13th century BC. The eastern most example of this typically Mesopotamian structure, the ziggurat at Choga Zambil dates from the 13th century BC, and was probably built by King Untash-Khuban. His capital city (ancient Dur Untashi, city of Untash) lay in western Iran, not far from Susa. This ziggurat is one of the best preserved examples; three of the original five staircases remain.
From The Ancient World be Giovanni Garbini