Urban underground development an overview of historical underground cities in Iran

The increasing rate of urbanization and rate of population growth over the 20th century has led to various problems such as traffic congestion, air pollution, and lack of open and green spaces that have affected the cities and their citizen's life. This condition has led to increasing demands for more land use, homes, and work places, more public transport and mass transit systems and modern infrastructure, so new approaches must be found to better utilize space available. Considered use of underground space creates new methods for solving these challenges. The urban underground spaces have great untapped potentials. If these potentials are managed correctly, it would chip in considerably to the urban sustainable development. Nevertheless seeking of spaces and shelter within the earth is no new idea, man and animal alike have exploited the protective and insulative properties of the soil long before recorded history. During the history of communities have existed in areas all over the world including Iran, Turkey, Egypt, Ethiopia, China, North Africa, and the American Southwest, to name a few. Some of the best examples of man’s symbiotic relationship with nature are Nushabad in Kashan, Sāmen in Malayer and Kariz in Kish Island. These underground cities and Constructions offer many opportunities and lessons for underground development in contemporary cities. This study aims to discuss the ancient settlements of Nushabad, Sāmen and Kariz for their unique and creative underground space use and also explore the potential of developing underground spaces in order to achieving sustainable development . The basic hints of discussion are the physical geography and dominating forms of underground space use.