Dieulafoy, who visited Iran in 1881, also reports in her travel journal: "...and then we saw a quadrilateral structure that was placed opposite the walls of the cliff. Each of its surfaces was like those of the ruined structure that we had seen in the Palvar desert..." The first illustrations of the structure were made in the seventeenth century by European tourists like Jean Chardin, Engelbert Kaempfer and Cornelis de Bruijn in their travel books; but the first scientific description and excavation reports of the structure were done by Erich Friedrich Schmidt that had pictures and illustrated blueprints. The Naqsh-e Rustam compound was first investigated and probed along with the Ka'ba-ye Zartosht structure by Ernst Herzfeld in 1923. Additionally, the compound was probed by the Oriental Institute of the University of Chicago under the leadership of Erich Schmidt in several seasons between 1936 and 1939, finding important works like the Middle Persian version of the Great Inscription of Shapur I, which was written on the wall of the structure. Application The application of the Ka'ba-ye Zartosht structure has always been controversial between archaeologists and researchers and various views and interpretations have been stated about its application; but what makes its interpretation even more difficult, is the existence of a similar structure in Pasargadae, which makes one evaluate every probability with its circumstances too and consider a similar interpretation for both. Some archaeologists have believed the structure to be a mausoleum; and some others like Roman Ghirshman and Schmidt have said that Ka'ba-ye Zartosht was a fire temple in which the holy fire was placed and it was used during religious ceremonies. Another group including Henry Rawlinson and Walter Henning believe that the structure was the treasury and the place for keeping religious documents and Avesta. A small group believes the structure to be the temple of Anahita and believes that the goddess's statue was kept in Ka'ba-ye Zartosht. Heleen Sancisi Weerdenburg believes the building to be a structure constructed by Darius I for coronation; and Shapur Shahbazi believes that Ka'ba-ye Zartosht was an Achaemenid mausoleum that was used as a site for the treasury of religious documents in the Sasanian era. Erich Friedrich Schmidt says about the importance of the structure:The outstanding effort that was necessary for creating this architectural masterpiece, was only used for building a single and dark chamber. Besides, the fact that they did or could close