Abstract
Due to the construction of the Seymareh Dam and the risk of flooding the archaeological site ‎known as “Pir Mikail,” conducting salvage excavations at this site became an unavoidable ‎necessity. At the highest point of the mound, a stone structure with an irregular plan was ‎situated, initially hypothesized to be a Sasanian Chahartaq (four-arched structure). Accordingly, ‎the excavation was carried out with the aim of identifying the nature of the structure, ‎understanding the settlement pattern at the site, and examining the surrounding remains and their ‎interactions with one another. The present research is based on a descriptive-analytical method ‎with a field and comparative approach, as well as historical sources, and seeks to answer the ‎following questions: What is the nature of the stone structure located at the summit of the ‎mound? Is it a Sasanian Chahartaq or an Islamic-era tomb? What other remains does this site ‎contain, and what interactions and functions have these remains had with each other or with ‎other neighboring sites? What factors have influenced the formation of human settlements and ‎architecture in this region? The excavation results revealed that the main structure was not a ‎Sasanian Chahartaq but rather a tomb belonging to the middle Islamic period. In the southern part ‎of the site, the remains of a coherent architectural complex belonging to the Sasanian period were ‎identified, including spaces with barrel vaults and lime plaster coating, as well as a columned ‎hall. Furthermore, evidence indicates that this site was connected to the “Shahr-e Viran” complex ‎and a communication route. Overall, the findings suggest a continuity of settlement sequence at ‎the Pir Mikail site from the Sasanian period to the early Islamic centuries, and continued activity ‎in its central part until the late Middle Islamic centuries.‎
Keywords: Archaeology, Simareh, Sasanian, Pir-Meka’il Site, Kuhdasht.

Introduction
The Seymareh Valley has persistently attracted human societies due to its natural characteristics, strategic position, and fertile water and soil resources. This valley constituted one of the major civilizational hubs during the Sasanian and Islamic periods. Historical texts refer to it as part of the province of “Pahleh,” which comprised two principal districts: “Māsabadhān” in the north (modern-day Ilam Province), centered on the Sasanian city of Sirwan, and “Mihrajān Qadhaq” (also recorded as Qadhaq) in the south, centered on the city of Seymareh (Balādhurī, 1376/1997: 433). According to historical sources, these cities retained their significance until the early Islamic centuries. Despite the identification of numerous ancient city remains along the valley, some—such as “Shahr-e Rudbār”—have not yet been subjected to archaeological study and excavation.
The construction of the Seymareh Dam and the consequent risk of inundation rendered salvage archaeological excavations an unavoidable necessity at sites within the reservoir catchment area, including “Pir Mikā’il.” Archaeological data pertaining to the Sasanian period across present-day Iran have largely been obtained from other provinces. Recent discoveries of architectural evidence and remains in the Seymareh Valley, however, can provide a new model for settlements of this period in the Central Zagros and Lorestan regions. The studied site is located approximately at the far end of the Seymareh Valley in Lorestan Province. At the highest point of this low elevation mound, a stone structure was present, initially hypothesized to be the remains of a Sasanian Chahartaq (four arch structure). The distribution of surface sherds further confirmed the existence of occupation during the Sasanian and Islamic periods.
Excavation at this site was undertaken as a salvage necessity, with the objectives of identifying the site’s remains, determining the nature, function, and date of the stone structure, elucidating the interrelationships among the architectural features, and understanding the role and significance of these structures within the cultural and geographical context of the region. This research, predicated on the hypothesis that the aforementioned site contains previously unknown remains from the Sasanian and Islamic periods, commenced with the following research questions: What is the nature of the stone structure located atop the mound? Is this structure a Sasanian Chahartaq or an Islamic period tomb? What other remains does this site contain? What interactions and functions did these features have with one another or with other features at neighboring sites? What factors have influenced the formation of human settlements and architecture in this region?

