Questions & Answers about U planini postoji duboka pećina.
Why is the subject duboka pećina placed at the very end of the sentence?
This shows how Croatian handles new information. Just like English uses 'There is a...' to introduce something new, Croatian often moves the subject to the end of the sentence. This final position, called the rheme, signals to the listener that the deep cave is the new, key piece of information being introduced to the story.
How would the meaning change if the word order was Duboka pećina postoji u planini?
Moving the subject to the beginning makes it the 'known' information. The translation shifts from 'There is a deep cave in the mountain' to 'The deep cave is located in the mountain.' The focus of the sentence changes from introducing the cave to telling the listener where this specific, already-known cave is.
Why do we use the verb postoji here instead of a form of biti (to be)?
While you could technically say U planini je duboka pećina, using the verb postojati (to exist) is a very common and natural way to state that something is present or exists in a location. It perfectly captures the English 'there is / there are' when introducing physical places, objects, or even abstract concepts like problems.
As a quick refresher, why does the preposition u trigger the locative case (planini) here rather than the accusative (planinu)?