Taskesen (Dashkasan), located in the Zanjan region in Iran, 15 km from the center of the city of Sultaniye, was built on the rocky slope of a hill overlooking the Safid Mountain and the plains below. The structure, which was built by carving into the rock, has a monumental appearance which is quite ruined today. There are iwans and niches with muqarnas on the side walls of the building, which consists of a square courtyard and a rectangular section. In addition, the niches on the east, west and south walls are also noteworthy. These niches are decorated with muqarnas and coarse and embossed palmetteslotuses. One of the striking elements in the structure is the large dragon reliefs on the east and west walls. It is also interesting that the dragon reliefs, which are seen in Chinese style, are similar to the depictions of dragons in the tiles in Taht-i Suleyman. Since the 1970s, some research has been carried out in the building. Until the 1990s, the floor of the structure was probably covered with rock fragments falling from the top cover and walls and soil, and the subsequent cleaning work also identified architectural fragments, such as column heads, column fragments, which can now be seen on the road leading to the structure. In addition to this example in Dashkasan, two other examples, namely the Observatory Caves and the Imamzade Masum Cave near Meraga, are carved into the rock. Particularly, a part of Imamzade Masum is considered to have a shrine belonging to the Islamic period, and the structure which was built for other functions and purposes before it has gained this function after the acceptance of Islam by the Ilkhanids. It is possible to argue about the history and function of the structure in Dashkasan. Particularly in the 13th and 14th centuries, the Mongol rule, which prevailed in the region, played a role in the interaction of ideas and practices between various cultures and religions. Related to Meraga, the fact that the historical sources indicate that Abaka Khan visited a butkhana here, and that it excited the bakhshis, and that Hulagu had previously authorized the butkhana in Hoy, brings the idea that Buddhist structures and monks exist in this region. The sources do not contain any architectural data about these structures or details of the monks' rituals. The two examples in the vicinity of Meraga given above were tried to be explained by these Buddhist traditions. It is also suggested in the historical sources that Buddhist rituals involving the Ilkhanians and bakhshi were held in the region where Dashkasan was located, and that the structure in Dashkasan could be the place mentioned in these sources. The Dashkasan example of Sultaniye is different from the Meraga examples in architecture and has monumental features. The muqarnas arrangements in the building and the herbal ornaments are seen as traces of the Islamic period of the Ilkhans. In addition to these, there is a tradition of rockcarved structures in Iran, such as the Tak-i Bostan from the Sassanid period or the Ij Mosque from the Islamic period, and parallel examples emerge in India and Afghanistan. In this paper, it is aimed to introduce the architectural and decorative features of the Dashkasan case, which has been visited and made some determinations, and to compare and evaluate them with parallel examples in Iran. Thus, the historical, religious, and cultural background of the building and the traces of the Buddhist and/or Islamic period and the function of the building have been evaluated. In this study, the principals of Ilhan, their view of religions and the development activities of the administrators depending on the religions they belong to are also evaluated in relation to the history and function of the building.