This is the 2805th most frequent Russian word.
риге
"Риге" is the dative case or prepositional case of "Рига," meaning "Riga," the capital of Latvia.
Here, 'Риге' is the locative (prepositional) case of 'Рига', used to indicate the location.
Я был в Риге прошлым летом.
I was in Riga last summer.
In this sentence, 'Риге' is again in the locative case, used here to indicate the topic of conversation.
Мы говорили о Риге и её истории.
We talked about Riga and its history.
'Риге' is used in the locative case to describe what is present in the location.