Kahgel plaster has been a common method for protecting architectural structures at the Takht-e Soleyman World Heritage Site. Primarily applied to stone and brick structures, this plaster has proven inadequate in the site's mountainous, high-rainfall climate with sub-zero temperatures, leading to significant erosion. This study investigates the potential of replacing Kahgel plaster with traditional half-baked, half-crushed gypsum plaster as a protective coating for walls and architectural remains. The aim is to prevent moisture penetration while minimizing the new coating's own deterioration. Field research, including observation and documentation, was employed to gather data. Results indicate that the use of traditional gypsum mortar as a restoration material at the site has been successful. Derived from pounded and crushed kiln-fired gypsum stone, this mortar exhibits similar characteristics to the original mortars and offers adequate strength in the region's harsh climate. Consequently, it presents a viable sacrificial coating alternative to Kahgel plaster.
Takht-e Soleyman, located in a mountainous area of northwestern Iran, is one of the country’s most important historical and cultural centers and has been studied from various scientific perspectives. This research aims to identify the environmental characteristics influencing human settlement and to examine the impacts of climatic and environmental conditions on the preservation of historical monuments. Findings indicate that the large spring of Takht-e Soleyman and several karst springs, by providing mineral-rich water, have played a significant role in the formation of settlements and the chemical composition of the soil, thereby affecting the region’s biodiversity and vegetation cover. Adequate precipitation has further enriched the vegetation and created favorable habitats for various animal species. The main objectives of this study include identifying the environmental potentials that contributed to settlement formation and proposing adaptive strategies to local climatic conditions for the conservation, restoration, and management of the complex. Given Takht-e Soleyman’s specific climate—characterized by long winters and heavy snowfall—the key question is how to ensure effective preservation of its historical assets. The research methodology is historical and descriptive-analytical, combining library studies with field observations. Comparative analysis of climatic parameters such as temperature, humidity, precipitation, and solar radiation against international standards revealed that, if properly managed, certain climatic indices can help mitigate physical deterioration of the monuments. Accordingly, practical strategies based on quantitative and qualitative indicators have been proposed to reduce adverse environmental impacts. By integrating historical, architectural, and environmental data, this study highlights the critical role of environmental studies in safeguarding archaeological sites—particularly Takht-e Soleyman—and offers scientific and practical solutions to ensure the sustainable preservation of this valuable heritage.
