This is the 9036th most frequent Polish word.
stadionu
"Stadionu" means "of the stadium" (genitive case of "stadion").
The word 'stadionu' is in the genitive case here, indicating motion towards the stadium.
Do stadionu prowadzi długa aleja.
A long avenue leads to the stadium.
Here, 'stadionu' is used in the genitive case, expressing the object of negation ('I don't see').
Nie widzę stadionu z tego miejsca.
I can't see the stadium from here.
In this sentence, 'stadionu' is in the genitive case, showing proximity ('near the stadium').