OsmAnd is a map application that uses data from OpenStreetMap (OSM). With it, you can download high-quality maps from around the world and store as many maps as you want on your device. Keep in mind that the maps take up a fair amount of space, however, so if you download too many, you may encounter storage problems.
One of the strengths of OsmAnd is that, in addition to using data from OpenStreetMap, it also lets you access information from Wikipedia. The maps can show nearby points of interest based on information from Wikipedia.
It's important to note that the free version doesn't make use of Wikipedia to show these points of interest, and it only lets you download seven maps. The paid version, on the other hand, lets you download an unlimited number of maps that you can manage directly from the application itself.
OsmAnd is an excellent navigation tool. Not only does it let you download maps to use without an Internet connection, but it also has lots of features, including the ability to change the visual or navigation styles (according to the compass, fixed, or adjusted to forward/backward movement).