The study of the gates of the Achaemenid citadels with the new mythological approach and historical analysis method led to the discovery of concepts behind this body which refer to the cultural themes in this period which had been formed based on belief and mental patterns of the people of this period, that is, the myths. The result is that these palace-gates had a different structure from the gates of cities in other cultures and gradually underwent changes from Pasargadae to Susa and Parseh. A comparison of these gates and their developments shows that as the Achaemenid kingdom gained more power, the architecture of these buildings were formed more based on Iranian cultural themes; As in Pasargadae Gate-Palace, the influence of Egyptian and Mesopotamian culture is more evident than other gate-palaces, and in contrast the gate-palace of Parseh Citadel, which was built at the height of Achaemenid domination, without the need to refer to other cultures relies on Iranian themes; In this Gate-Palace, on one hand with its three doorways and ornaments which are a reference to Dumezil's tripartite ideology of Indo-European societies, and on the other hand with its special naming, the gate of all nations, its function is emphasized, a function that in a double-sided way refers to a gate that is open to all nations under the rule of the Achaemenid dynasty, and also It contains a symbolic connotation of the all-encompassing power of the Achaemenid rule, which encompasses all nations of all races under its governance.