This is the 5819th most frequent Polish word.
zamkowego
"Zamkowego" means "of the castle" or "castle-related" in English.
In this sentence, 'zamkowego' is an adjective formed from 'zamek' (castle), modifying 'ogrodu' (garden) to indicate its association with the castle.
Spacerowaliśmy wokół zamkowego ogrodu.
We walked around the castle's garden.
Here, 'zamkowego' is again an adjective derived from 'zamek' (castle), now describing 'strażnika' (guard) to specify that the guard is associated with the castle.
Podziwiałem zamkowego strażnika podczas mej wizyty.
I admired the castle's guard during my visit.
In this sentence, 'zamkowego' functions as an adjective related to 'zamek', qualifying 'pokoju' (room) to indicate it belongs to the castle.