Natural light as the only source of light in historical buildings can play a crucial role in changing interior spaces. Iranian architects artistically directed the light beams to the interior and partitioned integrated spaces without using separation elements or materials. The main question of this study is how does sunlight create spaces within southern vault of the mosque by establishing a combination of light, shade, and darkness and what is the role of light is in spiritualization of the main altar of the mosque?. For this purpose, the light intensity was measured in the southern Shabestan and altar using devices and a 12-month light travel simulation was performed by DIALux evo 7.0 and the data were analyzed.
The results show that luminance is the highest at noon prayer time every day in a year, promoting the spiritual space of the altar. Also, intensity of the light with aforementioned functions within the vault instead of using separation walls resulted in functional separation of the spaces. The difference of the present study with previous ones is the use of photometric devices and quantitative analysis of the light in order to reach an analytical approach and to explain the importance of divine light in mosques.