… either on iOS or Android or any other OS.
Mine are the following
1 - **CityMaps2Go **-- Provides you with navigable maps while you are offline. All you have to do is to download the map of the city before your departure and voila… use it to find sites and places (restaurants, shops, famous areas) in the new city without any data connection. With GPS turned on, I used it to navigate streets of Lisbon last year. But using it with GPS continuously will drain the battery of your device rather quickly, so use it only when you need it. The free version allows only limited map downloads. I got my Pro version for free during last Christmas. 
2 - **TripAdvisor **-- This app provides the same experience as its website. Near Me Now feature helps you locate interesting places near your location. I use it mostly for reading reviews or recommendations posted by fellow travellers. Comes free so can’t complain!
3 - **Tripomatic **-- Lets you create your trip itinerary by giving you a list of places during your trip to a city. For example, if you create a trip for Paris city, Tripomatic suggests a total of 169 attractions. When you tap on an attraction to visit, e.g. Eiffel Tower the app will give you a map, details of the Tower (a handy description, its address, opening hours, ticket prices, contact numbers, even the route to take from possible metro stations). You can then create your trip itinerary for each day of your visit and plan your trip with handy information at hand. However it needs data connection to work. The offline maps option is available but is quite expensive.
Other than these apps, when visiting a city I also download apps showing the map of metro & bus network (if available). So instead of carrying paper maps or looking up at the large maps displayed in station, I quietly open the app on my phone and see if I’m going the right direction. For Paris I can suggest **RATP **application, its in english and even shows you shopping deals according to your location. You can even use it to reserve a place for lunch/dinner in a restaurant from your room. A data connection is required, however.
Now its your turn 