I would start at Kalemegdan. From here you see the Sava meeting the Danube, New Belgrade across the water and the old center behind you. Geography stops being a list of names.
Then walk Knez Mihailova toward Republic Square and drift into Skadarlija or Dorćol. It is a strong first day without turning sightseeing into competitive pin collecting.
Belgrade gets better when you stop collecting sights and start collecting neighborhoods.
Day 1 · Old Belgrade
Give Kalemegdan a couple of hours. The fortress changed over centuries, so the interest is in the whole historical layer above the rivers rather than one monument.
Continue through Knez Mihailova, Republic Square and Dorćol. A coffee stop is part of the route, not a planning failure.
Day 2 · Zemun
Zemun was a separate town until 1934 and still feels distinct. Climb through Gardoš, wander the old streets and come back down to the Danube.
Morning
Go to Gardoš early while the old lanes are still quiet.
Evening
Return to the center for Skadarlija or a quieter Dorćol dinner. Skadarlija has atmosphere, but it does not hold a monopoly on Belgrade cooking.
Day 3 · Dome, concrete and water
Start at the Temple of Saint Sava, then choose between the Nikola Tesla Museum and the large-scale modernist architecture of New Belgrade.
Finish by the river or at Ada Ciganlija. After a dense center, water and trees beat another museum.
Kalemegdan
Fortress, park and the clearest view of the city's geography.
Zemun
Gardoš, old streets and the Danube.
Saint Sava
A monumental temple and a reason to walk Vračar.
New Belgrade
A completely different scale and architecture.
What to eat
Start with burek, then move to ćevapi or pljeskavica with kajmak and ajvar. Portions are not known for shyness.
What I would skip
Do not spend the entire trip inside the Knez Mihailova-Skadarlija bubble.
- Do not reduce Zemun to a twenty-minute photo stop
- Do not treat Skadarlija as the only food district
- Do not default to taxis when the city network is free
Bottom line
Three days are enough to understand Belgrade's layout.
Leave blank space in the schedule. The city works well without a stopwatch.
The blank space will probably become coffee and something grilled.
