Resembling giant earthen beehives, these unique structures in the Persian desert were used to produce something rare and valuable in ancient times: ice.

As early as 400 BC, Persian engineers built yakhchals in the desert to make and store ice. The unique structures took advantage of the low humidity in the desert, which promotes water evaporation (making evaporative cooling more effective) and rapid cooling once the sun sets.

Various design features keep the temperature low inside the yakhchal, from its spiral structure to its wind towers and vents. In some desert regions, especially at high alтιтudes, temperatures drop below freezing at night. Water is piped into the yakhchal from a qanat (a water tunnel), where it freezes when the temperature drops low enough.

Some have holes near the bottom, to keep cold air flowing down to the vast underground area where the stone is made and stored. Holes near the top of the tower let H๏τ air escape.

Yakhchals are sometimes equipped with wind towers built of mud or mud bricks. Vents at the top of the towers channel cool air into the water below. These towers are also built into the houses, acting as ventilation ducts, helping to cool them.

The bottom of the structure is where ice is stored, lined with a thick layer of straw to increase insulation.

The walls of the tower were built to cast a shadow over the water as it was channeled into the yakhchal, speeding up the freezing process. The thick, water- and heat-resistant walls were made from a special mixture of sand, clay, egg whites, lemon, goat hair, and sarooj ash.

The structure allowed people to make ice and store it during the cold months, then use it year-round to preserve food and make faloodeh, a dessert of thin noodles and frozen syrup.

Yakhchal also serves as a storage facility for ice brought down from nearby mountains, and acts as a refrigerator.

Many of these structures still exist today. Visitors can find them in Meybod, Yazd and Kerman in Iran.