The Babylon project is Iraq’s biggest and most ambitious by far, a reflection of the ancient city’s fame and its resonance in Iraq’s modern political and cultural heritage.

“This is one of the great projects we have, and it is the first,” Qais Hussein Rashid, the director of the State Board of Antiquities and Heritage, said in an interview in Baghdad. “We want to have it as a model for all the other sites.”

The task at hand is daunting, though, and the threats to the site abundant. In the case of some of the Hussein-era reconstructions, they are irreversible. The American invasion and the carnage that followed brought archaeological and preservation work to a halt across the country, leaving ruins to wither or, in the case of looting, much worse.

The American military turned Babylon into a base. It was later occupied by Polish troops and, though it was returned to the control of the State Board of Antiquities and Heritage in 2004, the detritus of a military presence still scars the site.

The World Monuments Fund has been carrying out what amounts to archaeological triage since it began its conservation plan in 2009. It has created computer scans to provide precise records of the damage to the ruins and identified the most pernicious threats, starting with erosion caused by salty groundwater. “What we’ve got to do is create a stable environment,” Mr. Allen said at the site in November. “Right now it’s on the fast road to falling apart.”

The wicking of groundwater into mud bricks, compounded by a modern concrete walkway and the excavations conducted by the German archaeologist Robert Koldewey more than a century ago, have already eaten away some of the 2,500-year-old brick reliefs at the Ishtar Gate’s base.