Qoohestan is the Arabic of Kohestan and is the short form of Kuhestan and it includes regions such as Ghaein, Tarshiz, khaf,Bakharz, Gonabad, Tabas Gilaki,Tabas Anab (mesinan) ,Bakharz, Khosf, Zam and Zave. It’s main parts of course, are south Khorasan and some cities of Khorosan –E-razavi, Yazd and the present Isfahan and cnnter of this state was Ghaein. In spite of being a part of great Khorasan in its political and official structure, its mentioned a geographically unique and independent part on its own. For natural reasons, it’s geographical condition (in strategic location of cross way of north, south, east and west), the presence of different religious and racial groups in this region has always been of importance. Qohestan in the beginning of Islamic era was known as the gate of Khorasan and was considered an important way to control states such as Khorasan, Sistan and Kerman and hence was of importance to Islamic geographical and historical experts who gave detailed reports of this region’s architecture and its elements. This research is an attempt to depict a general image of the architecture of this region in the third to the fifth century .A.H based on historical and geographical texts while paying attention to its different elements (location and situation, internal and external atmosphere, the propose of the building,typs of material and an introduction to some notable works of architecture). This research is an attempt to answer an important question which is, what was the role and the situation of architecture in Qoahestan region from the third to the fifth century .A.H based on historical sources? The present research is based on an analytical-definitional approach and has been conducted based on library sources.
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