The Kalemagdan Fortress is a really cool site. there are so many interesting places that I, even though I visited it as a kid, still discover something new to this day.
When you come next time, across from the entrance to Kalemegdan, at the end of Knez Mihajlova Street, under the shopping center in Rajiceva, you have a large parking lot. The hour is expensive, but at least you have a place to park.

In recent years, food has "lost" its taste, considering how expensive the prices in restaurants have become, but let me know if you're passing by, so I can give you the name of a restaurant where you still eat quality and not so expensive food.