I am looking for an Offline Maps App to be used while I do some international traveling, to avoid AT&T's outrageous data roaming fees. In particular, I am looking for map coverage of Lisbon, Portugal. There are a few apps that claim to have offline map support, but they turn out only to be a small JPEG with poor resolution when you pinch-zoom in. I am looking for a map that has equal detail to the normal iPhone maps app when you zoom into street level. I basically just want to use this to help navigate, as opposed to buying a paper map. Any suggestions would be greatly appreciated.