This is the 7060th most frequent Russian word.
белграде
"Белграде" is the prepositional case of "Белград," meaning "Belgrade," the capital city of Serbia.
Here, the word 'Белграде' is in the prepositional case, indicating the location where the action occurred (in Belgrade).
Я был в Белграде прошлым летом.
I was in Belgrade last summer.
In this sentence, 'Белграде' again appears in the prepositional case, used to specify the location associated with the action of being or visiting.
Находясь в Белграде, я посетил исторические места.
While in Belgrade, I visited historical sites.
The word 'Белграде' is used in the prepositional case, within a phrase explaining the topic of a conversation or discussion.