This is the 863rd most frequent Russian word.
московской
"Московской" means "of Moscow" or "Moscow's" in English.
Here, 'московской' is used as an adjective in the genitive case, qualifying the noun 'реки' (river), indicating a belonging or relation to Moscow.
Я наслаждаюсь видами московской реки.
I enjoy the views of the Moscow river.
In this sentence, 'московской' is an adjective in the genitive case modifying 'архитектуры' (architecture), showing a characteristic or style related to Moscow.
Это старинное здание московской архитектуры.
This is an ancient building of Moscow architecture.
Here, 'московской' is an adjective in the prepositional case, describing the noun 'школе' (school), denoting its location in Moscow.