This is the 14953rd most frequent Russian word.
подмосковных
"Podmoskovnykh" means "of the Moscow suburbs" or "located near Moscow."
The word 'подмосковных' is used as an adjective here, modifying 'музеев' (museums), and pertains to places near Moscow.
Мы посетили несколько подмосковных музеев на прошлых выходных.
We visited several suburban museums last weekend.
Here, 'подмосковных' serves as an adjective describing 'лесов' (forests), indicating the geographical location as Moscow outskirts.
Подмосковных лесов славятся своей красотой.
The forests near Moscow are famous for their beauty.
In this instance, 'подмосковных' is describing 'пейзажей' (landscapes), referring again to regions surrounding Moscow.