Refrigeration is one of those modern luxuries that most people take for granted, especially considering that the majority of foods have to be preserved using cold to some degree. While it might seem as if refrigeration is a relatively new invention, the idea has been around for thousands of years. Technology has simply allowed refrigeration to reach a new level of efficiency, but it has existed in many simpler forms throughout history. A group of scientists recently discovered that something they had cataloged for years was in fact a rudimentary refrigeration system that functioned in the middle of an arid desert.
The ancients invented a large storage structure called a Yakhchal, and they were constructed in Persia, or what is now present day Iran. These structures were designed to hold cold temperatures by protecting the flow of heat through it. The basic structure involved a subterranean storage center and an above ground conical heat diffuser. They built the structures from a highly heat-resistant mortar that was a mix of clay, sand, ash, egg whites, lime, and even goat hair.
During the winter, water would be allowed to flow down into the bottom of the Yakhchal where it would freeze. The architecture of the buildings allowed that ice to remain frozen as the winter transitioned to summer, and it would create a refrigerated storage area hidden from the heat of summer by the subterranean location of the storage area and the conical heat diffuser above ground. The structures are so efficient they could still be used today.