Naqš-i Rustam, where the Achaemenid kings lie buried and the Sasanian kings proclaimed how they had defeated Roman emperors, is one of the main archaeological sites of Iran. The oldest monument dates to the Bronze Age. No one knows why the people started to make rock reliefs on this site, but I am tempted to think that it had something to do with acoustics: there are not many places with such a beautiful echo.
Four Achaemenid kings (Darius the Great, Xerxes, Artaxerxes I, and Darius II) were buried in the rocks of Naqš-i Rustam. These men were also responsible for several other monuments, like the mysterious structure that is called “Ka’bah-i Zardusht“.
Later, the Sasanian rulers added many reliefs: in chronological sequence, the Investiture relief of Ardašir I, which became the model for several other reliefs; the famous Triumph Relief of Shapur I; the Audience Relief of Bahram II; the Equestrian Relief of Bahram II and the Double Equestrian Relief of Bahram II; the remarkable Investiture Relief of Narseh; the Equestrian Relief of Hormizd II; and finally the badly damaged Audience relief of Shapur II.