In my search for information about adobe structures around the world, I came across some fascinating information about ancient "refrigerators" in Persia (now Iraq) called "yakhchal." They were being built by 400 B.C. and were used to store food and ice during the blazing desert heat of summer. Circular structures made of mud brick, they often rose as much as 60 feet above a massive interior ice pit. They were arranged so that cooling breezes entered them, and had an exterior groove to allow a continuous trickle of water to spiral down the outside walls, cooling the interior even further.
There was a trench around the bottom to capture any meltwater from the ice. This water would freeze during the cold desert nights, then was broken up and transported back down into the ice pits.