This is the 12241st most frequent Polish word.
miastu
"Miastu" means "to the city" or "for the city" in Polish.
In this sentence, "miasta" is used in the genitive case to indicate movement toward the city.
Zbliżamy się do miasta.
We are approaching the city.
Here, "miastu" is the dative case, indicating giving aid to (the city).
Pomagam miastu w organizacji festiwalu.
I am helping the city with organizing the festival.
In this sentence, "miastu" is used in the dative case, indicating the indirect object of the action (the recipient).