Abstract
Ferim, of the outskirts of Dodangeh district, is located south of Sari. Ferim had a political and military importance in the early Islamic era. Geopolitical factors, military and political capabilities should be counted among the causes of Ferim positioning. The existence of government and memorial buildings, structures and urban areas show the prevalence of the triple urban system in Ferim. No focused research has been performed on Tabaristans old cities. The historical sources not matching with the archaeological findings, has motivated the present study to be done. The following questions are posed in this article: What factors have involved in the formation, development and fall of the Ferim? What role did Ferim play in the political developments of the region? The following assumptions can be raised: A geographic location, being central to the surrounding villages and equipped with the due productive and economic capacities have been among the influential factors in the formation and development of the Ferim. The political and natural factors are counted in Ferims waning.  he political capital of Ferim as the ruling hub and the existence of defense and military structures indicate the strategic political and military status of Ferim. Natural and geopolitical boundary, strategic status and political-military position are the most effective factors in the formation and development of the city. The location of Resket Tower and the Shahneshin site covering an area of 1000 m2 and the discovery of surface cultural evidence demonstrates that the dynamism and urban life of the old city should be searched in the mentioned site. Comparing the plan of the Shahneshin with some contemporary and more ancient constructions implies that this state building played a dual role, that is called “mosque-house” in the architecture of early Islam in Iran. The political and natural factors are the reasons behind Ferims fall in the end of the 5th and 10th century of Hijri calendar.
Keywords: Ferim, Gharan-Kooh, Espahbadan, Capital, Resket Tower, Shahneshin.

Introduction
In different historical periods, the formation of cities was under the influence of diverse factors, among the most important of which suitable natural location, political, military and defense factors, economic, commercial and religious factors can be denoted (see: Orooji & Alipour, 2013: 21). Islamic cities were viewed as the direct inhibitors of Sassanid methods of urban development (Mehr-Afarin, 2014: 81). On the other hand, despite the spread of Islam in Tabarestan, the presence of native clans following the suit of the interactions and mechanisms of the Sassanid period led to the social relations and policy-making practices in this region to be a combination of Sassanid approaches and Islamic traditions.
In Tabarestan, besides the aforementioned sites and contexts, the natural and defensive fortifying factors were critical in the cities being built and located. Thus, in the feudalism era, due to the distinctive strategic and military capabilities of foothills, the cities of the region were predominantly constructed in such sites. In many cases, such cities did not need large castles and towers, ramparts, and high lookouts, as well as upkeep costs, because the inaccessible locations and impassable roads hampered the invading forces to easily access them.
Amid this, despite being pointed out in numerous sources and in the existing historical evidence, the city of Ferim as a highland in old Tabarestan (in the territory of present-day Mazandaran province) is of the cities about which few studies and excavations have been done. At the same time, lack of sufficient information about the political, military, defense functions, urban organizations and other structural features of this city and this information not being compatible with the limited archaeological findings requires dealing with such issue. This requirement gets more decisive - considering the presence of the local ruling clans (Espahbadan), -at least since the Sassanid era- in the region and their conflict or appeasement with the central governments under the supervision of the Islamic caliphs or trans-regional forces.
The main objectives of the current study are to get a picture of the urban potentials, the effective variables in the urban formation and development, the most important discovered works and their functions, to sketch the spatial organization of the city and study the determining factors in the collapse of the city of Ferim.

Study Data 
Ferim, an ancient city in Qaran-kooh in the southern part of Old Tabarestan, located 60 kilometers south of Sari, which has been mentioned as the capital of Espahbadan, city, castle, borough and region in the sources (unknown author, 1993: 147; Ibn-Hawqal, 1987: 119; Etemad-Al-Saltana, 1994; 102; Rabino, 1964: 226) was the residence of Karen  clan rulers since Sassanid dynasty, after the collapse of which it was governed by their descendants (Ibn-Hawqal, 1987; 119; see: Istakhri, 1961: 169). 
The existence of some structures such as palace, local bathhouse, square and jam-e mosque in Ferim (Ibn-Esfandyar, 1987: 156; Rabino, 1964: 226) stresses the urban and political status of Ferim among countless surrounding villages and the rulers. The coin minting in Ferim  indicates the political legitimacy of Espahbadan dwelling in Ferim and the unique economic position of this city among its bordering towns and villages in the 4th century AH.
The most important factors influencing the formation of Ferim should be considered the natural and topographic ones, the geopolitical factors and economic potentials.
Today the evidence of the urban life of Ferim can be seen in two in situ structures: The Resket Tower from the early 5th century AH (see: Figs. 1 and 2) and Shahneshin building from the mid-4th century AH (see: Plan 1; Figs. 3-6). The surface cultural evidence in the site of the mentioned monuments strengthens the chances of the existence of the old city of Ferim in this region (see Abedini, 2007: 261; Abedini, Nikoobayan and Shirzadi, 2014: 389; also Plan 2). Comparing the plan of Shahneshin with its preceding or contemporary buildings demonstrates that this structure cannot be the Jam-e Mosque mentioned in the sources and posits the theory of this dual-purpose building. 

Conclusion 
The ancient city of Ferim, as a castle, the capital and the governing base of Al-Qaran rulers, was the treasure house, the military camp and the military barrack of the survivors of the Sassanid clans from the historical era to early Islamic centuries. What makes this mountain city remarkable and creditable was its strategic location as the headquarters and capital of local kings. Despite the loss of the urban status of Ferim before the mid centuries, the existence of Ferim in the cartographic sources demonstrates the continuing social life of this city within centuries.
Several factors influencing the formation and development of the city of Ferim include the natural and topographical location, geopolitical location and inherent security, maintaining a reasonable distance from other political bases, political and geographical status, and dynamic agricultural and animal husbandry oriented economy and production potentials.
The existence of the Resket Tower monument and the discovery of the Shahneshin site in addition to finding the cultural evidence in the vicinity of the tower emphasizes the presence of a dynamic city with an approximate thousand-meter radius from the Shahneshin site .No similarity between the plan of Shahneshin and that of the primary Iranian mosques and allocating a ritual space in the heart of a complex called the ruler’s palace or the governing headquarters supports the hypothesis behind assigning Ferim Jam-e Mosque to the Shahneshin site and the mosque-house theory.
From the end of the 5th century AH, Ferim gradually lost its previous prestige and glory. The reason for the decline of Ferim should be sought in the following factors: the political factors and transferring the capital from Ferim to Sari in 486 AH, two major earthquakes shaking it in 521/506 and 700 AH, the emergence of the powerful Safavid dynasty in the 10th century, and integrating the countrywide political-military system.
Espahbad of Tabarestan, Espahbad of Qaran, the son of Sukhra, residing in Ferim stresses the irreplaceable political status of this city during the early centuries. The interaction between the citizens of Tabarestan with each other and with the officials of Royan in the serious political-government decisions indicates the critical role of the mentioned cities, particularly Ferim, in the political organization of Tabarestan of that period.