Archaeologists have discovered the ruins of an ancient Mesopotamian city that flourished 4,000 years ago and rivaled Babylon.

The site of Mashkan-shapir, 90 miles south of the Iraqi capital Baghdad, has not been occupied since the city was sacked and burned about 1720 B.C.The city was identified during the first six weeks of preliminary surveys earlier this year after Elizabeth C. Stone, one of the archaeologists, discovered a cuneiform inscription on a clay fragment with the name Mashkan.

"We have a whole city plan laid out there for us," said Stone, who, with her husband, Paul Zimansky, identified the site in January.

"We know where the canals were, the cemetery, the palace and religious quarters, the manufacturing area and the city wall. A complete, undisturbed city - that's what's really exciting about it as an archaeological site," Stone said in an interview in The New York Times on Tuesday.

Stone, an associate professor of archaeology at the State University of New York at Stony Brook, and Zimansky, an assistant professor of archaeology at Boston University, said the city may rank among the region's major archaeological finds of the past four decades.

Other scholars cheered the news of the discovery.

"It's always a happy day in archaeology when somewone nails down the identity of an ancient city," said William Hallow, professor of Assyriology at Yale University.

Some said the find could be as significant as the 1985 discovery of Tell Leilan, a northern Mesopotamian center that had been the seat of a power king in the 18th century B.C. Other archaeologists doubted that Mashkan-shapir would yield as much as Ebla, an ancient city in Syria where voluminous archives were discovered in the 1970s and revealed a previously unknown language.

The city survived for 300 years as a major trading and manufacturing center with a population of 15,000.