Looking at the dictionary's description above, one can in the most basic ways formulate an image of what a ziggurat looked like. However, ziggurats spanned from the simplest base which a temple sat upon, to marvels of mathematics and constructions, spanning several terraced stories and topped with a temple fit for any God.
An example of a simpler ziggurat is the White Temple of Uruk, in ancient Sumer. It was most likely constructed around 400-300 B.C. The ziggurat itself is the base on which the White Temple is set. Its purpose is to get the temple closer to the heavens, and provide access from the ground to it via steps.
Example of an extensive and massive ziggurat is the Marduk ziggurat, or Tower of Babel, of ancient Babylon. Unfortunately, not much of even the base is left of this massive structure, yet archeological findings and historical accounts put this tower at seven multicolored tiers, topped with a temple of exquisite proportions. The temple is thought to have been painted and maintained an indigo color, matching the tops of the tiers. It is known that there were three staircases leading to the temple, two of which (side flanked) were thought to have only ascended half the ziggurat's height.
The Sumerian name for the structure was Etemenanki, meaning "The Foundation of Heaven and Earth." Most likely being built by Hammurabi, the ziggurat's core was found to have contained the remains of earlier ziggurats and structures. The final stage consisted of a 15 meter hardened brick encasement constructed by King Nebuchadnezzar.