ziggurat (zĭgˈŏrăt) [key], form of temple common to the Sumerians, Babylonians and Assyrians. The earliest examples date from the end of the 3d millenium B.C., the latest from the 6th cent. 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. Similar structures were built by the Mayan people of Central America.