The great tells of west Asia, scenes of so many romantic assaults in the early decades of archaeology, present technical problems as challenging as any: deposits to be measured by the tens of thousands of tonnes, complex stratigraphies of re-worked mudbrick. Among the tonnes are finds that run from immense buildings to tiny seals. The venture, as often as not, has its own history going back decades. How does one approach the archaeology of a tell today? Uruk, on the south Mesopotamian plain near Ur, and best known as the type-site for the 4th-millennium city, spans 5000 years, and offers an instructive example of the scale of the problem.