A free app for Android, by CityMaps2Go.
The Ulmon offline city map app is the most detailed city map you’ll ever find. It allows you to browse a collection of different categories of places like shops, bars, hotels, etc. It also provides information about them, like what time they open and close, or what you can find there, etc.
You can customize your maps and add your own locations as well. You can also use it to plan trips and walk around the city.
The app supports offline mode and there is no data roaming required.
The Ulmon offline city map app is very easy to use and has a lot of information.