See Philadelphia Block by Block From Your Computer

There's something about looking at the world from above that changes your the way you think about the relationships between places. I've just discovered a couple of great sites that let you look at incredibly detailed bird's eye views of Philadelphia, right down to individual rowhouse rooftops. The easiest site is run by Microsoft, but Google Earth also has a version.

If you take a mouse-guided tour from north to south, it will quickly become obvious that the densest neighborhoods - those packed with rowhouses and no intermitant green space - are the most successful. Most of the photos were taken a year ago so they don't include the new construction that occured since then, such as Westrum's rapidly spreading Brewerytown development and the Toll Bros. project at the Naval Home,