Android : Offline Tourism Guide or GPS Navigator for only 3 cities

I want to develop an app for android and IOS like Sygic GPS Navigator for only 3 cities to work offline I want to enter places in map and update it time to time user may get directions to wherever they want

what can I need to start? and where should I get maps to work offline?

I know how to program in Android and IOS, I just need to know the basics of doing such thing like what technologies should I use..

I will be glad to hear any idea :)