A square tower, 12.50 m high and 7.32 m wide, made of stone bricks, faces Darius' tomb. It is called the Kabah-i Zardusht, meaning "Cube of Zoroaster" [Rubin] or "Enclosure of Zoroaster," according to Zoroastrianism: Naqsh-e Rustam, Achaemenian and Sassanian Historical Site Page 1. It imitates a similar, earlier structure at the site of Cyrus the Great's tomb.
The stone masons cut burial chambers for the kings' sarcophagi into the floors of the rectangular tomb vaults. While it makes sense, for a rock-cliff burial, to do it that way, it is still curious: The Zoroastrian religion requires burial in the open, with the body exposed to the elements. Darius refers to his Zoroastrian religion in his biographical inscriptions and it appears on the tomb surface, as well. Below the horizontal register of Darius' tomb cross is a blank space. The middle or horizontal register probably shows a depiction of a palace of Darius. Above it is a scene depicting the king at worship. He stands on a platform supported by 30 [Jona Lendering counts only 28] representatives of the nations within the Persian Empire (known through accompanying cuneiform inscriptions). The king faces a fire altar, a holy symbol of Zoroastrianism, and in front of him is another figure with a winged disk. This may represent the supreme Zoroastrian god Ahura Mazda, since fire temples were part of his worship; however, it may, instead, represent another Iranian deity: Fire was also part of the worship of Anahita [Rubin].
The tomb faces the southeast and is 22.93 m high. Access to its burial chamber is through the middle register.
To the left of the tomb is a relief sculpture from a Persian dynasty that came half a millennium after the Achaemenids. It show Shapur I, the Sassanian king (c. A.D. 241-272) who was victorious in battle with Rome. The carving shows the Roman emperor Valerian making an obeisance. On the tall Cube of Zoroaster is this same Sassanian king's list of accomplishments, the Res Gestae Divi Saporis.
- Porada, Edith. "Classic Achaemenian Architecture and Sculpture." The Median and Achaemenian Periods. Ed. Ilya Gershevitch. Cambridge University Press, 1985. Cambridge Histories. Cambridge University Press. 13 November 2012
- "Naqsh-I Rustam," The Oxford Encyclopedia of Archaeology in the Near East, edited by Eric M. Meyers; Oxford University Press: 1997.
- Rubin, Ze'ev. "The Sasanid monarchy." Late Antiquity: Empire and Successors, A.D. 425-600. Eds. Averil Cameron, Bryan Ward-Perkins and Michael Whitby. Cambridge University Press, 2000.