When Swiss photographer Gus Petro took a trip to the United States last year, he was struck by the juxtaposition of "emptiness and density."
Petro is used to seeing plains and mountains (staples of Switzerland's landscape), but massive skyscrapers in the same country? "One is so full and the other so empty," he says. "One goes up, the other down."
Petro came up with a clever way to highlight this phenomenon during his visit to the Grand Canyon, one week after seeing New York City. The "contrast between the two was so strong and overwhelming that I had to express it somehow," he says. So he created a photo project he calls Merge.
To make it, Petro took the photographs he had of the two sites, matched their perspective points and lens angles, then put them through a process he calls "Photoshop magic."
And he's been surprised by the reaction. "After showing the images, most of the people who haven't been in either place thought it was real," he says. "They began questioning me where it is. I didn't expect that for sure."
The list skews toward larger cities and metropolitan areas along the Eastern corridor, stretching as far north as Toronto and as far south as Miami. And it looks like some of the economic incentives might be paying off.