Susa is located in what is now south-western Iran. The site was occupied before 4000 BC so already had a long history by the time of Cyrus the Great. During the Achaemenid period Susa was the empire's most important administrative centre and an end-point of the famous Royal Road, which ran west to Sardis in western Turkey.

Darius I undertook a lot of construction work at Susa and built his first major palace there. An impressive Persian Apadana (audience hall) had elaborate stone columns topped with capitals in the form of two bulls back to back. To the south it was combined with mud-brick buildings round four courtyards where there was extensive use of panels of brightly coloured glazed bricks. These panels showed files of guardsmen, lions and sphinxes. The guards wear richly patterned Persian dress, grasp an upright spear in both hands, and carry bows and quivers. In addition, some of the stairways were decorated with glazed brick panels showing priests or servants in Median and Persian dress bearing food and animals. All the bricks have fitters' marks to show how the builders should place them within the panels.

The site was used by rulers throughout the Achaemenid period: Artaxerxes I did restoration work on the Apadana and also built himself a palace somewhere at the site.