That snow covered mound with a door is a cellar. Such a great invention! For a few weeks we have had temperatures down to -10 .. -25 degrees Celsius. Yet, without any electricity, without any man-made heating inside the cellar the temperature stays above freezing. Today I went to fetch potatoes from the cellar, and was delighted to see that everything is fine in there. So, the layer of soil surrounding the cellar is enough of insulation to protect it from freezing.