Google's 3D City View has arrived on iOS! An update to Google Earth adds the third dimension to major locations including Washington D.C., San Francisco and Boston. At the same time, Tour Guide has been added to the platform -- swipe up from the bottom of the screen to choose from a list of notable attractions and you'll be taken straight to it, with accompanying trivia you can bore your friends with later. Given the depth-mapping necessary to power the gear, the 3D Maps are only available on the iPhone 4S and thir