One of the world's oldest cities, built 4,000 years ago but untouched until its recent rediscovery, may reveal valuable new information about life in the Middle East's cradle of civilization.

It was called Mashkan-shapir, a walled city of some 15,000 inhabitants in Mesopotamia, between the Tigris and Euphrates rivers. In its heyday, during the reign of the great King Hammurabi in nearby Babylon, it was an important trade center and the capital of a city-state.Today, its flattened ruins, clarified through aerial photography, lie in a bone-dry desert in southern Iraq.

Pieces of cuneiform text found at the site have confirmed the city's name and the year 1840 B.C. as the construction date of the massive wall surrounding it.

Unlike other legendary Mesopotamian cities such as Babylon and Ur, Mashkan-shapir was never reoccupied after it was abandoned about 1720 B.C.

"That makes it extremely rare and valuable," says Elizabeth C. Stone, an archaeologist at the State University of New York at Stony Brook. Supported by the National Geographic Society and the American Schools of Oriental Research, Stone headed the team that found the lost city.

"Layer upon layer of later occupation covers most of these ancient sites," she says. "With our original layout intact, we hope to find out a lot more about how the world's oldest cities functioned and were organized."

Although the region is now extremely arid, aerial photographs and satellite images show the outlines of quays, harbors and an elaborate canal system that linked Mashkan-shapir to both the Tigris and Euphrates.

Paul Zimansky, a Boston University archaeologist and co-director of the project, was in charge of the photography. He got his photos by mounting a camera with an automatic timer on a kite that sometimes soared more than 800 feet above the site. Military restrictions prevented his using an aircraft.

"The site is fairly flat, and it's hard to make out much on the ground, so the aerial photographs taken from the kite have proved invaluable," says Zimansky. "We've been able to make out whole building plans of what must once have been a very wealthy city."

"Up until now, this site's only been known from historical texts," says Robert Adams, secretary of the Smithsonian Institution, who has done considerable archaeological fieldwork in the region. "Information from this place should soon have Assyriologists turning handsprings."

Trade brought prosperity to Mashkan-shapir. A palace nearly 400 feet long flanked one canal. Platforms and statuary associated with worship were found in another area of the city, indicating separation of church and state.

Occasional concentrations of copper slag and kiln wastes hint each section of the city might have had its own coppersmith and potter. "The concept of neighborhoods could have been very important in Mesopotamian cities," says Stone. "We want to test that hypothesis."

Public works were unquestionably in vogue. Sin-Iddinam, king of the city-state of Larsa, who also reigned over Mashkan-shapir, put a quarter of his population to work making bricks and constructing the wall that eventually enclosed the 138-acre city.

The king supposedly paid lavish wages for that time, according to cuneiform texts that once were embedded in the wall. He claimed each worker was paid a daily salary of 30 liters of barley, two liters of bread, four liters of beer and two ounces of lard.

The protective wall enhanced Mashkan-shapir's strategic location. Hammurabi admired the city so much he mentioned it in the prologue to his famous law code.

When Hammurabi ascended the throne of Babylon in 1792 B.C., Mesopotamia was fragmented into rival city-states. His law and his sword eventually ruled all of Mesopotamia. Mashkan-shapir surrendered to him after a bloodless siege in 1763 B.C.

Hammurabi died about 1750 B.C., and almost immediately his empire began to crumble. Revolts racked the land. About 1720 B.C., Mashkan-shapir and several other cities in the area were burned. Dikes and dams were destroyed, silt filled the canals, and a shift in the Euphrates River left the remains of the once-proud capital high, dry and deserted.