The Great Ziggurat of Ur, called Etemenniguru, the house whose foundation creates terror, was commissioned in the 21st century BC by King Ur-Nammu of the Third Dynasty of Ur as a shrine to the moon god Nanna, near modern Nasiriyah in Dhi Qar province, Iraq. Its footprint measured 64 by 45 meters and it likely stood over 30 meters tall. Builders wrapped a core of sun-dried mud brick in a shell of kiln-fired brick set in bitumen, a flexible waterproof mortar. Ur-Nammu died before it was done, and his son Shulgi finished it during a 48 year reign in which he declared himself a living god, turning the temple complex into a religious, economic, and political center.

About 1,500 years later, Nabonidus, the last Neo-Babylonian king, found only a stump and rebuilt it with seven stages instead of the likely original three, borrowing Ur-Nammu’s authority for his own shaky reign. The site then sank into a mound known as Tell el-Muqayyar, the Mound of Pitch. John Taylor’s cuneiform cylinders from the 1850s identified it as Ur, and Sir Leonard Woolley’s 1922 to 1934 excavation revealed Ur-Nammu’s base beneath Nabonidus’s layers. In the 1980s Saddam Hussein rebuilt the lower facade and grand staircase, and the 1991 Gulf War left more than 400 bullet holes and four bomb craters nearby.

• Why bitumen, the same substance used on modern highways, kept a mud brick mountain from dissolving in floods
• William Loftus first noting the site in 1850 and preliminary work by Reginald Thompson and Henry Hall
• The joint University of Pennsylvania Museum and British Museum expedition that read two eras in the brickwork
• How to tell the smooth 1980s reconstruction from the rough Neo-Babylonian brick at the top
• The planned Ur Tourist City and Christian pilgrims drawn by the site’s link to the patriarch Abraham