DubConqueror: One of the smart things to do with a smart phone is indeed leaving the internet off. I you turn off mobile data, wifi and bluetooth and location (your GPS) as well, you can last far longer on a single battery charge. On the Fairphone forum, people complained about battery life being less than 8 hours, but with anything but the ability to make phone calls switched off and the phone mostly on stand-by if I don't use it as an mp3-player, my Fairphone 2 lasts me 5 days on a single battery charge, just like my Nokia 1100 used to do.
Good offline app to use, but you do have to visit Google Play and afterwards download the maps from within the app using the internet, is Maps.me. Very detailed maps, when walking through the forests I noticed even smaller paths are included on the map, very handy for taking a walk, but it has highways etc. as well for when you're in a car. Has maps for all of Europe, so I expect good maps for Greece as well.
I was actually looking at the Fairphone for when my BBZ10 dies.