Sustainable structures in Iran (natural refrigerators)
Yazd province is located in desert area in Iran.It has hot and dry climate and the temperature oscillation in summer and winter even between day and night is high.Generally Yazd has 2 seasons, long summer and short winter.Because of hot climate,in the past, in some parts of Yazd ,people built Icehouses to store ice for summer.This Ice houses consist of the ice house,dome,main wall and little pool.The dome has been built on the pool.In winter the rain water fills the pool and at night water changes to ice.Wall helps to keep ice safe from sunlight.After that ices are brought to Ice house to store for summer.

                                          source:http://www.iras.ir

However these structures have been used in the past because there were no electricity,they could be use az sustainable structure now.Therefore few changes should be implement to make it practical for present situation.For example things like easy  accessibility and also the size of structure could be change.Therefore buildings in both rural and urban areas (mostly suburb) could have it as a sustainable structure.
source:www.itto.org