Act II (Diablo III)
After Act I, the story of Diablo III takes us across the sea to the area called the Borderlands. The lore on the Official Web Site mentions that this area is close to the town of Caldeum, which could mean that Caldeum will be the main town in Act II, just as, presumably, New Tristram was in Act I. In an interview for IGN, Jay Wilson, game director on Diablo III, revealed that the Act boss is Belial, the Lord of Lies.
Another area in Act II is a place called Alcarnus. Mentioned during the Monk's cinematic, it is a city that has been overrun with demons and cultists. Players will get a chance to go to Alcarnus as seen in a gameplay video.