The Caravan is the town in Diablo III. It's basically a tent/wagon camp that follows the player throughout their travels, with the same Artisan/merchant NPCs appearing in each act. It's not known if the layout will vary between acts, though it's expected that the graphics will.

The tents and wagons set up in the rotting forest of gloomy Tristram Act I should look much different than the same tents and wagons in the harsh, sandy Caldeum desert in Act II, after all.