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Younespour M, Khanali H, Azizifar G. (2026). Functional and Architectural Study of the Earthen Fortress of Khollar in Gilavan, Khalkhal: Fortress or Caravanserai?. Athar. 47(2), 69-88. doi:10.66224/Athar.1897.2190.1
URL: http://athar.richt.ir/article-2-2153-en.html

The Gilvan Mud-Brick Fortress, located in the Shahroud District of Khalkhal County, is a notable specimen of mud-brick architecture in northwestern Iran. It is situated along the communication route connecting Khalkhal, Shal, Masal, and Masuleh. The structure features a quadrangular, rectangular plan, thick walls, and six circular turrets. Due to its distinctive form and construction, it is locally referred to as a “fortress” (qaleh). The present study aims to identify the original function of the structure and to correct its nomenclature. It adopts a descriptive-analytical approach, drawing upon data obtained from field surveys and comparative studies. The main research questions are: What are the architectural characteristics of the Gilvan Mud-Brick Fortress, and which defensive or service-oriented architectural models do they most closely align with? Can this structure be classified as a military fortress, or was it originally a roadside caravanserai with a dual function? The findings suggest that although the structure includes watchtowers, it lacks several key elements of military architecture, such as a moat, fortified gates, and extensive defensive spaces. Nevertheless, an analysis of the region’s historical developments indicates that the Khalkhal–Masuleh route primarily served military and refuge purposes prior to the Safavid period. Moreover, since Gilan was a region independent of the central government, it had limited commercial interactions with the Iranian plateau. Therefore, it can be argued that the structure conventionally known as the “Khalkhal Gilvan Mud-Brick Fortress” was originally a military-control installation (a ribat or border fortress). Following the political integration of the region in later periods, a service-oriented caravanserai function was subsequently added to it.
Keywords: Khollar Earthen Fortress Gilavan, Safavid Period, Caravanserai, Fortress, Khalkhal.

Introduction
Fortresses and caravanserais represent two significant architectural typologies within Iran’s built heritage, each reflecting the political, economic, and social dynamics of their respective historical periods. During the Safavid era, in particular, the expansion of communication and trade networks, accompanied by governmental initiatives to improve roads, led to the structural diversification and proliferation of caravanserais. These buildings served both service-oriented functions (accommodation, storage, and logistics) and protective roles in safeguarding routes (Kiani, 1970). However, historical texts and archaeological research indicate that the Khalkhal–Masuleh route (and consequently the Gilavan region) had a primarily military and refuge function until the pre-Safavid period. Gilan was among the regions independent of the central government, and little commercial or economic exchange took place along this route. The name “Gilavan” (probably composed of “Gil” + “ban”), meaning “protector of Gilan” or “defense base of Gilan,” supports this military background. This route was mainly used for escape, refuge, or launching attacks on other regions. A comparative study of trade routes in northwestern Iran shows that the most important communication route in the region was the “Caucasus Road” (a branch of the Silk Road), which passed through Firoozabad, Khalkhal, Ardabil, and the Moghan Plain to the Caucasus. Historical geography texts (including those by Ibn Hawqal, Muqaddasi, Yaqut al-Hamawi, and Hamdallah Mustawfi) mention this route as a connection between Azerbaijan and Gilan (Khanali et al., 2016: Table 2, p. 16). However, until the pre-Safavid period, this route had a primarily military function, and Firoozabad Castle (Qabaq Castle) in the Kowsar region, acting as the ruling seat of Khalkhal, played a key role in providing security and control over the route (Ibid: 4-5). From the Safavid period onward, following the political integration of Iran and increased road security, numerous caravanserais were built along this route (such as the Shah Abbasi Caravanserai, Aria Chai Caravanserai, and Yam Caravanserai). Thus, the central research question arises: Do the architectural and structural characteristics of this monument, considered in relation to its historical context and local communication networks, indicate a fortress, or rather a roadside caravanserai with a composite function? To address this question, the analysis proceeds through three concurrent approaches: 1) an examination of architectural features, including the plan, towers, construction materials, gateways, and auxiliary facilities; 2) a comparison of these features with established typologies of caravanserais and fortresses in historical and architectural studies; and 3) an assessment of the monument’s strategic location and its spatial relationship with regional trade routes. Previous research demonstrates that a strict dichotomy between “defensive” and “service-oriented” structures is often untenable in historical contexts; instead, the analysis must focus on the interrelationship of functions and the degree of priority assigned to each within the architectural and contextual framework.

Discussion
The architectural and functional analysis of the structure known as the Earthen Khollar in Gilavan suggests that this building represents a transitional typology between defensive fortresses and roadside caravanserais in northwestern Iran. An examination of the layout, construction materials, and spatial organization indicates that the building was constructed in two main phases, reflecting a change in function over time.

