In your trip to Iran you'll get familiar with qanat, qanat digging and the way the hardworking people would survive in desert in the past. Qanats are underground canals which bring water from aquafers to where people live and some vertical wells dug along the way from aquafer to where water comes out. These canals are the reason why people who live in desert and didn't have water sources around them, could survive in the area. The evidence shows that Iranian people have been familiar with the system of qanat digging about 3800 years ago. There are 36300 strings of qanat in Iran 11 of which were registered on UNESCO heritage sites list in 2016. 2 of the most famous Iranian qanats known universally are "Zarch" qanat which is the longest qanat in the world with the length of 72 kilometers and "Gonabad" qanat with one of the longest mother wells (the first well which is dug on top of the aquafer) which is 300 meters long. Water museum of Yazd can be the best place to learn more about qanats in you Iran trip!