How a badgir (wind catcher) works. High velocity, high altitude wind is captured at the top of the tower, channeled to an underground water source to cool the air before releasing it to the occupied portions of the house. When water evaporates, it absorbs heat from its surroundings, i.e. it's an endothermic reaction. This property, as well as the high specific heat (thermal intertia) of earth and water and low specific heat of air are exploited in this system.