The ruins of the holy city of the Kingdom of Elam, surrounded by three huge concentric walls, are found at Tchogha Zanbil. Founded c. 1250 B.C., the city remained unfinished after it was invaded by Ashurbanipal, as shown by the thousands of unused bricks left at the site.Located in ancient Elam (today Khuzestan province in southwest Iran), Tchogha Zanbil (Dur-Untash, or City of Untash, in Elamite) was founded by the Elamite king Untash-Napirisha (1275-1240 BCE) as the religious centre of Elam. The principal element of this complex is an enormous ziggurat dedicated to the Elamite divinities Inshushinak and Napirisha. It is the largest ziggurat outside of Mesopotamia and the best preserved of this type of stepped pyramidal monument. The archaeological site of Tchogha Zanbil is an exceptional expression of the culture, beliefs, and ritual traditions of one of the oldest indigenous peoples of Iran. Our knowledge of the architectural development of the middle Elamite period (1400-1100 BCE) comes from the ruins of Tchogha Zanbil and of the capital city of Susa 38 km to the north-west of the temple). The ziggurat originally measured 105.2 m on each side and about 53 m in height, in five levels, and was crowned with a temple. Mud brick was the basic material of the whole ensemble. The ziggurat was given a facing of baked bricks, a number of which have cuneiform characters giving the names of deities in the Elamite and Akkadian languages. Though the ziggurat now stands only 24.75 m high, less than half its estimated original height, its state of preservation is unsurpassed. Studies of the ziggurat and the rest of the archaeological site of Tchogha Zanbil containing other temples, residences, tomb-palaces, and water reservoirs have made an important contribution to our knowledge about the architecture of this period of the Elamites, whose ancient culture persisted into the emerging Achaemenid (First Persian) Empire, which changed the face of the civilised world at that time.