The ice house - a yakhchal - is an ancient natural refrigerator.

Above ground, the structure had a domed shape, but had a subterranean storage space; it was often used to store ice, but sometimes was used to store food as well.
The subterranean space coupled with the thick heat-resistant construction material insulated the storage space year round.
These structures were mainly built and used in Persia. Many that were built hundreds of years ago remain standing.