First Phase (pre-Safavid or early Safavid) Military-Controlling Structure
In this phase, the main enclosure walls, corner towers (with an average diameter of 8 m), and the rectangular plan of the building were constructed using chineh (rammed earth) materials. The thickness of the walls, the placement of towers at the corners and the middle of the eastern and western sides, and the strategic location overlooking the communication route all indicate a design aimed at military control and route surveillance. During this period, the Khalkhal–Masuleh route primarily served refuge and military functions, and Gilan, as a region independent of the central government, had limited commercial interactions with the Iranian plateau. Therefore, this structure can be considered a type of border ribat (a frontier hostel-fortress) or road-fortress (qal’eh-ye rahdari), whose primary function was to provide security, control traffic, and prevent incursions into surrounding areas. 

Second Phase (late Safavid or early Qajar) Change of Use to Service-Residential
In this phase, with the political integration of Iran during the Safavid period and increased road security, the Khalkhal–Masuleh route gradually gained a commercial function. Simultaneously, additions were made to the building, indicating a change in use from a purely military structure to a space with service-caravanserai functions. The most important evidence of this phase includes: the use of standardized baked bricks (26 × 26 × 7 cm) in parts of the eastern wall and southern facilities; the construction of the single northern tower (Tower No. 7) with a diameter of 4 m (half the size of the main towers), located outside the original enclosure and aligned with the main entrance—its materials also consisting of the baked bricks from the second phase; due to its small diameter and separate location, this tower served a light guarding function and entrance route surveillance rather than heavy defense; the presence of six openings in the northern half for wooden beams, which indicates two stories and a watchtower-residential function; and the reconfiguration of the interior space (although partially destroyed) toward an open central courtyard, peripheral rooms, and a standard entrance (4 m wide), all of which are characteristic of Safavid caravanserais. Thus, the northern tower is interpreted not as an independent defensive element, but as an addition designed to adapt the building to its new function. In this phase, the building maintained a limited defensive capacity (a concept known as “passive defense”), but its functional priority shifted to service-residential facilities for travelers and trade caravans. The addition of this tower during the second phase is not interpreted as an increase in military capacity during the Safavid period; rather, it represents an adaptation of the building’s structure to its new caravanserai function and a response to the supervisory-service needs of that era.
From a functional perspective, the defensive elements, including the corner bastions, appear to have played a complementary role rather than representing a primary military function. The relatively modest scale of these features, the absence of large-scale military infrastructure (such as armories or extensive moats), and the proximity to a trade route support the interpretation that the building’s primary role evolved from a military-controlling structure into a fortified caravanserai. The juxtaposition of defensive and service-oriented elements demonstrates the concept of “passive defense” in Safavid roadside architecture, whereby security measures were integrated without compromising the functional accommodation and commercial objectives of the site. Furthermore, the local name “Gilavan” (meaning “protector of Gilan”) provides evidence of the building’s military background. Therefore, the local designation “Earthen Fortress” is used not merely because of its physical fortification, but because of its original military function. The surrounding landscape, including open terrain and adjacent Islamic cemeteries, provides additional context regarding the site’s long-term use, indicating a continuity of human activity and social function beyond military concerns. This combination of architectural, functional, and contextual evidence situates the Earthen Khollar in Gilavan within a broader network of ribats and fortified caravanserais, reflecting regional strategies for controlling trade routes while accommodating travelers, and underscoring the adaptive and multifunctional nature of Safavid roadside architecture in northwestern Iran.

Conclusion
Based on field evidence, architectural observations, and comparative analysis, the Earthen Khollar in Gilavan exhibits characteristics that place it at the intersection of defensive and service-oriented architecture. The rectangular layout, organized spatial arrangement, central courtyard, peripheral rooms, and controlled access points illustrate a deliberate integration of security and functional utility. The choice of local building materials, particularly earthen materials, demonstrates a consideration of both climatic adaptation and structural stability. In response to the first research question, the architectural features—including corner semi-cylindrical towers (8 m in diameter in the first phase), courtyard-centered planning, and peripheral rooms—indicate a hybrid typology that combines defensive and roadside caravanserai elements. However, the local name “Gilavan” and historical evidence suggest the priority of a military function in the early period. In response to the second research question, the absence of extensive military facilities such as armories, deep moats, or high defensive towers, together with the presence of two construction phases, supports the interpretation that the building was initially constructed as a border ribat or road-fortress (military-controlling) and later (during the Safavid period) gained service-caravanserai functions. The single northern tower (4 m in diameter) added in the second phase is not evidence of increased military capacity, but rather a standard element of Safavid caravanserais for entrance surveillance and limited internal security (passive defense). Thus, the Earthen Khollar in Gilavan exemplifies a dual-function ribat (military-service) typology in northwestern Iran, where the functional priority shifted from being military to service-oriented over time. It underscores the adaptability of Safavid architectural strategies to local conditions, providing valuable insights into the multifunctional design principles employed in roadside complexes. However, final confirmation of this hypothesis requires archaeological excavation, stratigraphic studies, and the discovery of valid historical documents (such as travelogues or manuscripts). Future research can focus on absolute chronology and a comparison with other border ribats in northwestern Iran to provide a clearer understanding of this building’s role in the regional communication and defense network.