Use of Procedural Content Generation Methods
Importantly, the team is working hard to make the random dungeons feel less generic than in the last game. The new art direction is a big part of this, and dungeon environments will be more varied in layout and design, often with sheer drops to help make the areas feel more epic, with more detail in terms of furnishings and other elements. Monster design will be a big part of giving the dungeons more character — seeing the undead scaling sheer walls out of the mist, for example, is pretty memorable.
And to clarify, our exterior zones have static borders, roads, and town placements. Most of the area in-between is static too, but there are these chunks of the map in various shapes that are essentially cut out. We then create pieces to fit those shapes and sizes, a bunch of them for each, and the game randomly picks which ones to use. They could have quests, little events, mini-bosses, just different scenery, or whatever else we want to cook up in them. It keeps the exterior locations static, while still having some random bits in there to keep them fresh. We refer to it as the adventure system.
And to clarify on THAT in case anyone hasn't been following along much, we keep our exteriors static for the most part because following the edges of the map to find exits and find where the town/questgivers are just wasn't a fun use of randomization. You also couldn't easily or quickly meet a friend anywhere outside of town because nothing was ever in the same place. And lastly it helps us create a sense of a world that actually exists, the towns and cities and at least the important points of interest exist in stationary locations.
The dungeons, in addition to being random in design and flow, also use the adventure system to bring in random events and quests.
Diablo III - Wikipedia entry for Diablo III.