The Kalemegdan complex is the main historical place in Belgrade. In addition to the fortress itself, there is a zoo, an amusement park for children, playgrounds, a bandstand, a dinosaur park, lots of fountains and places to walk. Stunning views from the fortress of the Danube and Sava rivers (the fortress is located at the confluence of these rivers). When staying in Belgrade, it is difficult not to visit Kalemegdan. I highly recommend it.
Probably one of the most visited places in Belgrade. History lovers are recommended first of all. The fortress is huge, and the view from its walls to the Danube is simply mesmerizing, especially in summer.
During the day and in the evening, huge crowds of locals and tourists sit in the park and stroll along the fortress walls.