It's not all that uncommon for a town or village to be built at the bottom of a valley between mountains. Often the reason for this is a water source that flows there. One such place in Italy, according to a recent io9.com article, found themselves without sunlight for several months out of the year and finally decided to do something about it, building a giant mirror to capture sunlight and redirect it into the town. Think about what some enterprising folk in your tabletop roleplaying setting might do along these lines as you check out the trailer for a movie made on this situation. Enjoy!