This is the 4056th most frequent Russian word.
московскую
"Московскую" - "Moscow" (feminine accusative form).
The word 'московскую' acts as an adjective, modifying 'культуру' (culture), and agrees in gender, number, and case (accusative singular feminine).
Я изучаю московскую культуру.
I am studying Moscow culture.
Here 'московскую' describes 'газету' (newspaper), and it is in the accusative singular feminine form due to the direct object function of 'газету'.
Он купил московскую газету.
He bought a Moscow newspaper.
In this case, 'московскую' qualifies 'выставку' (exhibition), aligning in gender, number, and case to convey the quality of being associated with Moscow.