Ziggurats were a form of temples common to the Sumerians, Babylonians and Assyrians.  The earliest examples date from the end of the third millenium, B.C.  The ziggurat was a pyramidal structure, built in receding tiers upon a rectangular, oval, or square platform, with a shrine at the summit.

The core of the ziggurat was of sun-baked bricks, and the facings were of fired bricks, often glazed in different colors, which are thought to have had cosmological significance.  Access to the summit shrine was provided by a series of ramps on one side or by a continuous spiral ramp from base to summit.  The number of tiers ranged from two to seven.  Notable examples are the ruins at Ur and Khorsabad in Mesopotamia.