This is the 10151st most frequent Russian word.
бельгийской
"Belgian" (adjective, relating to Belgium).
The word 'бельгийской' is used as a female adjective referring to 'живописи' (paintings) in the genitive case, describing their origin as Belgian.
В музее представлена выставка бельгийской живописи.
The museum features an exhibition of Belgian paintings.
Here, 'бельгийской' is a female adjective modifying 'шоколадки' (chocolate) in the genitive case, denoting that the chocolate is of Belgian origin.
Я попробовал кусочек бельгийской шоколадки.
I tried a piece of Belgian chocolate.
In this sentence, 'бельгийской' is used as a female adjective describing 'столице' (capital) in the prepositional case, specifying the location as being in the Belgian capital.