Sistan is one of the population centers in southeastern Iran. This region is located near the Iran-Afghanistan border and is home to monuments from the Seleucid, Parthian, and Sassanid periods, which have attracted the attention of numerous archaeologists. Kooh Khajeh Fortress, the only natural feature in this vast plain, boasts a collection of monuments dating from prehistoric to Islamic times. Historical documents indicate that during the Parthian Empire, a palace with ritual and religious functions was established on the slopes of Kooh Khajeh, transforming this area of Sistan into one of the worship centers for Zoroastrians. This structure, known as Rostam Castle until around 1500 AD, has also been referred to as Gondafreh Palace, Gaspar Palace, Se-mogh Palace, and more recently as Kafaroon Castle or "Kohan Dezh."Due to the complexity of its various historical layers and the lack of research in this area, many parts of the Kohan Dezh monuments, located on the hillside of Kooh Khajeh, remain unknown. The primary focus of this study is to survey these monuments based on archaeological documents, field studies, and available evidence. The research aims to recover the physical structures of the building through structural reconstruction, as they are undergoing changes and destruction. The necessity of this research is underscored by the limited number of studies conducted on this site. This research employs a descriptive-historical and field-based methodology. The results of the study reveal that the palace's structure includes extensions added after its initial construction. These additions have led to the loss of the building's original form and structure, disrupted the proper movement system, and obscured the architectural decorations characteristic of Sassanid architecture.
