When you visit historical architectures in Iran you will confirm that they plan everything and there are many thoughts behind their design. Specially in desert cities in the middle of Iran such as Kashan and Yazd that people have access to limited resources and they have to manage it in most optimized way.
Sardab is a solution for surviving in summer time in these cities. They build a basement under ground and mostly a pool in the center with a wind tower on top of that.
Basement are is already cooler than the surface because of difference in altitude. Air circulation from wind tower and interacting with water, make a surprisingly cooler atmosphere even in the warm summers. They mostly used these places for storing their food and also sometimes living in summer time. That is a real innovation in limitation.