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Before the modern advent of the refrigerator, Persians developed a way to store ice in the middle of summer all the way back in 400 BCE. The Yakhchal was a giant clay dome that could keep food and ice below freezing for extended amounts of time, even in the blistering desert heat.
Using simplistic techniques, the buildings are domes made of clay up to 60 feet high. The fridge portion of the building is kept below ground and can store massive amounts of materials; some Yakhchals have spaces of 5,000 cubic meters.
The secret to the Yakhchal is the shape and ingredients used in the outer wall. The spiral-like shape with specially placed holes is used as a wind catcher that forces cool air down into the pit where the ice is stored, acting as a crude A/C system. And the walls themselves were made of a special mixture of select ingredients. Mortar called sarooj is made up of a specific mix of sand, clay, egg whites, lime, and goat hair. When combined and dried the compound becomes extremely resistant to heat transfer and nearly waterproof; the main secret to the success of Yakhchals.
Ice was brought down from the mountains in large quantities and stored throughout the year for the local town to use, but some of it went to royalty to keep cool and make Faloodeh, the traditional cold dessert made from noodles and lime juice.
Some yakhchals attached special wind traps called badgirs to make the cooling process even more efficient. These giant walls curved off the side of the structure and were used to make sure even the slightest breeze was making its way into the ice cache below.
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Pictures and Information courtesy of: Earth Architecture.
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