There’s More than Just Belgrade
It's important repeating that a country is more than just its most popular tourist attraction. Exploring beyond the city or a popular tourist attraction reveals considerably more aspects of a region than you may otherwise expect. This is especially true of Serbia, which is why it's at the top of my Serbia travel recommendations. Belgrade is cosmopolitan at times and gritty urban at others, but neither of these characteristics can be found elsewhere.
For starters, there are the rural areas and little villages of Fruska Gora, which are worlds distant from Belgrade's urban environment. Even neighboring cities like Novi Sad and Sabac have distinct personalities. It's worth noting that Serbia isn't exactly small, so there are probably more places to visit than you think. It is a city break in Belgrade which is only one of many possible Serbia itineraries.