Analysis of a Google map led to the discovery of a Roman villa like this one in Parma, Italy.
"Using satellite images from Google Maps and Google Earth, an Italian computer programmer has stumbled upon the remains of an ancient villa. Luca Mori was studying maps of the region around his town of Sorbolo, near Parma, when he noticed a prominent, oval, shaded form more than 500 metres long. It was the meander of an ancient river, visible because former watercourses absorb different amounts of moisture from the air than their surroundings do."
edit: I tip my black hat to Mis-nagid.