The kidnapping of a German archeologist in late November highlighted both the historical wealth of Iraq and the perils of exploring that history. In much of the country, archeologists have all but abandoned their work because of security concerns. But officials in Kurdish-administered northern Iraq say the region is secure enough for excavations. The region is rich in potential sites, and only a fraction of them have been researched. One of the most dramatic is in the heart of Irbil, the capital of the Kurdish autonomous region.

The plains of Iraq are dotted with giant mounds that archeologists call "tals," sites that have grown higher and higher over the millennia, as people built new homes upon the ruins of older ones.

Much of what we now know of ancient Mesopotamian civilization comes from excavations of such sites.

But Iraq's archeological sites -- some of the richest in the world -- attract few researchers today. The problem is security, illustrated by the kidnapping on 25 November of the German archeologist Susanne Osthoff. She is still being held captive and will be killed, insurgents say, unless Germany breaks off relations with Baghdad.

But officials in Kurdish-administered northern Iraq say their region is safe enough for excavation work. And one fascinating place to probe is the 36-meter-high tal in the center of Irbil, a citadel that historians and archeologists say has been continuously inhabited for 6,000 years. Below the homes that now stand on the hill are the remains of ancient civilizations still waiting to be explored.

Kanan Mufti, general director for antiquities in the western Kurdish region, says that probes sunk deep into the hill have shown evidence of layers of successive civilizations. Not enough work has been done to be able to identify who exactly those inhabitants were, but among the peoples who have lived in the Irbil region are Akkadians, Sumerians, Medes, Persians, Greeks, Parthians, and Abbasids. All have been attracted by Irbil's location, on a fertile plain at the junction of two rivers and in the foothills of the Zagros Mountains.

Mufti says the successive names of Irbil give some idea of this history. Sumerian scripts refer to it as Urbylon. The Assyrians called it Arbaillo and considered it one of their most important cities. The Medes knew it Hadeap. A historian accompanying Alexander the Great named it Arbella. And the Kurds still call it Hawler, probably meaning "the place where the sun is worshipped" since the name is thought to derive from the ancient Kurdish word "helio" (sun).

As Irbil, now the capital of the Kurdish autonomous region, became the densely populated city it is now, the citadel itself became less popular, with its inhabitants abandoning their homes for more spacious apartments in the city below.