Geography
Authors of epic Fantasy novels often start with a map. Similarly, designers of virtual worlds often choose a map as the first concrete realization of their dreams. In any venture that has place or travel at its core, a map is the natural starting point. In constructing a map, not only are ideas given form, but new ideas are suggested. It’s unlikely that a designer will create a map only to go back and change it later to account for details that have arisen from fleshing it out. The design process rarely backtracks over maps, and therefore they’re an excellent way to begin developing content.
Virtual worlds have a more practical reason for doing maps first, in that there are technical constraints in operation. If the programmers insist on a zone-based approach, for example, that directly affects the topography of the world; if the designers want 200 zones, that affects the topography of the network the operations team has to support.
Geography is therefore where designers usually begin to turn their concepts into (virtual) reality.