Google's 3D City View is now available on iOS. The Google Earth update adds three-dimensional imagery to major locations including Washington D.C, San Francisco and Boston. It's arriving alongside Tour Guide; select a notable attraction to go straight to it, with accompanying trivia you can bore your friends with later. Sadly 3D maps requires the processing hardware of the iPhone 4S, iPad 2 or the third-generation iPad, but other iOS (4.2 or higher) device users can still get access to Tour Guide. Unsurprisingly, the update's available via the App Store -- but you shouldn't need a map to find your way there.