This is the 500th most frequent Latvian word.
baltkrievijā
"In Belarus."
Here, 'Baltkrievijā' refers to the location where the subject resides, using the locative case to express 'in Belarus'.
Es dzīvoju Baltkrievijā.
I live in Belarus.
In this sentence, 'Baltkrievijā' again uses the locative case, indicating the place visited by the person.
Mans kolēģis ir bijis Baltkrievijā.
My colleague has been to Belarus.
Once more, 'Baltkrievijā' serves to specify the planned destination, employing the locative form for the location.