The latest version of Google Maps for iOS released yesterday brought a number of new features. The most notable addition is support for the iPad, but there's also a really cool easter egg Google added into the app. The easter egg allows you to cache maps for off-line use inside the app. It has actually been available in the Android version for a while, but this is the first time it has made its way to iOS.
To cache your maps for off-line use, first zoom in to the area of the map that you want to save. Be careful you aren't trying to cover an extremely large area or else this trick won't wor