A text I am using has the following sentence,
Trenker stammte aus Österreich und drehte viele schöne Filme über die Alpen.
Why is it über die Alpen and not über den Alpen? My guidance for determining whether a preposition gets declined in accusative or dative is determined by whether it addresses the question "wohin" or "wo", respectively. It appears to me that we are talking about "wo" in this case. Is there another justification for this particular declination?
Here, über is used in the sense of about, not in the sense of above. If used in the about sense, it is always used with the accusative case.
In this dictionary entry, this is meaning III.
If the sentence had said "er drehte viele Filme über den Alpen", that would have meant that he shot movies while being above the Alps. That would have been somewhat funny, except if he was maybe in a balloon. The more likely "wo" scenario would have been "in den Alpen". That would have referred to shooting movies while being in the Alps, movies which would not necessarily have been about the Alps.
