Google Earth allows you to see any location on Earth with satellite precision and it's a free app for your phone. That alone is an amazing accomplishment. Even as most smartphone owners grow used to having every piece of knowledge they could possibly need at their fingertips at all times, Google Earth manages to astound by pure scale and presentation.
Google Earth opens the same way it has for years, with a globe of the Earth, a few quick tips on how to navigate, and then a sandbox approach, allowing you to zoom in and out of any location on the planet with a few quick taps. You can zoom in to where you are at any time using the GPS in your phone and you can tilt and zoom the Earth in any direction, even flipping it upside down. You can tap on one of the recommended locations to see what Paris or Mexico City or Siberia looks like. The interface is easily one of the best of any map app on the iPhone and it is designed for exploration. The locations and satellite imagery load very fast, allowing you to zip from location to location in just seconds.
If you are interested in geography, travel, or foreign cities, then Google Earth is a must for your iOS device. The sheer number of cool things and places you can see with this app is incredible and the way Google has laid everything out makes it accessible to anyone. It's a must-have free app for your smartphone.