Wow, this looks like great ancient cooling technology, thanks for posting! In these days of global warming, not a bad thing to pay attention to.
While reading the Wikipedia article, I got curious about this material they talked about, called
sarooj, to line the entire inside of these enormous ice pits.
The yakhchāl is built of a unique water resistant mortar called sarooj, composed of sand, clay, egg whites, lime, goat hair, and ash in specific proportions, that is resistant to heat transfer and is thought to be completely water impenetrable
And I thought, wow, that is a substance that deserves playing around with!!
If anyone wants to see how to make it, I found a video in Turkish with English subtitles, but they are making the "traditional Iranian" recipe, sans egg whites.