What is the difference between in den Bergen and auf den Bergen? We say in die Berge fahren and in den Bergen sein. What about auf die Berge? Does it only refer to mountain climbing and getting to the very top?
literally means on top of/on some mountains, whereas
is denoting a mountaneous region.
An exception would be:
On the other hand, a singular version of (2) can only refer to a mountain's inside.
You would use "auf die Berge" to emphasize getting on the top of mountains - by foot, by bike, by cable car or by something else doesn't matter much.