Merrill C. Tenney , Pictorial Encyclopedia of the Bible, , [1976], Vol. 5: p.1059-1061, A staged or stepped temple tower. This architectural form was developed in the third millennium B.C. in babylonia from a low temenos or platform supporting a shrine (as at Erech and 'Ugair) to the massive sevenstrory brick towers like Etemenanki "Building which is the foundation platform of heaven and earth" associated with the temple of Marduk at Babylon named Esagila ("whose top is [in] heaven") measuring 295 square ft. at the base about the same height. Access to each level was by a ramp or stairway (which some link with the ladder of Jacob's dream in Gen 28:12). On the top of this "artificial mountain" was a shrine where the god of the city was believed to descend to have intercourse with man in special rites. Several ziggurats have been excavated, those at Ur, Ashur and Choga Zambil being the best known and preserved. The "Tower of Babel" (Gen 11:1-5) might have been a ziggurat since they are top be found in all principal Mesopatamian cities.