Mountains are an essential element of a Christmas village and can be created using various materials such as paper mache, clay, and Styrofoam. Paper mache is an inexpensive and easy-to-use material that can be molded into any shape. Start by cutting out pieces of paper and soaking them in water. Once the paper is wet, apply it to the base of the mountain and then cover it with a thin layer of glue. After the glue dries, you can add layers of paper mache until you achieve the desired height and shape. For extra texture, you can use paint or sand to create a rocky surface.