This is the BEST app ever! I wish we discovered it earlier especially when we were in Iceland and had no wifi in the rental car. It offers offline maps of the world. Once you download the map (with an internet connection) you can get directions and routes without wifi. You can also explore your elevation and speed. We LOVE it!
We've used this app quite a bit. It has offline capabilities too, but we found maps.me to be more practical and easier to get the maps.