Rome's Ancient Sites Are at Eternal Peril

Weeds with stone-splitting roots. Relentless traffic belching pollution. Tourists trampling across the once palatial residences of emperors. Earthquakes and terrorism waiting to happen.

From the imposing stone bulk of the Colosseum to the romantic ruins of imperial luxury atop the Palatine Hill, the Eternal City's monuments, once pillaged by foreign conquerors, today face an array of perils old and new.

Rome's fragile ruins have the urgent attention of teams of monument "doctors," armed with such high-tech instruments as micro-cameras probing for weak spots.