Mountains can symbolize a number of things but are usually about the difficulty of your journey in life. Climbing a steep mountain, especially if it is rocky, indicates that your life is an uphill struggle and always indicates you are on the karmic path.
Being at the top of a very high mountain can indicate that you have reached a point in your life where you feel you can see where you are going. If this is not the case, in reality the dream is predicting that you will get there. This type of dream can also indicate you have the gift of prophecy, as you have such a clear view of everything around you from your high vantage point.