Ye Olde Fridge
Humans have always used methods other than electricity to keep our food cool, even before electronics could keep everything cold. That naturally means old-style refrigerators. This one appears to be a hill, but it isn’t.
It’s simply a filthy room that serves as insulation. This maintains heat outside and allows for a cooler inside environment as a result of the dirt covering it. That’s pretty smart from a problem-solving standpoint!