To dream that you are in a valley symbolises fertility, abundance, or your need to be sheltered and protected. If you are entering or walking through a valley, then it is analogous to your issues of death and dying. This death may be symbolic as in an end to something in your life. In other words, you are going through a transitional phase. Alternatively, the dream represents life’s struggles and hardships before you can achieve some spiritual enlightenment or epiphany. 

To dream that you are looking down over a valley implies that you have overcome your difficulties and/or limitations.