The Ziggurat at Ur in Sumer

Sumerian royalty built this massive temple (called a ziggurat) in the twenty-first century B.C.E. To construct its three huge terraces (connected with stairways), workers glued bricks together with tar around a central core. The walls had to be more than seven feet thick to hold the weight of the building, whose original height is uncertain. The first terrace reached forty-five feet above the ground. Still, the Great Pyramid in Egypt dwarfed even this large monument. (© Michael S. Yamashita / Corbis.)