Discussion
The most significant excavation data include:
A. Islamic Period Structure: Excavations in the central part of the site revealed a mausoleum measuring approximately 8x8 meters. The building materials consist of local natural limestone, such as large and small dressed cubic stones, sometimes irregular, along with rubble stone and cobbles, bonded with a semi-crushed, reddish-tinted gypsum mortar.
b. Sassanid Period Architectural Findings: Remains of a regular architectural complex, consisting of several interconnected spaces built with natural stone and gypsum mortar, were identified. To increase the strength of the walls, the stones were laid with gaps between them, and the empty spaces were filled with a significant volume of mortar to enhance the structure’s adhesion and resistance. Overall, the main structure includes a quadrangular space and columned halls.
c. Quadrangular Space: This refers to a quadrangular room with approximate dimensions of 360×270 cm. The discovery of arched gypsum fragments within the ceiling debris indicates that this space was covered with a barrel vault.
d. Columned Halls: Adjacent to the quadrangular space, two columned halls were also identified, each featuring a central quadrangular pier of stone and gypsum mortar acting as the middle column. Comparing this structure with similar examples suggests that the roofs of these halls were also vaulted. The internal and external surfaces of the walls were covered with a layer of gypsum plaster, 3 to 5 cm thick.
e. Enclosure Wall: In the northwestern sector of the Sassanid site, a dry-stone wall (without mortar) built with stones averaging 10×15×17 cm in size was discovered. Only one course of stones remains from this wall, which has a width of 80 cm and a remaining height of between 40 and 45 cm.
f. Remains of an Ancient Road: At the far end of the site, in its southwestern sector, parallel to the discovered enclosure wall and above the Qanat’s outlet, traces of an ancient road running northwest to southeast were identified. This road, with a width between 3 and 4 meters, ran parallel to the river and established a connection between Sirvan and Seymareh.
g. Qanat: This Qanat was identified in the southern area of the site. It transported potable water from the mountain aquifer foothills to the structures located along the banks of the Seymareh River and to the Qanat’s outlet (mazhar).
The aqueduct’s structure consists of vertical wells with an average depth of 7 meters and a gentle slope. This aqueduct channel consists of two main parts: the “arch” (with a semicircular arch and, in some parts, a “keyhole arch” type) and the “body”.

Conclusion 
Archaeological excavations revealed that the main structure in the central part of the site, contrary to the initial hypothesis, was not a Sasanian Chahartaq but rather a solitary mausoleum belonging to the Islamic period.
However, the archaeological findings in the southern part of the site include the remains of a coherent complex of spaces featuring barrel vaults, semicircular arches, and columned halls (with stone piers and semi-crushed gypsum mortar), constructed using stone and gypsum. The presence of a columned hall alongside spaces with barrel vaults constitutes a distinctive characteristic of this complex, indicating a combination of two architectural styles, both belonging to the Sasanian period. Other notable architectural features include the use of small arched openings as doorways, delicate gypsum-plastered niches on the interior walls, and the employment of simple gypsum blocks in door frames.
Considering the structural similarities with Sasanian sites within the catchment area of the Seymareh Dam—such as the materials used, arched doorways, symmetrical niches, as well as the presence of pottery sherds of the same style at the site, which correspond to typical Sasanian-period examples—a Sasanian date is proposed for this structure.
The contemporaneous functioning of the Qanat with other surrounding features provides strong evidence for the existence of an organized settlement dependent on this water system during the historical Islamic period. This Qanat not only represents a rare example of indigenous water engineering but also clearly illustrates the connection between nature, technology, and human settlements, manifesting the intelligent interaction and adaptability of human habitations with the natural environment within a historical framework.
Although a definitive statement regarding the precise function of the Sasanian structure remains difficult, its location downstream of the “Shahr-e Virān” (the ruined city) site, the presence of traces of an ancient road to its west, its proximity to the rock-cut Qanat, as well as its general architectural features and ceramic evidence, all indicate the interaction of this complex with its surrounding environment. It seems that this complex served to secure the communication route between Sirwan and Seymareh during the Sasanian and early Islamic periods. The presence of collapsed arched vaults and destroyed walls made of stone and saruj (a traditional lime-mortar) likely points to a devastating earthquake (in the 3rd century AH / 9th century CE), which caused serious damage to the Qanat and the building complex, leading to their abandonment and eventual complete destruction of the site, as well as the destruction of “Shahr-e Virān.” In sum, the architectural evidence and ceramic data confirm the settlement sequence of the site from the Sasanian period, with continued occupation into the early Islamic centuries.