There is a really cool new layer in Google Earth:
“For the first time, Google has published a 3D model of an ancient city as a layer viewable in Google Earth. For decades archaeologists, students, scholars, and architects have studied the history and remains of Rome and worked to understand the city’s history. The new layer, found under Gallery->Ancient Rome 3D, depicts Rome in the year 320 AD – at the peak of its development with over a million inhabitants.” Go to the Google Earth Blog for more information. Also see the New York Times article.