Yakhchal: Ancient Refrigerators (2009)
This article nowhere mentions how they actually work. The article has that "ancient mystery" vibe about it that I find so annoying about pop archaeology. Googling it reveals they use evaporative cooling, which has also been used at many places and times in history, probably independently discovered, which makes it more interesting to me than glossing over how it works.In short, the WikiPedia article about yakhchals is much more satisfying: https://en.wikipedia.org/wiki/Yakhch%C4%81l