The architecture of Iran's past periods has always been based on the application of geometric rules and principles, and this is the main reason for the richness of the drawings and accuracy in the construction of buildings. In other words, knowledge of mathematical rules and geometric drawings based on mathematics has always been considered one of the main duties of architects in the past. A subject that has received less attention in today's Iranian architecture, and the traditional and historical principles and concepts of Iranian architecture, including geometric rules and proportions, have been forgotten, and its presence in the country's contemporary buildings has significantly decreased. It can be acknowledged that geometry is one of the effective and important factors in the classification of traditional Iranian architecture. In other words, common geometric principles and proportions have been used in the design of most of the buildings that are included in a type of architecture. Among the various types of Iranian architecture that use geometric principles and proportions in their design, we can include traditional markets (Bazaars), traditional houses, mosques, caravanserais (inns), etc cited. Among the many types of architecture in Iran, traditional baths were considered one of the important urban buildings, which have always been given special attention in their design and construction in terms of stability, regulation of environmental conditions, beauty and efficiency. During the Qajar era, Qazvin was located as a city on the Silk Road, like a transportation node at the intersection of the two main axes, east to west and north to south, which hosted many travelers, merchants and tourists. It was considered obligatory to provide services to travelers as well as residents of a city that was developing. During this period, the urban neighborhoods of Qazvin expanded and their number reached twenty, and each of them independently had its own service facilities such as a mosque and a traditional bath. Traditional baths have had a special place in Iran since ancient times. The construction of these buildings for the first time in Iran has been attributed to Jamshid Shah as a myth, which evolved from the Elam period to the end of the Qajar period, and they were magnificent and beautiful buildings. During the Sassanid era, when Zoroastrian religion became the official religion of the country, traditional baths were generally built near the fire temples, because according to this ritual, whoever wanted to worship had to first purify herself with water. Especially after the arrival of Islam in Iran, due to the importance of cleaning and purification, which is considered part of religious teachings, these buildings gained special importance. Since the Pahlavi period until now, traditional baths, which used to be part of urban places and had a public aspect, by making fundamental changes in their physical structure, their proportions and dimensions have become personal and have become a part of residential interior spaces. This space has never been removed from the main spaces of a house, even with the smallest area, and today it is considered an integral part of a residential unit. Considering the number of traditional baths in the Qajar period in the city of Qazvin and also the diversity in their structure, the main questions are raised in this field, whether in terms of shape, which of the dominant geometric shapes in Iranian architecture is used for design Are the main physical components of these traditional baths used? Also, in the design of the main physical components of the above-mentioned baths, in terms of dimensions and sizes, have special proportions been observed? The general goal of this research is to discover the geometric system governing the design of the two main physical components of these buildings. In other words, the goals of this research are to investigate the main physical components of the selected samples in terms of their shape and form, as well as their classification in terms of structural pattern, and also to extract the geometric and shape system in the mentioned components in these buildings. This research is of quantitative and qualitative type and is based on interpretative-historical, survey and logical reasoning methods to analyze the architectural systems and Dimensional proportions in Sarbineh (locker room) and Garmkhaneh (sudatorium), as the two main components of these buildings in the nine traditional baths of the Qajar period in the city of Qazvin has paid. The findings of this research show that in the design and construction of the two main components of the mentioned traditional baths, different architectural systems and geometric proportions have been used with different frequencies. From these findings, it can be concluded that √3 proportion with the least frequency is observed only in the proportion of the length to the width of the Garmkhaneh' (sudatorium)' plan, and the dominant proportional pattern with the most frequency in the design and construction of these components is the square proportion, which means the presence of a "proportion 1", it was between the length and width of the mentioned spaces.
