n photographs taken by once-secret American surveillance satellites, traces of the buried past show through the arid surface of the Middle East like pentimento. The traces are as intriguing to archaeologists as the ghostly painted-over layers on a canvas are to art historians.

Examining the pictures in detail, archaeologists have found sites of ancient settlements that had previously escaped detection. They have begun to map the vanished roads that stretched across the landscape 4,000 to 5,000 years ago.

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The new maps, archaeologists at the Oriental Institute of the University of Chicago say, are becoming important tools to understanding the geography of early urban civilization in Mesopotamia, the region embracing much of today's Syria and Iraq.

An analysis of some photographs reveals tracks of roads leading from known ruins of ancient cities far out into the hinterlands. The tracks, radiating like spokes of a wheel, define the extent of a city's reach to distant farmlands and neighboring settlements.

Other pictures show the roads linking city to city over a vast network extending from ancient Aleppo in western Syria to Nineveh, near modern Mosul in northern Iraq. Previously, scholars supposed there was some kind of road system for long-distance travel and, in the absence of better observations, simply represented the roads as straight lines between major settlements. Now they can plot the true courses of many roads.

"These intersite routes are more than connections between towns and their immediate satellites," concluded Jason A. Ur, a researcher at the Oriental Institute. "When considered at a regional level, these routes emerge as segments of larger `highways' which run from site to site on a general east-west axis."

Mr. Ur, a doctoral student, described the archaeological applications of satellite photography in an article for the spring issue of the journal Antiquity. Such pictures have been readily available since the first program of American intelligence satellites, called Corona, became obsolete and was declassified in 1995. The pictures can be bought over the Internet from the United States Geological Survey.

The pictures, Mr. Ur explained, do not show the actual roads from antiquity, but signatures of where the roads were. Shallow linear depressions, called hollow ways, were left by the repeated traffic of people and animals over centuries. This hardened the surface and caused the roadway to sink, leaving troughs that retained moisture and promoted vegetation. The roads, some up to 400 feet wide and 2 feet deep, appear in satellite pictures as subtle changes in surface growth.

A connection between these signatures and actual roadways was confirmed in ground surveys at several sites in northeastern Syria. Although a boon for research in flat arid regions, archaeologists at Chicago conceded that the Corona photography might prove to be less useful in wetter and more rugged terrain.