The Belgrade Fortress (Belgrade Fortress) is the core historical landmark of Belgrade, the capital of Serbia. It is located in the strategic highland at the intersection of the Sava and Danube rivers, known as the "key of the Balkans". Its history dates back to the early fortifications built by the Celtic in the 3rd century BC, and was later rebuilt and competed for many times by Rome, Byzantine, Ottoman, Austro-Hungarian Empire, and was listed as a special protected cultural relics of Serbian state level in 1979. As a strategic fortress in Europe, the fortress of Belgrade witnessed more than 2000 years of conflict and integration: from the Roman Legion garrison, Ottoman siege, to the fire of modern world wars, the masonry structure of its city walls clearly presents the architectural technology of different periods. Known as "open-air history textbook". The Sava River and Danube River interchange have a wide view and are the best place to take a panoramic view of the city; the classic seat is next to the Victors Memorial. It is recommended to go in the evening and enjoy the sunset on the riverside.