Dome in mosques has an indispensable relationship with other elements that gives meaning to the function and shape of Iranian mosques, but it includes solely secrets, said and unsaid materials that have put independently various issues in front of researchers. The research method of this paper has been a library method and collection tool has been articles published in scientific and research publications. This paper intends to review generalities on Iranian domes, structure of Iranian domes, double shell domes and brick domes and finally by the study of all these cases in the case sample (Sultaniye dome), it examines the form of the Sultaniye dome, one of the works remained since the Ilkhanid era in Zanjan, and tries to make clear the formation of its dome design by geometric analysis. Finally, it can be concluded that the dome as the identity of Iranian mosques has taken root in the people᾿s beliefs.
Keywords: Arc, double shell, Sultaniye dome, structure