Contrary to the view that ancient civilizations were not always as advanced as today’s humanity, many scientists have collected a number of examples to prove the advancement in the way of thinking of ancient people.

There are many times when ancient people were incredibly clever when it came to inventing technology to use in their daily lives. For example, the Incas had no writing system, but they did have the quipu – a counting device made of rope and knots that helped them keep track of their population and livestock, and even recorded their folk tales.

Technically, the intricate architectural wonders of the ancients are still found across most continents, from the pyramids of Egypt to underground cities like Derinkuyu in Türkiye’s Cappadocia region.

Another great example of ancient ingenuity lies in the Middle East, one of the cradles of human civilization and culture. Here, around the 4th century BC, the ancient Persians invented something called the Yakhchal, an ancient refrigerator.

In 400 BC, Persian engineers mastered the technology of storing ice in the middle of summer in the desert. Ice was brought in from the mountains in the winter and stored in Yakhchals , or ice cellars. These ancient ice “refrigerators” were used to store ice and food for use in the summer. Additionally, these ice blocks were used to treat members of the royal family.

Yakhchal – ancient Persian refrigerator.

A floating structure, the ice cellar – a “refrigerator” made of a mud-brick mixture, is dome-shaped. It reaches a height of about 18m. Inside the cellar, people dig a deep underground pit, about 5000m ³ wide , for storage. Yakhchal has mud-brick walls up to 2m thick at the base, made of a mixture of sand, clay, egg white, lemon, goat hair, and ash in moderate proportions. This mixture has the effect of preventing heat transfer and waterproofing.

Yakhchal works like this: a ganat, a system of underground channels, transports water to the ice cellar, where it freezes at night. The ice is then broken up and stored in separate vaults, where it can be easily removed when needed.

Most yakhchals have a wall built on the south side to keep the sun out and keep the ice cellar shaded.

Many yakhchals operate on a slightly different principle. Large blocks of ice are moved down from the mountains in the winter and stored in ice cellars. As the ice melts, channels under the cellars trap the water, and it refreezes at night, making it easier to transport.

Yakhchal drawing.

In the cellar, people dug a deep hole underground, about 5000m3 wide, ^to store things.

The space inside the yakhchal.

Most yakhchals have a wall built on the south side to keep the sun out and keep the ice cellar shaded. Tall towers, called Badgirs , are used in the ventilation system. By circulating hot air from the ground and cold air from the ice cellar, the badgirs act as a thermostat, regulating the temperature inside the yakhchal.

These types of yakhchals are found in abundance in modern-day Iran.