Aus dem Link in #1 (dort auch Fotos) :
Refrigeration Before the Refrigerator
... At least as far back as the Middle Ages, using refrigeration to preserve food was normal. Farmers who were fortunate enough to have a cave on their property would use it for storing and prolonging the life of milk, cheese, and other produce.
Those who didn’t have a cave would hang a pitcher in the well to keep their milk below ground, where it was cooler.
This eventually evolved into man-made caves – more commonly known as root cellars. Thus, the root cellar can rightly be called the first man-made refrigerator.
Working well in pretty much any climate, the root cellar relies on the same principle as a cave: that it is always cooler underground. ...