Garmin Fenix (first & second generation) comes with a very basic and minimal world map, which includes major cities and suburbs around the world. The base map is only 500KB in size, which means it does not contain much information - waters, city labels, country boundaries and nothing more!
If you are looking for more detailed Garmin Fenix map, you may want to check out this link, the website owner has compiled very detailed maps (all around the world) for Fenix. Those maps have greatest level of detail - almost as much as you can get out of paper maps! However, greater details come with larger size, Fenix's processor speed isn't great, therefore it takes many seconds to draw maps of such great details. Also Fenix's limited internal storage (20MB) can only load few of them (like 5 or 8 major cities).
If you do not want too detailed local map, but would prefer a world map with greater details, I got this one for you!
Garmin BaseCamp is the software you use to load custom maps to Fenix, BaseCamp itself comes with a "basemap" of the world - it is reasonably detailed, not only contains waters/country boundaries/cities, but also the following elements:
It would be nice to have this map as Fenix's base map! However, the map is not available to transfer to Fenix straight away, but we can do something about it - now let's merge Fenix's default minimal base map with this detailed world map:
After loading this fairly detailed base map, your Fenix will still have 10MB storage left - plenty for your waypoints, tracks, or even some more detailed custom maps!