of summer happenings.