You can say "(On) Siedzi na ławce w parku" when the park bench is actually located in the park. The same bench placed in the garden would be called "ławka w ogrodzie"
or "ławka ogrodowa" (garden bench) so now you can say:
"(On) Siedzi na ławce w ogrodzie".
Both would be rendered in a single Polish sentence: „Ławka jest w parku”. Polish language does not use articles and most probably the same information would be provided as a context.
That sounds like something that a Russian person would ask, so maybe it's your knowledge of Ukrainian? I don't know if it works the same as Russian. But Polish just needs a verb.