Regions
Fractured Peaks
Cold, craggy mountains with gothic cathedrals and odd monks that perform rituals.
min
Special areas
Secret cow level
Given that the past two Diablo games had secret Cow Levels, Diablo 4 will likely have one too.
Unique inhabitants and terrain
Diablo 4's five known regions will each have vastly different characteristics, like the type of monsters and NPC inhabitants, the towns' architecture, species of flora and fauna, the lay of the terrain, and weather. Even though regions are now 10-20 times larger, traveling between them should be easy using established waypoints or riding on a mount. Players will also be returning to Hell at some point in the storyline.