Tucson is being stretched across the desert like toffee.
As malls and adobe homes spread outward from the city, the urban core is being stretched thin. The open-space living conditions and suburban shopping centers are a trademark of what some urban experts believe the cities of tomorrow will look like.
One of the oldest of US cities is taking on the shape of the newest of urban frontiers: an area with several regional ''nodes'' of commercial activity and employment instead of having skyscrapers and commerce centered downtown.
The urban sprawl -- Tucson encompasses twice the area of Boston -- makes mass transit and policing difficult. But the city is now trying to revitalize the urban center and encourage denser living conditions.
Several new housing projects are underway near the downtown. A doubling of office space - some 800,000 square feet -- is envisioned in the city over the next 15 years. But there are no grandiose blueprints to try to make the downtown the dominant commercial center. Instead, it will serve more specialized functions. ''We see it becoming more of an office-service center, as well as the legal and financial center of the area,'' says Wayne Moody, chief city planner.