Google Earth for mobile phone lets people virtually fly around a 3D view of the world made from satellite and aerial imagery mapped onto the planets mountains and valleys. The iPhone version reproduces this core experience, downloading imagery from Googles servers as the perspective shifts and dotting the map with landmarks, photos, and other information.
iPhone multitouch screen actually made using the application easy. Dragging a fingertip across the screen slides the view appropriately, of course. Two-finger pinch gestures not only zoom in and out, but also, by adding a little twirling rotary motion, steer the views orientation in one direction or another.
Note: download will open an Apple mirror where you need to login with iTunes account