They were called Yakhchal and were built in ancient Persia. Their use began around 400 BC.
They were considered refrigerators that could produce ice throughout the year even in summers with high temperatures like those of the desert.
Their use was related to preserving food and also cooling buildings.
They were made of insulating materials and at the bottom there was a space for storing ice that was under the ground. The ice placed there was transported from adjacent mountains during the winter months. In some of them, a wall was built next to them so that the building was in the shade during the day.
Today, 120 such structures survive.
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